radiocarbon based carbon source quantification of anomalous isotopic foraminifera in last glacial sediments in the western north pacific a previous study interpreted extremely 13c depleted excursions of planktonic and benthic foraminifera in last glacial sediments 17 500 to 25 400 cal years b p of the core retrieved from off shimokita peninsula and off hokkaido japan as evidence for periodic releases of methane arising from the dissociation of methane hydrate to better understand the formation process of the 13c depleted excursions we conducted high resolution natural radiocarbon measurements and biogeochemical analyses we found highly depleted 13c excursions ranging from 10 2 to 1 6 and 6 8 to 1 6 in planktonic and benthic foraminifera respectively most of the foraminiferal tests in these horizons were brown most likely as a result of postdepositional alteration reflecting the formation of authigenic carbonate on the surface of tests these alterations were also supported by high levels of mg calcite and the acid leaching test for anomalous foraminifera to evaluate the carbon sources in the altered foraminifera tests we quantified the relative contributions of 14c free methane derived carbon sources to the formation of authigenic carbonates in foraminifera with depleted 13c excursions using a coupled mass balance isotopic model 14c c and 13c 12c the radiocarbon ages of both planktonic and benthic 13c depleted foraminifera were approximately 600 to 2000 years older than those of normal tests from nearby horizons the relative contributions of authigenic carbonates derived from the methane oxidizing process reached to 22 wt for planktonic foraminifera and 15 wt for benthic foraminifera the 13c values of methane calculated from the mass balance model were between 29 and 68 for planktonic foraminifera and between 40 and 108 for benthic foraminifera consistent with 13c values reported for thermogenic and abiogenic methane in global methane hydrate reservoirs these data consistently suggest that methane related drastic environmental change occurred in the horizons that included 13c anomalies this study provides important information for interpreting geological records of the methane hydrate instability associated with climate

late glacial and deglacial palaeoceanographic changes at vestnesa ridge fram strait methane seep versus non seep environments abstract two cores from 1200 m water depth from vestnesa ridge on the western svalbard margin have been investigated for the distribution of benthic and planktic foraminiferal assemblages oxygen and carbon isotopes geochemical and sedimentological parameters including magnetic susceptibility total organic carbon toc and caco 3 content of the sediment vestnesa ridge is known for the presence of numerous pockmarks where methane gas is bubbling out from the seafloor one core was taken from a pockmark with active seepage of methane while the second core was taken just outside the seepage area for comparison the purpose of the study is to reconstruct the palaeoceanography and compare to published palaeoceanographic records from the area and evaluate if seepage of methane have had any impact on the distribution patterns of benthic foraminiferal species and the sedimentary environments through time the results indicate almost continuous presence of atlantic water throughout the last 43 000 years during the heinrich h1 interval ca 18 000 15 300 years atlantic water flowed subsurface along the bottom and the period stands out with the highest bottom water temperatures of the last 43 000 years settlement of a community of chemo synthesizing bivalves indicates increase in the release of methane beginning during h1 however in both records of seep versus non seep environments the distribution patterns of benthic foraminiferal species diversity and productivity of the specimens were the same indicating that seepage of methane had no influence on the foraminiferal faunas our results show that the palaeoceanographic development at vestnesa ridge was similar to the development over the western svalbard margin and the fram strait confirming previously published results we conclude that the benthic foraminifera at the methane seep site were mainly controlled by palaeoceanographic changes and associated changes in the sedimentary environment and palaeoproductivity overprinting any eventual influence of seepage of methane

faunal and stable isotopic analyses of benthic foraminifera from the southeast seep on kimki ridge offshore southern california usa abstract we investigated the benthic foraminiferal faunal and stable carbon and oxygen isotopic composition of a 15 cm push core na075 092b obtained on a telepresence enabled cruise to the southeast seep on kimki ridge offshore southern california the seep core was taken at a depth of 973 m in the vicinity of a beggiatoa bacterial mat and vesicomyid clams calyptogena and compared to previously published data of living assemblages from 714 m four reference cores obtained at 1030 m and another one at 739 m all of the reference sites are also from the inner continental borderland but with no evidence of methane seepage no endemic species were found at the seep site and most of the taxa recovered there have been reported previously from other seep or low oxygen environments q and r mode cluster analyses clearly illustrated differences in the faunal assemblages of the seep and non seep sites the living assemblage at southeast seep was characterized by abundant takayanagia delicata cassidulina translucens and spiroplectammina biformis whereas the non seep san pedro basin reference assemblage was comprised primarily of chilostomella oolina and globobulimina pacifica density and species richness were lower at the seep site compared to the non seep site reflecting the harsher living conditions there the dead assemblage at the seep site was dominated by gyroidina turgida compared to cassidulina translucens at the 1030 m non seep site and cassidulina translucens pseudoparrella pacifica and takayanagia delicata at the 739 m non seep site density was three times lower at southeast seep than at the non seep sites of comparable water depth but species richness was 30 higher stable carbon isotopic values were considerably depleted in the seep samples compared to the non seep samples with a progression from lightest to heaviest average 13c values evident at the seep site reflecting microhabitat preference and vital effect the deep infaunal species of globobulimina the shallow infaunal species uvigerina peregrina the epifaunal species cibicidoides wuellerstorfi and the shallow infaunal but aragonite shelled species hoeglundina elegans the 13c values downcore among each benthic species indicates ongoing fluid seepage through at least the last 3800 cal yr b p at southeast seep besides the continual local seepage evidence from 13c values of planktic foraminifera in the seep core suggest two pulses of methane at 3000 and 3700 cal yr b p were released that were large enough to influence much of the water column paired benthic and planktic foraminiferal stable oxygen isotope records provide evidence that there were no paleoenvironmental changes such as increased bottom water temperature or changes in oxygen isotopic composition of bottom and pore waters during this 3800 year record to induce the methane releases instead southeast seep appears to be the result of local faulting providing pathways for fluid to flow to the seafloor at a fault stepover or transpressional bend in the regional strike slip system

foraminiferal response to an active methane seep environment a case study from the adriatic sea abstractit has been analysed the taxonomic structure and isotopic composition of the cytoplasm and tests of living rose bengal stained protoplasm full and dead empty tests benthic foraminifera 63 m in surface sediments from sites with and without methaneseepage at water depths of about 25 m water in the northern adriatic sea and compared these data to isotope analyses of carbonaterocks at the same locations foraminiferal density is higher in seep samples than in control ones despite the low oxygen and highsulphide contents in sediments the 13 c values in foraminiferal cytoplasm at the seep sites are lower than those in cytoplasm ofthe same species in control samples suggesting that beggiatoa may be a food source for the foraminifera and explaining thehigher foraminiferal density at the seep site in contrast the 13 c values of tests of living and dead benthic foraminifera at seep siteswere not significantly different from those in tests of the same species collected at the control sites therefore the carbon isotopevalues of foraminiferal tests in this area do not reflect the ones of the methane seepage although the authigenic carbonate incalcareous sandstones of the methane seepage area is significantly negative and indicates the contribution of methane seepage thesimilar carbon isotope values measured in the foraminiferal tests from shallow settings of the north eastern adriatic sea seemtherefore to be independent of methane seepages 2006 elsevier b v all rights reserved

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

an enigmatic kilometer scale concentration of small mytilids late miocene guadalquivir basin s spain abstract upper miocene heterozoan carbonates crop out extensively in a ne sw trending belt 42 km long and 1 5 8 km wide along the so called el alcor topographic high from carmona to dos hermanas seville s spain these carbonates formed at the southern active margin of the guadalquivir basin the foreland basin of the betic cordillera they change to marls basinward ne and to sands landward se and sw therefore carbonate production was constrained to a limited area in an otherwise siliciclastic shelf the carbonates up to 40 m thick overlie a gradually coarsening upward succession of marls followed by silts and sandstones the carbonate sequence can be divided into three subunits corresponding from bottom to top to lowstand transgressive and highstand system tract deposits the lower subunit exhibiting extensive trough cross bedding is interpreted as a shallow water bar deposit the intermediate subunit onlaps underlying sediments and was deposited in deeper low turbulence conditions the upper subunit deposits accumulated in a well oxygenated outer platform based on benthic foraminiferal assemblages the presence of hummocky and swaley cross stratification in these latter deposits suggests that they were affected by storms pervasive fluid escape structures are also observed throughout the carbonates the three subunits consist of bioclastic packstones to rudstones made up of abundant fragments of small mytilids isotopic data from serpulid polychaete ditrupa tubes show 13c depleted values up to 16 1 whereas 18o yields normal marine values additional isotopic data on shells of scallops oysters and small mussels as well as bulk sediment show diagenetic alterations based on actualistic examples of massive concentrations of mussels the nearly monospecific composition of the el alcor deposits together with negative 13c values of ditrupa tubes indicates that cold seeps presumably promoted carbonate formation however the absence of typical features of cold seep deposits such as authigenic carbonates mediated by anaerobic bacterial activity and the typical chemosynthetic shelly organisms makes the large carbonate body of el alcor an unusual cold seep deposit

novel high pressure culture experiments on deep sea benthic foraminifera evidence for methane seepage related δ13c of cibicides wuellerstorfi in field studies of active hydrocarbon seeps the carbon isotopic composition of rose bengal stained benthic foraminiferal tests 13ctest and bottom water dic 13cdic deviates from their normal marine ratios this circumstance led to ongoing discussions on whether aerobic foraminifers like cibicides wuellerstorfi are capable of living at seepage sites and more importantly if their tests reflect the low 13c values of emanating methane to evaluate the discrepancy between 13cdic and 13ctest we conducted methane seepage emulating culture experiments on undepressurized sediments from the hakon mosby mud volcano a modern methane seepage structure that hosts living c wuellerstorfi with distinct negative 13c values the collected sediments were cultured at a site alike pressure and mean bottom water methane concentration using newly developed high pressure aquaria over an experimental period of 5 months our novel technology enabled a successful reproduction of all calcareous deep sea benthic foraminiferal species living at that site notably the first c wuellerstorfi cultured in the laboratory to show the influence of methane on 13ctest we ran parallel experiments with 99 12c and 99 13c methane in the experimental bottom water during the experimental running time methanotrophs in the water column obviously converted the experimentally added methane source to 13c enriched and depleted dic respectively since whole sediment cores were cultured it was impossible to keep 13cdic constant over the 5 month duration which is reflected in a variability of 13ctest in foraminiferal shells irrespective of that the methane source is reflected in 13ctest of foraminiferal shells and for the natural seep conditions simulating 12c experiment the mean 13cdic and 13ctest in c wuellerstorfi were equal although for future culturing experiments improvements of the experimental conditions are advisable our first results are evidence that persistent methane emanation impacts the carbon isotopic composition of deep sea benthic foraminifera

light δ13c events during deglaciation of the east greenland continental shelf attributed to methane release from gas hydrates we have documented high resolution stable isotope records from three marine cores on the east greenland shelf these records exhibit three rapid light 13c events 3 to 7 in benthic and planktic foraminifera during deglaciation that are spatially and temporally transgressive the light 13c events are associated with light planktic 18o indicative of meltwater in kangerlussuaq trough the first 13c event occurs at initial deglaciation 13 94 14 0 cal ka and the second occurs at 12 85 12 9 cal ka a younger event at 10 3 9 3 cal ka is recorded near the mouth of nansen fjord during final deglaciation the hypothesized mechanism for the light 13c is expulsion of methane from gas hydrates in the seafloor from pressure release during ice sheet retreat

foraminifera from gas hydrate bearing sediments of the northeastern south china sea proxy evaluation and application for methane release activity abstract anomalously low 13c values of foraminifera in the stratigraphy are usually interpreted to reflect activities of paleo methane seepage the application of this proxy however requires to understand the cause of anomalously low 13c signals in foraminifera here we present stable carbon and oxygen isotopes 13c and 18o mg ca ratios and accelerator mass spectrometry ams radiocarbon data from cores gmgs2 08b 0 5 5 m below the seafloor mbsf and 08c 2 23 mbsf at 798 m water depth recovered from the gas hydrate bearing sediments in the northeastern south china sea scs the main objectives are to investigate the primary versus secondary signals of extremely negative 13c values of foraminifera and further recognize the methane emission events mees the 13c values of benthic uvigerina peregrina and cibicidoides spp and planktonic globigerinoides ruber and pulleniatina obliquiloculata foraminifera in these two cores show distinct intervals with negative values as low as 15 85 that indicate the shift of the sulfate methane transition zone smtz and the change in methane release flux in the past the 13c records of u peregrina by a more exhaustive cleaning procedure designed to remove authigenic carbonate coatings show that most 13c values are still lower relative to those in the normal marine environment the mg ca ratios of uvigerina spp by this exhaustive cleaning procedure display higher values and more variable for anomalous tests as high as 13 40 mmol mol than normal ones these observations indicate the 13c depleted signals of foraminifera are mainly originated from diagenetic alteration of authigenic carbonate precipitates with extremely negative 13c values furthermore the mass balance approach is adopted to assess the relative contribution of methane derived authigenic carbonate in the low 13c signals in foraminifera and reveals the maximum contribution can be as high as 30 among the 13c anomalies additionally several major mees with distinct characteristics can be recognized according to remarkable 13c excursions of foraminifera in these two cores

living stained benthic foraminifera within surficial sediments of the skagerrak abstract an analysis of living stained benthic foraminifera within four box cores raised from water depths of 74 to 621 m in the skagerrak shows that faunal patterns at different water depths are strikingly different within this relatively shallow organicrich marginal sea environment although some genera show vertical stratification within the sediments a number of taxa are found over wide intervals or have different patterns between cores the vertical distributional data are compared with deep sea data from the eastern margin of north america benthic foraminifera from a deep core at 530 m in the skagerrak have similar faunal patterns within the surficial sediments as found in the deep sea but shallow cores at 74 and 212 m have more complex patterns this difference between shallow and deep cores within the skagerrak and the north atlantic is attributed to higher biological activity in the shallow environments which creates a greater amount of heterogeneity within the shallow water sediments than is found in deeper environments the faunal data suggest that the use of benthic foraminifera for paleoenvironmental reconstructions in shallow organicrich regions will be complicated in future studies the ecology of individual species is difficult to assess because of the complex faunal patterns observed within the surficial sediments geochemical studies for estimating bottom water oxygen or organic carbon flux will also be difficult since these studies assume that taxa occupy particular microhabitats within the surficial sediments

foraminiferal isotope anomalies from northwestern pacific marginal sediments 1 we evaluated the influence of methane release from methane hydrate reservoirs in the northwestern pacific continental margin on stable isotope values we analyzed stable isotopes of foraminifera from a piston core collected at 1066 m water depth off eastern hokkaido northern japan carbon isotope signals indicated that planktonic and benthic foraminifera in several glacial sediment layers in the core were highly depleted in 13c both the planktonic and benthic foraminiferal 13c values ranged from about 10 to 2 most foraminiferal tests in these horizons were brown as a result of postdepositional alteration foraminiferal oxygen isotopes fluctuated abnormally in the glacial sediment layers showing small about 0 5 positive shifts relative to normal glacial values we attributed the positive shifts to authigenic carbonate formation in the foraminiferal tests the authigenic carbonates have formed when rising methane from methane hydrate in the sediment became oxidized as it came in contact with dissolved sulfate near the seafloor episodic methane release events may be associated with great plate boundary earthquakes with epicenters near the coring site

response of anaerobic methanotrophs and benthic foraminifera to 20 years of methane emission from a gas blowout in the north sea highlights high abundance of active anaerobic methanotrophs in sediments of the blowout crater suggests adaptation to methane seepage within at most two decades fast exchange processes in permeable surface sediments prevent sulfate depletion and probably methane derived carbonate precipitation methane seepage impacts isotopic and assemblage composition of benthic foraminifera abstract methane emissions from marine sediments are partly controlled by microbial anaerobic oxidation of methane aom aom provides a long term sink for carbon through precipitation of methane derived authigenic carbonates mdac estimates on the adaptation time of this benthic methane filter as well as on the establishment of related processes and communities after an onset of methane seepage are rare in the north sea considerable amounts of methane have been released since 20 years from a man made gas blowout offering an ideal natural laboratory to study the effects of methane seepage on initially pristine sediment sediment cores were taken from the blowout crater and a reference site 50 m distance in 2011 and 2012 respectively to investigate porewater chemistry the aom community and activity the presence of authigenic carbonates and benthic foraminiferal assemblages potential aom activity up to 3060 nmol cm 3 sediment d 1 or 375 mmol m 2 d 1 was detected only in the blowout crater up to the maximum sampling depth of 18 cm card fish analyzes suggest that monospecific anme 2 aggregates were the only type of aom organisms present showing densities up to 2 2 107 aggregates cm 3 similar to established methane seeps no evidence for recent mdac formation was found using stable isotope analyzes 13c and 18o in contrast the carbon isotopic signature of methane was recorded by the epibenthic foraminifer cibicides lobatulus 13c 0 66 surprisingly the foraminiferal assemblage in the blowout crater was dominated by cibicides and other species commonly found in the norwegian channel and fjords indicating that these organisms have responded sensitively to the specific environmental conditions at the blowout the high activity and abundance of aom organisms only at the blowout site suggests adaptation to a strong increase in methane flux in the order of at most two decades high gas discharge dynamics in permeable surface sediments facilitate fast sulfate replenishing and stimulation of aom the accompanied prevention of total alkalinity build up in the porewater thereby appears to inhibit the formation of substantial methane derived authigenic carbonate at least within the given time window

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

influences of thermal and fluid characteristics of methane and hydrothermal seeps on the stable oxygen isotopes of living benthic foraminifera abstract the serendipitous discovery of methane seep fluids with elevated temperatures 3 6 5 2 c described as a hydrothermal seepage by levin et al 2012 has led to questions about the prevalence of this previously overlooked habitat stable oxygen isotopic analysis of cibicidoides wuellerstorfi schwager 1866 attached to tubeworms near the hydrothermal seep described by levin et al 2012 reflect 18o values consistent with elevated seepage temperatures temperature reconstructions based on c wuellerstorfi 18o from additional seeps in the pacific mounds 11 12 offshore costa rica and hydrate ridge produced variability that is likely a result of influences of seep source temperature and salinity larger ranges in 18o 0 10 paired with traditional isotopic seep indicators e g 13c 0 15 have the potential to geochemically discern whether foraminifera were calcifying in areas of active methane seepage or nearby surrounding off seep environments elevated temperatures derived from foraminiferal reconstructions at jaco scar indicate that it is possible to use foraminiferal 18o to identify the presence and extent of these recently discovered environments seep fluids with elevated temperatures may be common seafloor features and benthic foraminiferal 18o may be an effective means to detect and determine the spatial and temporal extent and possible origin of hydrothermal seepage

does the oxidation of methane leave an isotopic fingerprint in the geologic record 1 pore water co2 and 13c data are presented for the dysoxic santa barbara and santa monica basins in an attempt to constrain the influence of methane oxidation on the pore water gradients and benthic foraminiferal 13c although these two basins are adjacent to one another santa barbara basin has steeper pore water co2 and 13c gradients methane oxidation could be contributing to the higher gradients in this basin the isotope mass balance for pore water co2 indicates however that the pore water gradients in the upper 2 cm of both basins are controlled only by the rate of photosynthate carbon oxidation and the rate of diffusion methane derived co2 has no discernable influence on pore water or carbonate 13c values at these sediment depths in either basin benthic foraminiferal species inhabiting different depth horizons in the top centimeter incorporate these steep isotopic gradients in their calcite tests and can be used therefore to reconstruct the history of carbon oxidation within the basins on the basis of these modern geochemical constraints a more likely explanation for the apparent 13c excursions recorded in the late pleistocene sediments from santa barbara basin involves enhanced carbon rain and carbon oxidation in the basin sediments rather than clathrate destabilization

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

is methane venting at the seafloor recorded by δ13c of benthic foraminifera shells the research was supported by wcnurp grant pf806880 and by nsf grants oce 9731157 oce 9815186 and oce 9906944 curation of sediment cores at the osu norcor repository is supported by nsf

a study of the chemistry of pore fluids and authigenic carbonates in methane seep environments kodiak trench hydrate ridge monterey bay and eel river basin analyses of the chemical and isotopic composition of carbonates rocks recovered from methane seepage areas of the kodiak trench hydrate ridge monterey bay clam flats and the eel river basin coupled with the studies of the chemistry of the pore fluids have shown that these carbonates have grown within the sediment column geochemical profiles of pore fluids show that in deep water seeps kodiak trench 4450 m monterey bay 1000 m hydrate ridge 650 m 13c dic values are low isotopically light whereas in the eel river area 350 500 m 13c dic values are much higher isotopically heavier in all cases the 13c values indicate that processes of methane oxidation associated with sulfate reduction are dominant in the shallow sediments data on the isotopic composition of authigenic carbonates found at sites in kodiak trench eel river basin south and eel river basin north indicate a variable composition and origin in different geochemical environments some of the authigenic carbonates from the study sites show a trend in their 13c values similar to those of the pore fluids obtained in their vicinity suggesting formation at relatively shallow depths but others indicate formation at greater sediment depths the latter usually consist of high magnesium calcite or dolomite which from their high values of 13c up to 23 and 18o up to 7 5 suggest formation in the deeper horizons of the sediments in the zone of methanogenesis these observations are in agreement with observations by other workers at hydrate ridge in monterey bay and in the eel river basin

methane driven late pleistocene δ13c minima and overflow reversals in the southwestern greenland sea a core transect across the southwestern greenland sea reveals coeval events of extremely negative planktic and benthic 1 3 c excursions between 40 and 87 ka the most pronounced event event 1 began at peak dansgaard oeschger stadial 22 85 ka with a duration of 18 k y during this episode incursions of atlantic intermediate water caused a bottom water warming of up to 8 c the amplitude timing and geographic pattern of the 1 3 c events suggest that this bottom water warming triggered clathrate instability along the east greenland slope and a methane induced depletion of 1 3 c d i c dic dissolved inorganic carbon since 1 3 c event 1 matches a major peak in atmospheric ch 4 concentration this clathrate destabilization may have contributed to the rise in atmospheric ch 4 and thus to climate warming over marine isotope stage 5 1

isotopic evidence for the incorporation of methane derived carbon into foraminifera from modern methane seeps hydrate ridge northeast pacific the presence of modern methane seeps at hydrate ridge offshore oregon provide an opportunity to study the influence of methane seeps on the ecology and geochemistry of living foraminifera a series of cores were collected from the southern summit of hydrate ridge in 2002 samples were preserved and stained to determine the 13c composition of three species of live stained and dead benthic foraminifera uvigerina peregrina cibicidoides mckannai and globobulimina auriculata specimens were examined under light and scanning electron microscopy sem and exhibit no evidence of diagenesis or authigenic carbonate precipitation individual living foraminifera from seep sites recorded 13c values from 0 4 to 21 2 indicating the isotopic influence of high methane concentrations average 13c values calculated from single specimens range from 1 28 to 5 64 at seep sites and 0 81 to 0 85 at a control off seep site two distinct seep environments distinguished by the presence of microbial mats or clam fields were studied to determine environmental influences on 13c values individual foraminifera from microbial mat sites exhibited more depleted 13c values than those from clam field sites we interpret these differences as an effect of food source and or symbiotic microbes on foraminiferal carbon isotopic values acting to magnify the negative 13c values recorded via the dic pool no statistical difference was found between 13c values of live vs dead specimens this suggests that authigenic carbonate precipitation did not play a dominant role in the observed isotopic compositions however a few dead specimens with extremely negative 13c composition 12 do indicate potential evidence for an authigenic influence on the recorded 13c composition

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in monterey bay california 1 as part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release we compared ambient pore water chemistry with the distribution and stable isotopic composition of living rose bengal stained foraminifera in mbari rov ventana tube cores taken from modern seepage areas about 1000 m water depth in monterey bay california benthic foraminiferal isotopic differences between sites clearly indicate that methane influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry carbon isotope signatures of living benthic foraminifera did not conform to the very negative 30 to 48 methane influenced carbon isotope values of the pore waters they live in instead the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published 13c values of foraminifera living in nonseep habitats it is not clear what relative influences biological ecological and physical factors have on the carbon isotopic signatures observed in seep foraminifera substantial carbon isotope differences can exist between individuals of the same seep species for instance 13c values of living globobulimina pacifica varied by as much as 2 9 between seeps within 8 km of each other whereas 13c values of living uvigerina peregrina varied by as much as 1 95 within the same seep provided there is no diagenetic alteration of the test carbonate isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage

paleo methane emissions recorded in foraminifera near the landward limit of the gas hydrate stability zone offshore western svalbard we present stable isotope and geochemical data from four sediment cores from west of prins karls forland ca 340 m water depth offshore western svalbard recovered from close to sites of active methane seepage as well as from shallower water depths where methane seepage is not presently observed our analyses provide insight into the record of methane seepage in an area where ongoing ocean warming may be fueling the destabilization of shallow methane hydrate the 13c values of benthic and planktonic foraminifera at the methane seep sites show distinct intervals with negative values as low as 27 8 that do not coincide with the present day depth of the sulfate methane transition zone smtz these intervals are interpreted to record long term fluctuations in methane release at the present day landward limit of the gas hydrate stability zone ghsz shifts in the radiocarbon ages obtained from planktonic foraminifera toward older values are related to methane derived authigenic carbonate overgrowths of the foraminiferal tests and prevent us from establishing the chronology of seepage events at shallower water depths where seepage is not presently observed no record of past methane seepage is recorded in foraminifera from sediments spanning the last 14 ka cal bp 14c ams dating 13c values of foraminiferal carbonate tests appear to be much more sensitive to methane seepage than other sediment parameters by providing nucleation sites for authigenic carbonate precipitation foraminifera thus record the position of even a transiently stable smtz which is likely to be a characteristic of temporally variable methane fluxes

benthic pelagic coupling in the southern california bight relationships between sinking organic material diatoms and benthic foraminifera abstract in an effort to understand the relationship between surface water processes and seafloor sediment characteristics in the southern california bight opal concentrations organic carbon weight percent measurements diatom abundances and assemblages and living benthic foraminiferal abundances were examined in surface sediments from two sites along the continental margin of southern california although opal and organic carbon weight percentages in the top 1 cm of surface sediments reflect spatial changes in productivity between sites our results indicate that they are not sensitive indicators of seasonal changes in surface water productivity at either site the close correspondence between seasonal diatom flux in the adjacent santa barbara basin sbb abundances of diatoms indicative of upwelling conditions and opportunistic benthic foraminifera indicate that there is a rapid weeks to months opportunistic response of the benthic species nonionella fragilis to input from changes in surface water characteristics these results highlight the close association of surface water conditions and preservable microfauna and flora and confirm the influence of surface characteristics on seafloor ecosystems in bathyal environments on the california margin additional information on these associations will further improve our ability to discern seasonal and spatial changes in paleoproductivity from the geologic record

benthic foraminifera associated with cold methane seeps on the northern california margin ecology and stable isotopic composition release of methane from large marine reservoirs has been linked to climate change as a causal mechanism and a consequence of temperature changes during the quaternary and the paleocene these inferred linkages are based primarily on variations in benthic foraminiferal stable isotope signatures few modern analog data exist however to assess the influence of methane flux on the geochemistry or faunal characteristics of benthic foraminiferal assemblages here we present analyses of the ecology and stable isotopic compositions of living rose bengal stained and dead fossil foraminifera 150 mm from cold methane seeps on the slope off of the eel river northern california 500 525 m and discuss potential applications for reconstructions of methane release in the past and present calcareous foraminiferal assemblages associated with calyptogena clam bed seeps were comprised of species that are also found in organic rich environments cosmopolitan paleoceanographically important taxa were abundant these included uvigerina bolivina chilostomella globobulimina a ndnonionella we speculate that seep foraminifera are attracted to the availability of food at cold seeps and require no adaptations beyond those needed for life in organic rich reducing environments oxygen isotopic values of the tests of living foraminiferal assemblages from seeps had a high range up to 0 69 as did carbon isotopic values up to 1 02 many living foraminiferal isotope values were within the range exhibited by the same or similar species in non seep environments carbon isotopic values of fossil foraminifera found deeper in the sediments 18 20 cm however were 4 10 u peregrina and 3 60 b subargentea more negative than living d 13 c values these results suggest that d 13 c values of foraminiferal tests reflect methane seepage and species specific differences in isotopic composition and can indicate temporal variations in seep activity a better understanding of foraminiferal ecology and stable isotopic composition will enhance paleo seep recognition and improve interpretations of climatic and paleoceanographic change 2000 elsevier science b v all rights reserved

methane induced early diagenesis of foraminiferal tests in the southwestern greenland sea abstract planktic and epibenthic foraminiferal 13c records at site ps62 015 3 southwestern greenland sea reveal a series of transient events of extreme 13c depletion down to 6 during the period 90 40 ka scanning electron microscope studies of the ultrastructures of foraminiferal tests suggest that 13c depleted specimens are affected by some 10 20 overgrowth by authigenic calcite contributing to the light 13c signal incremental leaching experiments and census counts of pristine versus overgrowth affected specimens show that the 13c depleted foraminiferal tests incorporate a primary 13c signature most likely ranging from 1 to 1 7 and a post depositional 13c signature around 17 to 19 5 extremely low values of productivity and organic carbon in late quaternary sediments along the east greenland margin preclude organic matter as potential source of the isotopically light carbon in contrast thermal instability of clathrates and subsequent aerobic oxidation of highly 12c enriched methane in pore and ocean water provide a compelling mechanism to account for the negative 13c excursions of both primary and post depositional carbonates here pore water methane may have led to a supersaturation of 13c depleted bicarbonate and precipitation of isotopically light authigenic calcite on and in foraminiferal tests a feature that may serve as a tracer to former sites of clathrate destabilization

cold seeps and authigenic carbonate formation in monterey bay california abstract authigenic carbonate associated with modern cold seep biological communities and their extinct analogues exhibit a broad range in stable isotope and mineral composition within the limited geographic area of monterey bay although such variations in ancient samples have been used to infer differing tectonic settings these carbonates all formed within a faulted continental margin environment and chemical variations reflect local differences in the sources and flux of carbon to sediment pore fluids the slow seepage of fluid and with it dissolved carbon along the transform faulted continental margin results in discrete areas of enhanced microbial sulfate reduction oxidation of methane from both biogenic and thermogenic origins as well as the active precipitation of both high mg calcite hmc and dolomite the authigenic carbonates include semicontinuous pavements of shallow cemented sediments surrounding benthic communities circular or pipe like chimneys interpreted as cemented conduits formed as a result of methane gas expulsion centimeter to meter scale rings doughnuts or slabs winnowed from variable depths within sediments and carbonate veins ankerite or calcite or cements in faulted basement rocks draped with bacterial mat abundant pyrite framboids preferentially filling the tests of the benthic foraminifer uvigerina peregrina and characteristic of the hmc bearing samples are products of a zone of shallow microbial sulfate reduction a process fundamental to the nourishment of the chemosynthetic cold seep communities sites on a sedimented ridge west of the san gregorio fault zone have carbon isotopic values between 35 and 56 that are strongly influenced by carbon derived from methane the higher values of 18 o more enriched in 18 o are found closer to the active fault zone carbonates from sites within the san gregorio fault zone or from monterey canyon floor exposures of miocene sediments have carbon isotope values between 7 and 26 that are mixtures of sedimentary organic carbon and microbially oxidized hydrocarbons from organic rich petroleum source rocks dolomite bearing samples are more enriched in both 18 o and 13 c bulk carbonate samples with heavier 18 o 18 o 3 5 result from the abundance of authigenic dolomite and low temperatures of formation local destabilization of clathrates might also create pore fluids that are more enriched in both 13 c and 18 o

cold seeps in monterey bay california geochemistry of pore waters and relationship to benthic foraminiferal calcite abstract an extensive geochemical and biogeochemical examination of ch4 seeps in the clam flats area of monterey bay provides insight into the character of relationships between seep geochemistry and benthic foraminiferal geochemistry the area is characterized by sulfide rich fluids sulfide increases are associated with large increases in alkalinity as well as small decreases in dissolved ca and mg in addition only small increases in nh4 are observed but values of 13c of dissolved inorganic c are as low as 60 at shallow depths

isotopic evidence for chemosynthesis based nutrition of macrobenthos the lightness of being at pacific methane seeps the importance of chemosynthetic nutritional pathways was examined for macrofaunal invertebrates 300 mm from methane seeps in the gulf of alaska 4 413 4 443 m on the oregon margin 590 m and on the northern california slope eel river margin 520 m by use of natural abundance stable isotopic data seep macrofauna exhibited lighter d 13 c and d 15 n values than those in nonseep sediments but isotopic signatures varied among seep sites macrofaunal isotopic signatures indicated chemosynthetically fixed carbon sources with a significant contribution from methane derived carbon mdc in macrofauna from sediments of pogonophoran fields averaged 13

late miocene seep carbonates and fluid migration on top of the montepetra intrabasinal high northern apennines italy relations with synsedimentary folding abstract during the miocene hydrocarbon seep carbonates located atop intrabasinal highs and associated with sediment instability formed commonly at the deformation front of the northern apennine collisional orogen the parallelism between the structural trend and the distribution of seep carbonates suggests a close relationship between tectonics and gas fluid emission the montepetra intrabasinal high was formed during the closure stage of the foredeep being related to the synsedimentary growth of an anticline field geometry suggests that detachment folding was the leading mechanism of anticline growth and synsedimentary instability along the anticline flanks ten different bodies of seep carbonates occur in the tortonian early messinian sediments nine in the hinge zone and one in the southern backlimb of the anticline foraminiferal study geochemistry facies investigation and the three dimensional geometry of carbonate bodies with respect to the encasing terrigenous sediments indicate a protracted late tortonian early messinian activity of fluid migration with re mobilization and ascent of sediments from the core of the anticline stabilization of chemosynthesis related communities and in situ brecciation seepage atop the intrabasinal high was fed by different circuits one related to the compaction dewatering of shallow tortonian early messinian sediments and a deeper one related to the deformation of the anticline core and to the activity of detachment surfaces and of faults propagating through the sedimentary cover

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

temporal variability in living deep sea benthic foraminifera a review the deep ocean environment is disturbed by various processes many of which involve episodic inputs of organic matter some inputs e g phytodetritus at mid high latitudes in the north atlantic and northeast pacific are seasonally pulsed others e g falls of whale carcasses are irregular and unpredictable but together they evoke a variety of responses from the benthic biota in the case of deep sea foraminifera only those responses arising from seasonal food pulses have been fairly well documented the population dynamics of deep sea benthic foraminifera total live populations and individual species appear to be controlled largely by two inversely related parameters the flux of organic matter to the seafloor and concentrations of oxygen in the sediment porewater organic matter food inputs are most intense along bathyal continental margins and their oxidation often leads to the depletion of oxygen in surface sediments under these conditions foraminiferal faunas are dominated by low oxygen tolerant infaunal species the abundance of which fluctuate in response to seasonally varying amounts of food and oxygen at some sites e g sagami bay off japan species migrate up and down in the sediments tracking critical oxygen concentrations where oxygen concentrations are consistently low less than about 0 5 ml l 1 as in parts of the california borderland foraminifera may undergo population increases solely in response to food pulses in the abyssal north atlantic and in some continental margin areas of this ocean organic matter inputs are weaker and do not lead to oxygen depletion within surface sediments these systems are food limited and seasonal population fluctuations reflect the availability of food phytodetritus rather than oxygen here the species which respond to phytodetritus are mainly epifaunal or shallow infaunal opportunists which represent a small proportion of highly diverse communities 2 or 3 out of 120 species per core of 25 5 cm2 surface area seasonal phytodetrital pulses to the deep seafloor and hence foraminiferal population dynamics are not entirely predictable being dependent on climatic and upper ocean processes they vary in intensity from year to year and occasionally e g at the porcupine abyssal plain pap in 1997 fail to materialise foraminiferal responses to irregular non seasonal organic matter inputs are poorly known however there is some evidence that whale falls turbidite deposits hydrothermal vents and seeps are exploited by species typical of organically enriched low oxygen environments rather than by a specialised fauna fossil foraminiferal assemblages from bathyal and abyssal environments may provide evidence for an increase or decrease in the seasonality of surface production as well as for longer term changes in palaeoproductivity however the accurate interpretation of this record depends on filling the many gaps which remain in our understanding of relations between benthic foraminiferal ecology and seasonal phenomena in the deep ocean

effects of carbon dioxide sequestration on california margin deep sea foraminiferal assemblages abstract deep sea sequestration of co2 is being considered as a possible mitigation tool to decrease atmospheric co2 concentrations and its associated negative effects this study investigated potential effects of liquid carbon dioxide co2 injection on deep sea foraminiferal assemblages foraminifera are ideal for this ecological impact investigation because of differing test composition calcareous and non calcareous and thickness and diverse epifaunal and infaunal depth preferences the experiment was conducted on august september 2003 at 3600 m off the coast of monterey bay california aboard the r v western flyer using the rov tiburon the ph of the site was monitored throughout the experiment sediment push cores were collected both from the experimental and control sites and stained to distinguish live stained from dead unstained individuals effects of co2 injection on assemblages have been tracked both vertically to 10 cm depth below sea floor and horizontally up to 10 m from co2 injection sites as well as between live and dead individuals within corrals containing the injected co2 and their underlying sediments severe ph changes near 4 0 units were recorded this compares with a record of small average reductions in ocean ph 0 05 units combined with large episodic excursions 1 7 units over the experimental area due to the injection of co2 exposure to this gradient of low ph caused increased mortality and dissolution of calcareous forms within corrals as far as 5 m from the injection site and to at least 10 cm depth in the sediments this experiment revealed several major effects of co2 injection on foraminiferal assemblages in surficial sediments 1 total number of foraminifera in a sample decreases 2 foraminiferal species richness decreases in both stained and unstained specimens and 3 relative percentage of stained live forms in the remaining tests increases down core trends to 10 cm below sea floor have revealed 1 percent agglutinated forms decline and calcareous forms increase with depth 2 agglutinated species richness decreases with depth and 3 experimental core assemblages become increasingly similar with depth to those in control cores not subjected to co2 injection these results imply almost complete initial mortality and dissolution in the upper 10 cm throughout the corrals following liquid co2 injection since calcareous foraminifera represent more than 50 of the total assemblages this clearly indicates that emplacement of co2 will result in negative effects to diversity and survivorship of the deep sea benthic meiofauna

tracing seafloor methane emissions with benthic foraminifera results from the ana submarine landslide eivissa channel western mediterranean sea article the hypothesis that benthic foraminifera are useful proxies of local methane emissions from the seafloor has been verified on sediment core ks16 from the headwall of the ana submarine landslide in the eivissa channel western mediterranean sea the core ms312 from a nearby location with no known methane emis sions is utilised as control the core was analysed for biostratigraphy benthic foraminiferal assemblages hyalinea balthica and uvigerina peregrina carbon and oxygen stable isotope composition and sedimentary structures the upper part of the core records post landslide deglacial and holocene normal marine hemipe lagic sediments with highly abundant benthic foraminifera species that are typical of outer neritic to upper bathyal environment in this interval the 13 c composition of benthic foraminifera indicates normal marine environment analogous to those found in the control core below the sedimentary hiatus caused by the em placement of the slide the foraminiferal assemblages are characterised by lower density and higher shannon index markedly negative 13 c shifts in benthic foraminifera are attributed to the release of methane through the seabed the mean values of the 13 c anomaly in u peregrina are 0 951 0 208 in the pre landslide sediments and 0 269 0 152 in post slide reworked sediments deposited immediately above the hiatus the 13

massive dissociation of gas hydrate during a jurassic oceanic anoxic event in the jurassic period the early toarcian oceanic anoxic event about 183 million years ago is associated with exceptionally high rates of organic carbon burial high palaeotemperatures and significant mass extinction heavy carbon isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon which is isotopically light in contrast examples of light carbon isotope values from marine organic matter of early toarcian age have been explained principally in terms of localized upwelling of bottom water enriched in 12c versus 13c refs 1 2 5 6 here however we report carbon isotope analyses of fossil wood which demonstrate that isotopically light carbon dominated all the upper oceanic biospheric and atmospheric carbon reservoirs and that this occurred despite the enhanced burial of organic carbon we propose that as has been suggested for the late palaeocene thermal maximum some 55 million years ago the observed patterns were produced by voluminous and extremely rapid release of methane from gas hydrate contained in marine continental margin sediments

an apparent polar wander path from the tarim block china abstract the apparent polar wander apw path from the tarim block consists of devonian 16 n 165 e a95 4 late carboniferous 41 n 160 e a95 4 permian 61 n 177 e a95 9 early triassic 69 n 183 e a95 11 and jurassic cretaceous 65 n 214 e a95 6 poles on the basis of this apw path we conclude that tarim rode on a plate subducting under the kazakhstan plate between devonian and permian times by the end of the permian subduction had almost finished early triassic poles from tarim siberia north china and south china are discordant indicating post early triassic relative motions among them cretaceous paleomagnetic poles from tarim north china and south china however are consistent suggesting that china has been a coherent tectonic unit since cretaceous time the shape of the apw path from tarim is similar to that of siberia except that tarim s apw path is systematically displaced to the east a 26 clockwise rotation of tarim s apw path about the euler pole 60 n and 14 e reconciles these two apw paths tarim has moved northeastward some 2000 km relative to a fixed siberia since the cretaceous this northeastward motion of tarim with respect to siberia agrees well with the overall cenozoic tectonic style of asia most of southern china has been pushed eastward to give way to the penetrating indian continent east west and northeast trending left lateral strike slip faults north of the tarim block have been documented however the exact amounts of displacement along these faults are not well known using paleomagnetic data from tarim we will also discuss the tectonic evolution of terranes in central asia and the amount of continental shortening in the tibetan plateau

living stained deep sea foraminifera from the sea of marmara a preliminary study abstract in this preliminary study we investigate living stained foraminifera from the sea of marmara we focus on the faunal composition and geochemical signatures trace elements carbon and oxygen stable isotopes in foraminiferal tests at two deep sea sites 329 and 1240 m depth respectively documented by rov observations and sampling both study areas are heterogeneous including bacterial mats and carbonate concretions proximal to cold seeps and consist of dysoxic bottom water o2

reconstructing benthic carbon oxidation rates using δ13c of benthic foraminifers abstract in non bioturbated organic rich marine sediments the concentration and carbon isotope gradient of total dissolved carbon dioxide co2 primarily reflects the rate of carbon oxidation and co2 diffusion within the sediment pore waters here we investigate whether the calcium carbonate secreted by benthic foraminifers that inhabit discrete depths within the sediments record the pore water 13c co2 gradient and hence can be used as proxies to reconstruct a history of carbon oxidation change the distribution and live abundance of bolivina argentea s l bolivina subadvena s l and buliminella tenuata inhabiting the dysoxic marine sediments along the california margin is similar among sites that differ in co2 gradient by up to a factor of three bolivina argentea inhabits the sediments at the sediment water interface whereas b subadvena s l is most abundant at depths of between 2 and 4 mm buliminella tenuata is most abundant at deeper depths of between 4 and 6 mm the 13c of calcite precipitated by these species matches the 13c of the pore water co2 at the depth of their maximum live abundance indicating that each species has a preferred depth for calcification the 13c difference between the species increases as the rate of carbon oxidation increases these results indicate the carbon isotopic difference between these species in fossil assemblages can be used to estimate changes in the rate of carbon oxidation

biogenetic control of gases in marine sediments of santa barbara basin california abstract the primary controls on the quantity of methane found in sediments are the rates of production and the rates of diffusion in santa barbara basin sediments the diffusion rate of methane is found to be very slow compared to the rate of bacterial production the production rate correlates with the amount of organic matter in the sediment thus the quantity of methane at any depth in the sediment is a function of the amount of marine organic matter initially trapped in the sediment sediment cores show the concentration of so4 decreasing from 27 6 mm at the surface to zero below 2 m the methane concentration is 3 decreases from 1 5 10 4 mmol cu cm year at the surface to less than 10 7 mmol cu cm year at 9 m the production rate of hco3 fluctuates in direct correlation with organic carbon content methane production decreases in a similar manner the dgr13c distribution of biogenic methane variesfrom 92 8 to 23 6 ppt heavy biogenic methane occurs in the upper sulfate reducing zone and may result from the preferential anaerobic oxidation of light methane by sulfate reducin bacteria the diffusive flux of methane into the sulfate reducing zone is between 8 6 10 5 mmol sq end page 919 cm year and 1 75 10 7 mmol sq cm year the diffusion coefficient in this zone is in the range of 2 8 10 7 to 4 2 10 7 sq cm sec below 4 m the diffusion coefficient was less than 5 4 10 8 sq cm sec end of article last page 920

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

stable oxygen and carbon isotopes of live benthic foraminifera from the bay of biscay microhabitat impact and seasonal variability we determined the stable oxygen and carbon isotopic composition of live rose bengal stained benthic foraminifera n150 am size fraction of seven taxa sampled along a downslope transect between 140 to 2000 m water depth in the bay of biscay at the five stations hoeglundina elegans cibicidoides pachydermus uvigerina peregrina uvigerina mediterranea preferentially occupy shallow infaunal niches whereas melonis barleeanus and uvigerina elongatastriata occupy an intermediate infaunal microhabitat and globobulimina spp live in a deep infaunal niche close to the zero oxygen boundary when compared with d 18 o values of calcite formed in equilibrium with bottom waters u peregrina forms its test in close equilibrium with bottom water d 18 o all other foraminiferal taxa calcify with a constant offset to calculated equilibrium calcite there is no systematic relationship between the foraminiferal microhabitat depth and the dd 18 o between foraminiferal and equilibrium calcite we calculated correcting factors for the various taxa which are needed for constructing multispecies based oxygen isotope records in paleoceanographic studies of the study area the d 13 c values of foraminiferal taxa investigated in this study do neither record bottom water d 13 cdic in a 1 1 relationship nor with a constant offset but appear to be mainly controlled by microhabitat effects the increase of d 13 c values of shallow infaunal taxa with increasing water depth reflects the decrease of the exported flux of organic carbon along the bathymetric transect and early diagenetic processes in the surface sediment this is particularly the case for the shallow infaunal u peregrina the d 13 c values of deep infaunal globobulimina spp are much less dependent on the exported organic matter flux we suggest that the dd 13 c between u peregrina and globobulimina spp can shed light on the various pathways of past degradation of organic detritus in the benthic environments at a station in 550 m water depth where periodic eutrophication of sediment surface niches was demonstrated previously we performed a two year seasonal survey of the isotopic composition of foraminiferal faunas no marked seasonal changes of the stable carbon isotopic composition of shallow intermediate and deep infaunal foraminiferal taxa were observed thus the d 13 c values of foraminiferal individuals belonging to the n150 am fraction may result from rather long term calcification processes lasting for several weeks or months which limit the impact of ephemeral 12 c enrichment of shallow infaunal niches on the isotope chemistry of adult individuals during eutrophic periods only highly opportunistic taxa reproducing or calcifying during

terrestrial record of methane hydrate dissociation in the early cretaceous reconstruction of changing c isotopic composition of early cretaceous atmospheric co2 from fossilized c3 vascular land plant tissue revealed a brief and striking negative excursion d 25 in atmospheric d 13 c followed by a rapid positive compensation d 15 during the aptian ca 117 ma mass balance calculations show that dissociation of a small amount of methane gas hydrate is the most tenable cause of the negative excursion this would also result in an increased co2 o2 mixing ratio as o2 is consumed during ch4 oxidation to co2 spurring the exponential phase of angiosperm biogeographic expansion

low δ13c in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage 1 to investigate the use of benthic foraminifera as a means to document ancient methane release we determined the stable isotopic composition of tests of live rose bengal stained and dead specimens of epibenthic fontbotia wuellerstorfi preferentially used in paleoceanographic reconstructions and of endobenthic high latitude cassidulina neoteretis and cassidulina reniforme from a cold methane venting seep off northern norway we collected foraminiferal tests from three push cores and nine multiple cores obtained with a remotely operated vehicle and a video guided multiple corer respectively all sampled sites except one control site are situated at the hakon mosby mud volcano hmmv on the barents sea continental slope in 1250 m water depth at the hmmv in areas densely populated by pogonophoran tube worms 13c values of cytoplasm containing epibenthic f wuellerstorfi are by up to 4 4 lower than at control site thus representing the lowest values hitherto reported for this species live c neoteretis and c reniforme reach 13c values of 7 5 and 5 5 vienna pee dee belemnite vpdb respectively whereas 13c values of their empty tests are higher by 4 and 3 however 13c values of empty tests are never lower than those of stained specimens although they are still lower than empty tests from the control site this indicates that authigenic calcite precipitates at or below the sediment surface are not significantly influencing the stable isotopic composition of foraminiferal shells the comparatively high 13c results rather from upward convection of pore water and fluid mud during active methane venting phases at these sites these processes mingle tests just recently calcified with older ones secreted at intermittent times of less or no methane discharge since cytoplasm containing specimens of suspension feeder f wuellerstorfi are almost exclusively found attached to pogonophores which protrude up to 3 cm above the sediment and 13c values of bottom water dissolved inorganic carbon dic are not significantly depleted we conclude that low test 13c values of f wuellerstorfi are the result of incorporation of heavily 13c depleted methanotrophic biomass that these specimens feed on rather than because of low bottom water 13cdic alternatively the pogonophores which are rooted at depth in the upper sediment column may serve as a conduit for depleted 13cdic that ultimately influences the calcification process of f wuellerstorfi attached to the pogonophoran tube well above the sediment water interface the lowest 13c of live specimens of the endobenthic c neoteretis and c reniforme are within the range of pore water 13cdic values which exceed those that could be due to organic matter decomposition and thus in fact document active methane release in the sediment

chemical and isotopic evidence of gas influenced flow at a transform plate boundary monterey bay california chemical and isotopic compositions of pore fluids document upward flow through communities of vesicomyid clams in monterey bay california within the clam communities the sulfate reduction zone is only 10 cm thick and ca and mg concentrations decrease to values as low as 2 2 mm and 34 5 mm respectively at depths less than 30 cm below the sediment water interface less than 5 m outside the communities the base of the sulfate reduction zone is deeper than the greatest penetration of the cores 30 cm and ca and mg exhibit only minor changes from seawater values the sediment exhibits no significant variation in grain size mineralogy organic carbon nitrogen or carbonate content throughout the region the composition of pore fluid within clam communities results from upward flow of altered fluid rather than different diagenetic reactions within and outside the communities isotopically light dissolved inorganic carbon dic with 13c values ranging from 3 2 to 54 1 could reflect carbon sources from either oxidized thermogenic methane and or a mixture of oxidized microbial methane and solid organic carbon the c1 c2 c3 ratios ranging from 34 to 1142 and the hydrogen and carbon isotopic compositions of methane d values of 109 to 156 13c values of 30 6 to 86 6 suggest that methane is primarily microbial but that a minor component could be thermally generated any thermogenic methane would have migrated from great depths possibly 2 km the presence of methane is likely to contribute to fluid flow by reducing the density of the fluids past fluid migration and venting are reflected by widespread carbonate mineralization at the sediment water interface this mineralization and the geographic distribution and proportions of microbial and thermogenic methane suggest that vent sites migrate when permeability is reduced during carbonate cementation these results demonstrate that along with convergent and divergent plate boundaries transform plate boundaries are characterized by fluid flow and that the flow may be widespread occurring at sites away from fault zones

carbon and oxygen isotope geochemistry of live stained benthic foraminifera from the aleutian margin and the southern australian margin article comparisons of ambient bottom water geochemistry and stable isotopic values of the tests of living stained calcareous benthic foraminifera from the north pacific on the aleutian margin water depth 1988 m and murray canyons group in the southern indian ocean australian margin water depths 2476 m and 1634 m provide modern environmental analogs to calibrate paleoenvironmental assessments consistent with the hypothesis that microhabitat preferences influence foraminiferal isotopic values benthic foraminifera from both margins were depleted in 13 c with respect to bottom water dissolved inorganic carbon dic the carbon isotope values of deep infaunal foraminifera chilostomella oolina globobulimina pacifica showed greater differences from estimates of those of dic than shallow benthic foraminifera bulimina mexicana bolivinita quadrilatera pullenia bulloides this study provides new isotopic and ecological information for b quadrilatera the mean 13 c value defined as foraminiferal 13 c values minus estimated ambient 13 c values from the aleutian margin is 0 97 higher for g pacifica than the mean from the murray canyon this difference may result either from genetic or biological differences between the populations or from differences in environmental isotopic influences such as pore water differences that were not accounted for in the equilibrium calculations these analyses provide calibration information for the evaluation of bottom water conditions and circulation patterns of ancient oceans based on fossil foraminiferal geochemistry

deep sea habitat heterogeneity influence on meiofaunal communities in the gulf of guinea to estimate the degree of spatial heterogeneity of benthic deep sea communities we carried out a multiple scale from m s to 200 km investigation in the congo angola margins equatorial west african margin 3150 4800 m in which we examined the metazoan meiofauna at a variety of habitats along the congo channel system and in the associated cold seep we investigate the structure density vertical distribution patterns in the sediment and biomass of meiofaunal communities in the gulf of guinea and how they are controlled by hydrologic and biogeochemical processes the meiofaunal communities in the gulf of guinea were shaped by heterogeneous conditions on the margin and reflect the multiple scale spatial variability that corresponds with the different identified habitats the two control sites located at 100 km away from the canyon were inhabited by very dense and the most diverse meiobenthic communities similar meiobenthic communities inhabited the transition zone between the canyon and the cold seep sites located along the congo channel were obviously affected by the local high velocity bottom currents and unstable sedimentary conditions in this active submarine system extremely low meiobenthic densities and very low proportions in the most surficial sediment layers provided evidence for recently highly disturbed sediments at these sites the remote operated vehicle rov victor 6000 provided images of the cold seep showing a patchy distribution of several types of patchy distributed megafaunal communities dominated by three key symbiotic taxa mytilidae vesicomyidae and siboglinidae these cold seep sediments were colonised by a unique meiobenthic community characterised by a high small scale m s patchiness low species richness and the prominent dominance of two large sized nematode species sabatieria mortenseni which is a cosmopolitan nematode known from littoral habitats and an undescribed desmodora species the high individual body weight of s mortenseni and its dominance at the cold seep site resulted in a significantly higher nematode biomass at the seep compared to the surrounding sites in addition the vertical nematode profiles with maximum proportions in subsurficial layers points to a chemosynthesis based meiobenthic community in this cold seep in contrast to the phytodetritus based communities at the control sites and at the transition zone

initial mapping of mercury s crustal magnetic field relationship to the caloris impact basin seventy eight low altitude passes of mercury surface space environment geochemistry and ranging magnetometer data from august to september of 2014 have been applied to produce an approximate map of the crustal magnetic field at a constant altitude of 80 km covering latitudes of 50 80 n and longitudes of 160 330 e the strongest anomalies are located in the westernmost part of the mapped region just north and northeast of the caloris impact basin the strongest single anomaly group lies over a smooth plains unit that extends northward from caloris a second anomaly lies on the odin formation interpreted as primary caloris ejecta a third broad anomaly also lies over a smooth plains unit suisei planitia although many smooth plains on mercury may have a volcanic origin a subset of these plains is concentrated around caloris and could have a dominantly impact origin it is therefore proposed that many of the mercurian anomaly sources consist of impact basin ejecta materials

submillimeter life positions of bacteria protists and metazoans in laminated sediments of the santa barbara basin to provide insights into the biogeochemistry of environments where steep chemical gradients place anaerobes microaerophiles and aerobes in close proximity it might be necessary to survey biotic distributions on scales that are not possible using conventional ecological approaches to overcome such limitations we adapted sedimentological and cell biological methods to examine the life positions of microbes within sediments this fluorescently labeled embedded core flec technique was used to survey the submillimeter distributions of eukaryotic nanobiota and meiofauna plus co occurring prokaryotes inhabiting laminated sediments of the bathyal santa barbara basin sbb 34 13 n 120 02 w although sbb sediments were vertically structured on the scale of millimeters i e as laminae and microelectrode profiles suggested vertically distinct oxygenated and anoxic sulfidic layers the distributions of aerobes microaerophiles and sulfide tolerant anaerobes were not concomitantly structured unprecedented associations were observed among microorganisms for example relatively deep in the sediments where high sulfide concentrations were expected flagellates were intimately associated with beggiatoa ciliates were typically solitary whereas flagellates were often aggregated in nearly monomorphotypic swarms of 3 104 mm 3 such aggregations could significantly affect geochemical pore water processes at scales 1 l our observations indicate that a mosaic of chemically heterogeneous microhabitats exist in both vertical and horizontal dimensions suggesting that biogeochemical processes in the sbb are more complex than predictions based on standard biotic assessments and microelectrode profiling

late holocene foraminifera of blake ridge diapir assemblage variation and stable isotope record in gas hydrate bearing sediments abstract the presence of gas hydrates on the blake ridge diapir northeastern atlantic ocean offers an opportunity to study the impact of methane seepage on the ecology and geochemistry of benthic foraminifera in the late holocene three push cores covering a time span of 1000 yrs were retrieved from three distinct microhabitats at the top of the diapir at a water depth of 2150 m i sediments away from seepage control core ii sediments overlain by clusters of methanotrophic and thiotrophic bivalves and iii chemoautotrophic microbial mats the foraminiferal assemblages at the two seep sites are marked by a reduction in benthic foraminiferal species diversity coupled with a near absence of agglutinated species however an opportunistic population rise in ch4 or h2s tolerant calcareous species e g globocassidulina subglobosa and cassidulina laevigata that utilize the abundant trophic resources at the seeps has led to an increase in the overall assemblage density there the 18o and 13c values of three species of benthic foraminifera gyroidinoides laevigatus globocassidulina subglobosa and uvigerina peregrina and the planktonic species globorotalia menardii were acquired from all three cores the benthic species from methane seeps yield 13c values of 0 1 to 4 2 vpdb that are distinctly more 13c depleted relative to the 13c of 0 4 to 1 0 vpdb at the control off seep site the species from a mussel bed site exhibit more negative 13c values than those from microbial mats possibly reflecting different food sources and higher rate of anaerobic oxidation of methane the positive 13c values in the paired planktonic species suggest that authigenic carbonate precipitation did not overprint the observed 13c depletions hence the probable cause of negative 13c of benthic foraminifera is primary calcification from dissolved inorganic carbon dic containing mixed carbon fractions from a highly 13c depleted microbially oxidized methane and b a seawater source

carbon stable isotopic composition of benthic foraminifera from pliocene cold methane seeps cascadia accretionary margin abstract cold methane seep carbonates preserve the distinctive carbon stable isotope signatures of their ambient porewaters thus facilitating the identification of methane sources and fluid migration pathways this study employs an isotopic indicator from microfossils in a diffuse fossil seep for the recognition and characterization of methane seepage in the rock record benthic foraminifera from the pliocene quinault formation western washington state are plentiful and provide a temporal link between modern and more ancient seeps stable carbon isotope analyses of individual foraminiferal tests revealed a clear distinction between seep and non seep foraminifera infaunal species globobulimina pacifica and nonion basispinatum collected from seep samples exhibited 13 c values that were highly variable and often strongly depleted values ranged from 33 1 to 55 3 pdb in g pacifica and from 2 1 to 42 9 pdb in n basispinatum the epifaunal species cibicidoides mckannai though less depleted also showed considerable variability with 13 c values ranging from 1 7 to 3 1 pdb in contrast non seep specimens were much more enriched and less variable non seep specimens of n basispinatum displayed 13 c values clustering between 0 5 and 1 5 pdb while non seep specimens of c mckannai yielded a range of 1 1 to 1 8 pdb sem analyses and oxygen isotope values of foraminiferal tests indicated minimal diagenetic alteration 13 c values from authigenic blebs small nodules with wispy indistinct boundaries ranged from 8 7 to 38 4 pdb by combining these inorganic carbonate data with the foraminiferal values the association of seep specific bivalves and the present day leakage of thermogenic methane from the nearby garfield gas mound we conclude that these foraminifera precipitated their tests in the presence of methane derived carbon thus they record pore water 13 c depletion and syn depositional fluid flow pathways near the sediment water interface in a seep system active 3 4 mya and continuing onshore and offshore today the range and degree of 13 c depletion in the pliocene microfossils is due to the heterogeneity of seepage caused by different methane sources i e thermogenic and biogenic the tortuosity of fluid migration pathways reaching the seafloor sediments and mixing of seep fluids with dissolved inorganic carbon dic and marine organic carbon

new records of oligocene diffuse hydrocarbon seeps northern cascadia margin abstract fossil methane seeps are preserved in late eocene through pliocene marine sedimentary units of the cascadia margin of the northeastern pacific all cascadia fossil seeps are situated in the uplifted accretionary wedge that overlies extensive middle eocene coal bearing units and the paleocene early eocene siletzia large igneous province this study describes eight previously unrecorded oligocene seeps all of which are identified by small scattered carbonates with or without accompanying characteristic seep macrofauna from both inner and outer shelf depths we interpret these deposits as reflecting spatially and temporally diffuse seepage of hydrocarbon enriched fluids sourced from various carbon sources within the actively deforming accretionary prism and term them diffuse seeps 13c and 18o values from foraminiferal carbonate from the studied stratigraphic units have broad variability authigenic carbonates occurring as nodules blebs burrow fill and fracture fill indicated microbial and thermogenic methane and multiple fluid flow pathways from within the actively deforming accretionary wedge it is apparent that the complex fluid flow regime observed in modern seeps of the cascadia margin is a continuation of one established in the late eocene

a time series study of the carbon isotopic composition of deep sea benthic foraminifera 1 variation of the 13c of living rose bengal stained deep sea benthic foraminifera is documented from two deep water sites 2430 and 3010 m from a northwest atlantic ocean study area 275 km south of nantucket island the carbon isotopic data of hoeglundina elegans and uvigerina peregrina from five sets of multicorer and soutar box core samples taken over a 10 month interval march may july and october 1996 and january 1997 are compared with an 11 5 month time series of organic carbon flux to assess the effect of organic carbon flux on the carbon isotopic composition of dominant taxa carbon isotopic data of hoeglundina elegans at 3010 m show 0 3 lower mean values following an organic carbon flux maximum resulting from a spring phytoplankton bloom this 13c change following the spring bloom is suggested to be due to the presence of a phytodetritus layer on the seafloor and the subsequent depletion of 13c in the pore waters within the phytodetritus and overlying the sediment surface carbon isotopic data of h elegans from the 2430 m site show an opposite pattern to that found at 3010 m with a 13c enrichment following the spring bloom this different pattern may be due to spatial variation in phytodetritus deposition and resuspension or to a limited number of specimens recovered from the march 1996 cruise the 13c of uvigerina peregrina at 2430 m shows variation over the 10 month interval but an analysis of variance shows that the variability is more consistent with core and subcore variability than with seasonal changes the isotopic analyses are grouped into 100 m size classes on the basis of length measurements of individual specimens to evaluate 13c ontogenetic changes of each species the data show no consistent patterns between size classes in the 13c of either h elegans or u peregrina these results suggest that variation in organic carbon flux does not preferentially affect particular size classes nor do 13c ontogenetic changes exist within the 250 to 750 m size range for these species at this locality on the basis of the lack of ontogenetic changes a range of sizes of specimens from a sample can be used to reconstruct 13c in paleoceanographic studies the prediction standard deviation which is composed of cruise core subcore and residual replicate variability provides an estimate of the magnitude of variability in fossil 13c data it is 0 27 for h elegans at 3010 m and 0 4 for u peregrina at the 2430 m site since these standard deviations are based on living specimens they should be regarded as minimum estimates of variability for fossil data based on single specimen analyses most paleoceanographic reconstructions are based on the analysis of multiple specimens and as a result the standard error would be expected to be reduced for any particular sample the reduced standard error resulting from the analysis of multiple specimens would result in the seasonal and spatial variability observed in this study having little impact on carbon isotopic records

relationships between the stable isotopic signatures of living and fossil foraminifera in monterey bay california 1 fossil foraminifera are critical to paleoceanographic reconstructions including estimates of past episodes of methane venting these reconstructions rely on benthic foraminifera incorporating and retaining unaltered the ambient isotopic compositions of pore fluids and bottom waters comparisons are made here of isotopic compositions of abundant live and fossil foraminifera uvigerina peregrina epistominella pacifica bulimina mexicana and globobulimina pacifica collected in monterey bay ca from two cold seeps clam flats and extrovert cliffs and from sediments 5 m outside of the clam flats seep clam flats has steep d 13 cdic gradients to 45 but dic at extrovert cliffs is less enriched in 12 c to approximately 22 oxygen isotope values of fossil foraminifera at clam flats are 1 5 enriched in 18 o over the living foraminifera as well as those of both live and fossil foraminifera at extrovert cliffs suggesting they may have lived during the last glacial maximum statistical comparisons student s t and kolmogorov smirnov tests of d 13 c and d 18 o values indicate that live and fossil foraminifera come from different populations at both clam flats and extrovert cliffs at clam flats the difference appears to result from alteration enriching some fossil foraminifera in 12 c over live foraminifera at extrovert cliffs the fossil foraminifera are enriched in 13 c over the live foraminifera suggesting they lived prior to the onset of venting and thus that venting began recently the short time of venting at extrovert cliffs may be responsible for the less alteration there compared with clam flats these results indicate that preservation of foraminifera is likely to be poor within long lived cold seeps but that foraminifera living in the surrounding sediment may incorporate and preserve broad basin wide changes in isotopic compositions of the ambient water

foraminiferal oxygen and carbon isotopes during the last 34 kyr off northern japan northwestern pacific abstract oxygen and carbon isotopes of foraminifera were analyzed in core pc4 water depth 1366 m off northern japan near the east side of the tsugaru strait 130 m depth between the open northwestern pacific ocean and the japan sea at present the site is at the confluence of the tsugaru warm current which flows eastwards out of the sea of japan through the tsugaru strait the subarctic oyashio current and the subtropic kuroshio current during the last glacial maximum lgm the oyashio current penetrated further to the south and outflow from the japan sea was restricted by glacio eustatic sea level lowering the isotopic values of the planktic foraminifer neogloboquadrina pachyderma sinistral and the benthic foraminifer uvigerina akitaensis reflect rapid millennial scale paleoceanographic changes between 34 and 6 ka hydrographic changes during deglaciation were related to events at high northern latitudes but holocene hydrographic changes were dominated by local effects such as the development of the outflow of the tsugaru warm current high values of planktic 18 o during the lgm reflect the southward advance of the oyashio current these values decreased by 0 3 from 19 4 to 18 9 ka then increased by 0 5 at 18 ka with highest values between 17 5 and 15 ka the 18 o oscillations between 19 4 and 15 ka may reflect millennial scale warm cold oscillations during heinrich event 1 planktic microfossil data indicate that cold oyashio waters flowed from the northwestern pacific into the japan sea via the tsugaru strait between 17 and 16 ka consistent with the occurrence of the highest planktic 18 o values in core pc4 planktic 18 o values rapidly decreased by 0 9 at 15 ka possibly reflecting the effects of both a rapid increase in fresh water flux and rising temperatures in the subarctic north pacific during the younger dryas cold event planktic 18 o values increased by 0 5 followed by a gradual decrease by 1 from the early to middle holocene reflecting a gradual increase in eastward outflow via the tsugaru strait with sea level rise both planktic and benthic foraminiferal 13 c values oscillated between 34 and 10 ka at relatively large amplitudes about 0 5 then remained relatively stable during the last 10 kyr several negative planktic and benthic 0 7 13 c excursions were present in sediment dated between the precipitation of secondary carbonates during episodic methane release possibly associated with methane release from continental margin sediments

distribution and isotopic composition of foraminifera at cold seep site 973 4 in the dongsha area northeastern south china sea abstract a 1375 cm long gravity core site 973 4 was acquired from the dongsha cold seep area of the northeastern south china sea scs we measured its stable isotopes of planktonic foraminifera and investigated benthic foraminiferal assemblage compositions accelerator mass spectrometry 14c analysis of planktonic foraminifera shows that some intervals are dated to marine isotope stage mis 3 pulleniatina obliquiloculata has positive 13c 0 25 1 25 except for a negative carbon isotopic excursion up to 13c 1 15 but its light carbon sources remain elusive the benthic 13c values uvigerina of non seep and cold seep boreholes from the scs have no systematic difference therefore the benthic 13c at site 973 4 did not record the enhanced seepage activities if occurred during the last sea level lowstand in the dongsha area in the pre holocene sediments the foraminiferal assemblages have lower diversities shannon wiener indices evenness indices simpson indices and higher calcareous proportions like typical cold seep settings the changes in oxygen levels lower in the glacial period than those in the holocene indicated by foraminiferal indices reflect either bottom water oxygen variations on the glacial interglacial scale or enhanced seepage activities during the last glacial period

combined carbonate carbon isotopic and cellular ultrastructural studies of individual benthic foraminifera 2 toward an understanding of apparent disequilibrium in hydrocarbon seeps 1 numerous previous studies show disequilibrium between stable carbon isotope ratios of foraminiferal calcite and pore water dissolved inorganic carbon in hydrocarbon seeps calling into question the utility of this widely used paleoceanographic tracer as a proxy we use a recently developed method to compare stable carbon isotope ratios of foraminiferal carbonate with cell ultrastructural observations from individual benthic foraminifera from seep under chemosynthetic bivalves and nonseep habitats in monterey bay california to better understand control s of benthic foraminiferal carbon isotope ratios two attributes previously proposed to cause the isotopic offsets are diet and symbionts ultrastructural analysis shows that positive staining with rose bengal indicates presence of foraminiferal cytoplasm bacterial biomass or a combination of both and thus is not an unequivocal indicator of viability we also show for the first time that some living seep foraminifera have endobionts results from our unique yet limited data set are consistent with suggestions that in our sites several foraminiferal species collected from seep clam beds may not survive there diet and symbiont presence do not appear to be major contributors to disequilibrium little calcification of seep tolerant foraminiferal species occurs while seep conditions prevail and microscale variability in habitats could influence 13c of benthic foraminiferal carbonate results further suggest that our knowledge of benthic foraminiferal ecology and biomineralization especially in extreme habitats such as seeps must be bolstered before we fully understand the fidelity of paleoenvironmental records derived from benthic foraminiferal test 13c data