contemporaneous early diagenetic formation of organic and inorganic sulfur in estuarine sediments from st andrew bay florida usa estuarine sediment samples were collected from nine stations in st andrew bay near panama city florida usa contrasting grain size and varying concentration of organic carbon allowed a comparative study of the relationships among organic degradation processes sulfur cycling and diagenetic removal of dissolved sulfide produced by bacterial sulfate reduction abundance and sulfur isotopic composition were determined for dissolved sulfide dissolved sulfate pyrite humic acid sulfur fulvic acid sulfur and elemental sulfur presence of free dissolved sulfide and enrichment in 34s of porewater sulfate in samples from organic rich muddy sediments of st andrew bay indicate high rates of sulfate reduction and anoxic conditions below 5 mm depth such conditions are not reflected in samples from organic poor sandy near shore sediments collected from highly productive areas occupied by seagrass beds in this estuarine system pyrite and fulvic acid sulfur are the largest sinks for sulfide produced by bacterial sulfate reduction strong correlation between abundances of pyrite and fulvic acid sulfur suggests coincident formation in the uppermost 10 cm of sediment large differences in isotopic composition between these two species and consistent enrichment in 34s of the fulvic acid fraction however indicate two different reaction pathways abundance and sulfur isotopic composition of humic acid and fulvic acid sulfur suggest that organic sulfur is derived from mixing between 1 34s depleted sulfur with an unknown oxidation state that was recycled from bacterial hydrogen sulfide and 2 34s enriched sulfur interpreted as primary biosynthetic sulfur originally assimilated from dissolved sulfate samples taken from sandy sediment localities where aquatic vascular plants are rooted in the anoxic zone show a strong depletion in 34s in the fulvic acid sulfur fraction suggesting recycled hydrogen sulfide as the dominant source of organic sulfur

late pleistocene to holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments southwestern taiwan abstract a core drilled at san liao wan in the southwestern coastal plain of taiwan has been analyzed for total sulfur contents isotopic values as well as ratios of pyritic sulfur to organic carbon our results demonstrate a close relationship between late pleistocene sea level change and the proxies generated in this study the inorganic sulfur contents indicate that at our study site the holocene transgression started at 11 ka and remained under seawater for thousands of years until the late holocene corresponding to a depth of 20 m in the study core the uppermost 20 m of core shows relatively high total organic carbon toc and 34s of inorganic sulfur suggesting a transitional environment such as muddy lagoon or marsh before the site turned into a modern coastal plain in the lower part of the core at depths of 110 145 m corresponding ages of 12 30 ka low sulfur contents are recorded probably indicating fluvial sediments deposited during the oceanic isotope stage ois 2 a sea level lowstand the lower part of the core roughly within ois 3 records at least two transgressions although the transgressional signals may be somewhat obscured by subsequent weathering the reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data however the marine organic source was periodically dominant the modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments probably indicating that the sulfate migrated into the site subsequent to early diagenesis

bulk kinetic parameters and structural moieties of asphaltenes and kerogens from a sulphur rich source rock sequence and related petroleums non isothermal open system pyrolysis gas chromatography and bulk petroleum generation experiments were performed on type ii s petroleum asphaltenes source rock asphaltenes and related kerogens to evaluate petroleum composition and generation timing the results show that contrary to convention there are significant differences in the reactivity between petroleum asphaltenes and their related kerogens in the studied type ii s petroleum system and these samples yield kinetic models that predict onset peak and completion of petroleum generation under different temperatures petroleum asphaltenes and source rock asphaltenes are less stable and show tighter petroleum formation windows than kerogens when extrapolated to geological heating rates source rock asphaltene related kerogen and oil asphaltene pyrolysates possess structural differences as revealed in the aromaticity and organic sulphur content aromaticity was highest in pyrolysates of source rock asphaltenes intermediate in kerogen pyrolysates and lowest in pyrolysates from petroleum asphaltenes in addition the highest organic sulphur content was identified in kerogen pyrolysates whereas pyrolysates of both source rock and petroleum asphaltenes are similar in organic sulphur content thus the amount of organic sulphur is not proportional to the reactivity of petroleum generation from asphaltenes at lower thermal stress it is more likely that kerogens and asphaltenes possess different configurations and types of sulphur bonds resulting in cracking of covalent bonds at different levels of thermal stress

sulfur enrichment of humic substances in a delaware salt marsh sediment core abstract humic sulfur operationally defined as the sulfur extracted with humic substances in 0 l n naoh solution comprises up to 51 of the total sulfur inventory in a sediment core taken from a delaware spartina alterniflora marsh pyrite sulfur is the next largest fraction except at the near surface sediments where zerovalent sulfur concentrations are significant x ray photoelectron spectroscopy indicates that the humic sulfur consists of sulfoxides or sulfones and in a more reduced state organic sulfides and or organic polysulfides a subsurface decrease in the humic acid c s atomic ratio to 56 2 suggests that the upper 4 cm of marsh sediment is the locus for humic sulfur formation s alterniflora detritus and microbial biomass cannot fully account for observed sulfur enrichment of humic c s atomic ratios therefore the enrichment of humic substances by sulfur is probably via reaction of reduced sulfur compounds with organic matter a humic sulfur formation rate of 10 6 mol s cm 3 a 1 is calculated for the surface sediments and leads to an areal production of 18 mol s cm 2 a 1 of humic sulfur humic sulfur formation and preservation is enhanced by the limited availability of iron for the rapid precipitation of iron sulfide minerals and the apparent resistance of organic sulfur compounds towards reoxidation to sulfate especially in the upper 9 cm of marsh sediment where inorganic sulfur compounds are rapidly oxidized

geochemistry of inorganic and organic sulphur in organic rich sediments from the peru margin abstract we have determined 1 the abundance and isotopic composition of pyrite monosulphide elemental sulphur organically bound sulphur and dissolved sulphide 2 the partition of ferric and ferrous iron 3 the organic carbon contents of sediments recovered at two sites drilled on the peru margin during leg 112 of the ocean drilling program sediments at both sites are characterised by high levels of organically bound sulphur obs obs comprises up to 50 of total sedimentary sulphur and up to 1 of bulk sediment the weight ratio of s to c in organic matter varies from 0 03 to 0 15 mean 0 10 such ratios are like those measured in lithologically similar but more deeply buried petroleum source rocks of the monterey and sisquoc formations in california the sulphur content of organic matter is not limited by the availability of porewater sulphide isotopic data suggest that sulphur is incorporated into organic matter within a metre of the sediment surface at least partly by reaction with polysulphides most inorganic sulphur occurs as pyrite pyrite formation occurred within surface sediments and was limited by the availability of reactive iron but despite highly reducing sulphidic conditions only 35 65 of the total iron was converted to sulphide 10 30 of the total iron still occurs as fe iii in surface sediments the isotopic composition of pyrite is similar to that of both iron monosulphide and dissolved sulphide either pyrite like monosulphide formed by direct reaction between dissolved sulphide and detrital iron and or the sulphur species responsible for converting fes to fes2 is isotopically similar to dissolved sulphide likely stoichiometries for the reaction between ferric iron and excess sulphide imply a maximum resulting fes2 fes ratio of 1 1 where pyrite dominates the pool of iron sulphides at least some pyrite must have formed by reaction between monosulphide and elemental sulphur and or polysulphide elemental sulphur s0 is most abundant in surface sediments and probably formed by oxidation of sulphide diffusing across the sediment water interface in surface sediments s0 is isotopically heavier than dissolved sulphide fes and fes2 and is unlikely to have been involved in the conversion of fes to fes2 polysulphides are thus implicated as the link between fes and fes2

a jurassic counterpart for modern kopara of the pacific atolls abstract two types of laminated sediments are compared in this paper the kimmeridgian bituminous laminites of orbagnoux french southern jura mountains and the present day kopara of the french polynesia atolls or kiritimati christmas island from the pacific ocean the kopara is made of laminated sediments several tens of centimetres thick that cover the floors of most shallow 3 rich laminae the top few centimetres host a succession of bacterial populations from aerobic to strictly anoxic most carbonate grains are precipitated in situ due to bacterial activity s l the kimmeridgian bituminous laminae of orbagnoux are partly made of flat stromatolites that show many similarities with the kopara this analogy allows us to refine the interpretation of the southern jura platform where laminated organic matter rich carbonates were deposited in many places

evidence for a composite organic inorganic fabric of belemnite rostra implications for palaeoceanography and palaeoecology carbonate skeletons of fossil marine organisms are widely used to reconstruct palaeoceanographic parameters specifically the geochemistry of jurassic and cretaceous belemnite rostra is traditionally interpreted to represent near sea surface seawater properties more recently an increasing number of workers have reported significant scatter in geochemical data e g 18o 13c element ca ratio when comparing rostra from the same stratigraphic level or within a single belemnite rostrum this scatter is not explained by differential diagenetic overprint alone here we report petrographic evidence on the primary ultrastructure of rostra of megateuthis middle jurassic and belemnitella and gonioteuthis late cretaceous the biogenic ultrastructure consists of a filigree framework of triaxial branches and tetrahedrons of variable size forming a honeycomb like network data presented here suggest that these rostra yielded as much as 50 to 90 primary pore space on the level of a working hypothesis and in analogy with modern cephalopods we propose that the pore space was formerly filled with body fluid and or organic compounds during the life time of these organisms intra rostral porosity was post mortem occluded by earliest diagenetic isopachous calcite cements of a non biogenic origin these may have been precipitated due to increased alkalinity related to the decay of organic matter if this holds true then the resulting fabric represents a composite biogenic abiogenic structure in order to optically separate the two calcite phases forming a single calcite fibre we employed a wide range of state of the art analytical tools to thin sections and ultra thin sections of well preserved specimens pending a verification of these well supported ultrastructural data by means of high resolution geochemical analyses from biogenic and abiogenic phases we suggest that these findings have significance for those using belemnite rostra as archives of their palaeoenvironment

the key role of diabatic outflow in amplifying the midlatitude flow a representative case study of weather systems surrounding western north pacific extratropical transition abstractrecurving tropical cyclones tcs undergoing extratropical transition et may substantially modify the large scale midlatitude flow pattern this study highlights the role of diabatic outflow in midlatitude flow amplification within the context of a review of the physical and dynamical processes involved in et composite fields of 12 western north pacific et cases are used as initial and boundary conditions for high resolution numerical simulations of the north pacific north american sector with and without the tc present it is demonstrated that a three stage sequence of diabatic outflow associated with different weather systems is involved in triggering a highly amplified midlatitude flow pattern 1 preconditioning by a predecessor rain event pre 2 tc extratropical flow interaction and 3 downstream flow amplification by a downstream warm conveyor belt wcb an ensemble of perturbed simulations demonstrates the robustness of these stages beyond earlier studies investigating pres recurv

sulfur storage and alkalinity generation in new england lake sediments we measured rates of burial and forms of reduced s in lake sediments to evaluate the importance of so z reduction to the alkalinity budget of several new england lakes the contribution of dissimilatory sod2 reduction to alkalinity generation in these lakes was estimated conservatively to range from 1 to 75 meq m 2 yr l the contribution of both assimilatory and dissimilatory sod2reduction ranged from 10 to 159 meq m 2 yr l for lakes with water residence times on the order of years sod2 reduction can be important in controlling lake water alkalinity we found substantial quantities of inorganic reduced s in sediments of nearly all of the lakes that we studied the majority was present as pyrite in most lakes concentrations of inorganic reduced s were higher in sediments deposited in the last 85 yr when compared to older sediments in contrast the ratio of c to organic s showed no consistent trend with depth in most lakes it appears that in these lakes most of the sulfide produced from s0 2 reduction is stored primarily as inorganic forms rather than as c bonded s in lakes with highly organic sediments and low fe concentrations we found that a considerable portion of the sedimentary fe was present as ferrous sulfides if these lakes were typical alkalinity generation bv reduced s storage in lakes with organic rich sediments in the northeastern u s ilready may be limited by fe availability

abrupt vegetation change after the late quaternary megafaunal extinction in southeastern australia the extinction of megafauna in australia about 43 000 years ago has been linked to both human arrival and vegetation change marine sediment analyses from the east coast of australia suggest that vegetation change was a result rather than cause of the extinction

diagenetic pyritisation under eastern mediterranean sapropels caused by downward sulphide diffusion recurrent organic rich layers sapropels in eastern mediterranean sediments are enriched in corg fe and s sulphur and fe are enriched in a zone immediately below the sapropels whereas corg is not 34s values of bulk sediments and simple mass balance calculations indicate that so42 reduction has taken place in an open system with all hs formed at or close to the sediment surface formation of pyrite in the sapropel was fe limited and consequently excess hs was able to migrate downwards downward sulphidisation this resulted in the formation of pyrite below the sapropel by reaction of this hs with solid phase ferric iron and fe2 diffusing upwards from underlying sediments the fe2 source probably includes fe hydr oxide layers formed at former oxidation fronts above previously deposited and buried sapropels this downward sulphidisation mechanism allows accumulation of twice as much s in alternating organic rich anoxic organic poor suboxic sediments compared to what is preserved in organic rich anoxic sediments

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

phytane from chemolytic analysis of modern marine sediments a product of desulfurization or not a set of modern marine sediments was analyzed to evaluate the role of sulfurization as a mechanism for biomarker preservation during early diagenesis the set consisted of sediments accumulating within various oxic to anoxic depositional environments raney nickel treatment of the polar fraction of total extractable lipids ptel from each sample yielded 3 7 11 15 tetramethylhexadecane phytane as the dominant product accompanied in several cases by minor levels of c27 c28 and c29 5 h steranes n c31 alkane and carotane although others have ascribed such products to a desulfurization reaction our work reveals significant production of phytane from the action of raney nickel on the esterified side chain of chlorophyll results suggest that catalytic dehydration hydrogenation of chlorophyll accounts for 50 and 4 of the raney nickel phytane rnphy yield measured in suboxic sediments from the washington shelf and anoxic sediments from saanich inlet respectively if 8 20 of the pheopigment detected in the suboxic sediments and all of the pheopigment detected in the anoxic sediment exists as pheophytin the catalytic dehydration hydrogenation process would account for 100 and 50 respectively of the observed rnphy yield the collective findings from our work underscore the necessity to exercise extreme caution when interpreting the geochemical significance of hydrocarbon products from raney nickel treatment of ptel from sediments despite the organic chemical fact that raney nickel is a well known desulfurizing agent desulfurization cannot be assigned necessarily as the source of hydrocarbons generated by the action of this reagent on complex lipid extracts from sediments particularly those from modern environments

isotopic composition and speciation of sulfur in the miocene monterey formation reevaluation of sulfur reactions during early diagenesis in marine environments the timing and pathways of early diagenetic sulfur transfer from dissolved species in pore waters to solid inorganic and organic compounds in sediments have been studied in the miocene monterey formation santa maria basin onshore california correlation between concentrations of total organic carbon toc and total sulfur ts in addition to concentrations of titanium aluminum total iron and reactive iron have been used to infer organic matter reactivity redox conditions and relative rates of clastic and biogenic input for each lithofacies isotopic compositions of six sulfur species acid volatile disulfide kerogen bitumen sulfate and elemental have provided information regarding relative timing of sulfur incorporation sulfate diffusivity in the upper centimeters of the sediments and the sources of sulfur for individual species isotopically the disulfide species expresses the greatest fractionation relative to estimated values of miocene seawater sulfate 22 cdt on average disulfide is depleted in 34s by 10 4 relative to kerogen and by 9 9 relative to acid volatile sulfide the 34s of bitumen shows no systematic change relative to 34skeregon suggesting the presence of migrated bitumen isotopic similarity of sulfate and elemental sulfur to sulfides and bitumen indicates that sulfate and elemental sulfur are chemical and or biological oxidation products derived from sulfides and bitumen consistent ordering of isotopic values for sulfur species disulfide acid volatile sulfide kerogen indicates that pyrite precipitated nearest to the sediment water interface under mildly reducing conditions and with little or no decrease in sulfate concentration relative to seawater enrichment of 34s in acid volatile sulfide and kerogen sulfur resulted from formation of these species at greater depths or in restricted micro environments under more reducing conditions and with low concentrations of porewater sulfate the formation of acid volatile sulfide after pyrite but during early diagenesis is significant because it implies more strongly reducing conditions than are generally recognized in deep water marine sediments

sulfur diagenesis and partitioning in holocene peru shelf and upper slope sediments abstract sediments of the peru margin were sampled in two transects across the shelf and upper slope 75 to 1000 m in october of 1992 this region is characterized by high surface water productivity and consequent high organic carbon fluxes low terrigenous inputs as well as an intense oxygen minimum zone omz impinging on the slope at depths between 75 and 550 m sediments analyzed in this study were collected from one ship deployed box core and five submersible deployed push cores organic carbon toc concentrations in surface sediments range from 1 to 18 on a dry weight basis formation of pyrite begins at the sediment water interface swi maximum concentrations of pyrite sulfur in the cores from this study range from 0 5 to 1 8 wt concentrations of pyrite are influenced by availability of reactive iron and an oxidant capable of converting avs to pyrite highly reactive iron is stripped from terrigenous detritus in the core of the omz some of this iron may contribute to glauconite formation in sediments near the base of the omz where it is concentrated into a glauconitic green sand as a result of reworking and winnowing in a shallow water site 109 m at the upper edge of the omz high concentrations of pyrite total iron and iron aluminum ratios indicate that easily reduced iron species are available for sulfidation at the swi pyrite formation at this site is nearly complete in the upper 4 cm of the sediment in contrast pyrite concentrations are slightly lower at the surface of two of the deeper water sites at 309 m in the center of the omz and to a lesser extent at 671 m at the bottom edge of the omz and appear to be influenced in part by availability of reactive iron concentrations of acid volatile sulfides avs are low in all sediments 0 04 wt but are slightly elevated in sediments from the center of the omz the ratio of organic sulfur s org to organic carbon toc at the sediment surface of the cores examined here is remarkably constant 0 012 0 002 and within the range observed in marine biota 0 01 to 0 02 suggesting that organic sulfur at the swi is dominantly biogenic although s org toc ratios increase downcore there is no clear correlation between concentrations of organic sulfur and organic carbon below the swi there is also no clear relation between concentrations of organic sulfur and total iron organic sulfur concentrations vary from site to site 0 06 to 0 33 wt but are relatively constant downcore at any given site maximum concentrations are in cores from the center of the omz

sulfur carbon ratios and extractable organic matter of the middle proterozoic nonesuch formation north american midcontinent rift abstract the nonesuch formation ca 1 1 ga host to the white pine copper deposit is a generally organic rich unit of relatively wide extent selected strata away from mineralization were analyzed for their organic carbon and total sulfur contents and for the amount and composition of extractable organic matter sulfur to carbon ratios are covariant but the ratios of total sulfur to organic carbon are generally higher than those found for marine phanerozoic black shales deposited under oxic bottom water conditions the sulfur to carbon ratios and the intimate association fo framboidal pyrite and organic matter are suggested to be the result of bacterial sulfate reduction in the nonesuch sediments activity of sulfate reducing bacteria requires a supply of sulfate in the water column and implies that the depositional environment was not a low sulfate aqueous environment a marine embayment dominated more by sea water than riverine input is suggested as the environment of deposition based on the correlation of total sulfur and organic carbon the relatively high total sulfur content and on the absence of sedimentologic and geochemical criteria for saline lacustrine environments deposition of highly reactive organic matter in low concentrations coupled with high concentrations of reactive iron and the absence of bioturbation resulted in unusually efficient pyrite formation extractable organic matter in unmineralized nonesuch strata is interpreted to be autochthonous in origin homologous series of n alkanes and cyclohexyl alkanes regular isoprenoids and monomethyl branched alkanes were identified by gas chromatography ratios of pristane phytane pristane n c17 and phytane n c18 suggest relatively low thermal maturity for the overall unit with a slight increase in the level of thermal maturity from michigan westward to wisconsin the aliphatic character and high extractability of organic matter indicate that the petroleum potential of the nonesuch formation will be good to excellent if the organic rich facies thicken down dip under lake superior or into the southern extension of the rift

a 60 000 year record of environmental change for the wet tropics of north eastern australia based on the odp 820 marine core palynomorphs from the odp site 820 marine core have provided a detailed record of terrestrial environmental responses to glacial interglacial forcing over the last 250 000 years in the australian wet tropics the development of an accurate geochronological framework for this key sequence has proved challenging consequently different dominant forcing mechanism s have been proposed to drive environmental change in the low latitudes a new chronology for the last 60 000 years based on accelerator mass spectrometry radiocarbon c dates of pollen concentrate material and the existing marine isotope stage boundaries mis 4 to 1 has been produced this new chronology provides a robust geochronological framework for interpreting environmental records across the region in particular our age model helps to resolve several debates concerning the timing of climatic changes and their impacts on both the marine and the terrestrial systems as well as possible human arrival and associated impacts on the region s ecosystems our findings suggest c dating of terrestrial pollen concentrate in marine sediments is a valuable tool for resolving major chronological uncertainties in potentially diagenetically altered marine caco sediments and should play a role in future multi dating strategies copyright

the impact of extratropical transition on the downstream flow an idealized modelling study with a straight jet the interaction of a tropical cyclone undergoing extratropical transition et with the midlatitude synoptic scale flow is investigated using full physics numerical experiments with idealized initial conditions the emphasis is on the impact on the midlatitude flow downstream of the et event the midlatitude flow is represented by a balanced straight jet stream as the tropical cyclone approaches the jet a ridge trough couplet and a distinct jet streak form in the upper level flow a midlatitude cyclone develops rapidly downstream of the et system and the further evolution is characterized by downstream baroclinic development based on hovmoller diagrams the upper level development is interpreted as the excitation and subsequent dispersion of a rossby wave train on the potential vorticity gradient associated with the jet the characteristics of this wave train are sensitive to the structure of the jet and to moist processes in the midlatitudes the tropical cyclone undergoing et acts as a sustained forcing for the wave train and the structure of the et system impacts the development most significantly one to two wavelengths downstream of et piecewise inversion of potential vorticity complemented by the partitioning of the flow into its rotational and divergent parts is applied to assess the impact of the et system quantitatively both the cyclonic circulation and the outflow of the tropical cyclone are important contributors to the formation and amplification of the ridge trough couplet the outflow anomaly reduces the eastward motion of the ridge trough couplet significantly and thus promotes phase locking between the tropical cyclone and the upper level pattern copyright 2008 royal meteorological society

pore water distributions of dissolved copper and copper complexing ligands in estuarine and coastal marine sediments the distributions and seasonal variability of total dissolved cu tdcu and cu complexing ligands in sediment pore waters have been investigated at two contrasting sites in the chesapeake bay two ligand classes which differ on the basis of the conditional stability constants k9 of their cu complexes were detected at all depths at both sites at the sulfidic muddy mid bay sta m concentrations and values of log k9 ranged from 390 12 500 nm and 7 2 8 9 respectively for the stronger ligand class l1s and 75 6 420 nm and 6 2 7 9 for the weaker ligand class l2s at the bioturbated sandy sta s in the lower bay respective concentrations and values of log k9 ranged from 135 807 nm and 7 6 10 2 for l1s and 40 1 410 nm and 6 6 9 2 for l2s for comparison one pore water profile from a slope station off of the chesapeake bay also showed the presence of two ligand classes with respective concentrations and values of log k9 of 140 270 nm and 8 11 for l1s and 30 180 nm and 7 10 forl2s these ligands are in large excess relative to ambient tdcu concentrations 0 1 24 3 nm thereby maintaining very low inorganic cu concentrations typically 0 1 to 100 pm and a high degree of organic complexation 87 2 99 9 of cu in bay and slope sediment pore waters thus virtually all tdcu fluxing from these sediments is complexed during sediment water exchange a relatively small fraction of the tdcu is exchanged as inorganic species which are widely regarded as the most bioavailable form of cu higher ligand concentra tions at sta m suggest that sulfide or organic ligands containing reduced s contribute to the pool of complexing ligands however the exact nature and sources of the ligands in bay pore waters are not known the progressive increase in conditional stability constants of the cul 2s complexes from the mid bay to the slope sediments may reflect differences in biological or chemical processes at each site as well as differences in the type of cu complexing organic matter total ligand concentrations l1s 1 l2s are 15 to 100 times higher in the upper intervals of the pore waters relative to ligand concentrations in the bottom waters of the chesapeake bay 30 60 nm consistent with previous observations of fluxes of these ligands from the sediments to overlying waters these results suggest that sediments are potentially significant sources of cu complexing ligands to the overlying waters of the chesapeake bay and perhaps other shallow water estuarine and coastal environments copper complexing ligands released from sediment pore waters may play an important role in influencing cu speciation in overlying waters copyright 2000 elsevier science ltd

northern hemisphere 500 hpa trough merger and fracture a climatology and case study abstract the results of an objective climatology of 500hpa trough merger defined as the amalgamation of two initially separate vorticity maxima and trough fracture defined as the splitting of a single vorticity center into two separate vorticity centers are presented for the northern hemisphere the data source is the gridded national meteorological center nmc now the national centers for environmental prediction analyses available on cd rom on the nmc operational octagonal grid 381 km resolution at 60 n for the period september 1957 to may 1989 a total of 2152 3053 merger fracture events are identified merger and fracture events tend to occur preferentially in the band of middle latitude westerlies merger events exhibit a tendency to avoid major mountainous regions and show a somewhat higher frequency of occurrence downstream of these regions fracture events cluster somewhat over eastern ocean basins the southwestern united states and northwestern africa while also avoiding major mount

postlandfall tropical cyclone reintensification in a weakly baroclinic environment a case study of hurricane david september 1979 abstract an analysis is conducted from a potential vorticity pv perspective of the reintensification of tropical storm david over the northeastern united states in september 1979 david a major long lived hurricane originated near the cape verde islands in late august 1979 it made final landfall in georgia on 4 september 1979 and weakened rapidly thereafter the noteworthy aspect of david was its subsequent reintensification approximately 27 h after landfall as a warm core disturbance in a weakly baroclinic environment in this regard the redevelopment of david is unlike the classical extratropical transformation of a tropical storm in a strongly baroclinic environment that has been documented in the literature the authors analysis of the evolution of the dynamical tropopause subsequent to storm landfall revealed that david reintensified in response to tropopause lifting upward displacement of the dynamic tropopause ahead of a nondeepening and otherwise very weak upper tropospheric disturbance

reconstructing the rise of recent coastal anoxia molybdenum in chesapeake bay sediments abstract sporadic direct observations over a 50 yr period inadequately characterize the history of seasonal hypoxia and anoxia in chesapeake bay a large estuary threatened by eutrophication here we undertake a reconstruction of 20th century oxygen depletion in this estuary using mo concentrations in 210pb dated sediments cu concentrations are used to control for anthropogenic influences cores from the central channel display mild mo enrichments above crustal backgrounds up to 5 g g and strong cu enrichments up to 35 g g temporally cu enrichment mostly anthropogenic began earlier and stabilized in the last two thirds of the 20th century in contrast mo enrichment has grown during the last two thirds of the century molybdenum enrichment is mostly hydrogenic except in a section of the channel that receives additional mo from erosion of early miocene shore deposits two geochemical mechanisms promote mo enrichment manganese refluxing concentrates dissolved moo42 at the sediment water interface and sulfide substitution into moo42 produces thiomolybdates which can be fixed by particles the mo enrichment mechanisms operate primarily during periods when bottom waters are anoxic and thiomolybdate formation can occur near the sediment water interface this implies a temporal coupling between water column anoxia and mo fixation even though fixation occurs only within sediments the mo enrichment profiles suggest that chesapeake bay has experienced growing o2 depletion since the first half of the 20th century but especially after 1960

sulphur speciation in anoxic hypersaline sediments from the eastern mediterranean sea abstract the anoxic hypersaline tyro and bannock basins are among the most sulphidic bodies of water in the marine environment h2s 2 mm we report the distribution of elemental sulphur acid volatile sulphur avs organic polysulphides humic sulphur 0 5 m naoh extractable and pyritic sulphur in the sediments from these basins pyritic sulphur appears to be the main phase of inorganic reduced sulphur 50 80 of the total sulphur pool and is at the same level about 250 moles per gram dry weight in cores recovered from the two basins remarkably humic sulphur has been found to account for 17 28 of the total sulphur pool in the tyro basin and for 10 43 in the bannock basin sulphur isotope data show negative 34s values for both pyritic sulphur 34s 19 c to 39 and humic sulphur 34s 15 to 30 this indicates that both pyritic and humic sulphur originate from microbially produced hzs neither basin shows a significant correlation between pyritic sulphur and organic carbon suggesting syngenetic pyrite formation additionally the degree of pyritization in these sediments dop is 0 62 indicates that pyrite formation is limited by the reactivity of fe humic sulphur correlates with the pyritic sulphur distribution and seems to be related with gelatinous pellicles bacterial mats at the interface between oxic seawater and brine both pyritic and humic sulphur can be formed in the water column at the interface of oxic seawater and brine by a syngenetic pathway about 5 of the pyrite is formed in the sediments by diagenetic processes the presence of a bacterial mat and high hzs content in the brines favour such conditions however most of the humic sulphur inventory can be supported by diagenetic processes although these basins differ in their major element chemistry their reduced sulphur species chemistry appears to be similar

influence of a predecessor rain event on the track of tropical cyclone isaac 2012 abstractanalysis of a predecessor rain event pre over the straits of florida ahead of tropical cyclone tc isaac on 25 august 2012 is presented this pre is unique compared to previously documented pres in midlatitudes because it occurred over the oceanic subtropics and impacted the track of an approaching tc the isaac pre developed in conjunction with a tropical moisture plume with precipitable water values over 60 mm that intersected a region of mid and upper level frontogenesis and warm air advection on the southeast flank of an upper level trough the pre occurred in an environment with more abundant tropical moisture and weaker synoptic scale forcing for ascent compared to the environments in which midlatitude pres developed the isaac pre contributed to the fracture of the upper level trough through negative potential vorticity advection by convectively driven divergent outflow fracture of the upper level trough and midlevel cyclonic vorticity amplification associated with the pre acted to stee

a lightweight gravity corer for undisturbed sampling of soft sediments a lightweight portable gravity corer is described that collects up to 3 m long 10 cm diameter undistrubed cores from sediments of exceptionally high porosity the corer employs a triple o ring seal to hold sediments in an unsupported catcher free plastic barrel simply by suction author

the extratropical transition of hurricane irene 1999 a potential vorticity perspective extratropical transition et of tropical cyclones is common in all ocean basins where tropical cyclones recurve polewards after the tropical cyclone experiences et a rapid deepening can take place resulting in the development of a very large and deep extratropical cyclone the et of hurricane irene 1999 was an example of such an explosive et irene formed in the caribbean and experienced et as it moved poleward resulting in a low pressure system which deepened 39 hpa in 24 hours according to the met office analyses the extent to which the hurricane was responsible for the explosive extratropical development has been determined by performing met office unified model forecasts from initial states with and without the hurricane the circulation and temperature anomalies associated with the hurricane were removed from the initial state using potential vorticity inversion the moisture anomaly co located with the hurricane core was also removed the results show that an extratropical cyclogenesis event takes place regardless of the presence of the hurricane in the initial conditions however the hurricane makes a significant difference to the track and central mean sea level pressure evolution of the resulting extratropical cyclone when irene was present the track of the extratropical cyclone was more zonal and the cyclone deepening rate was twice as fast as when irene was not present these effects appear to be particularly associated with a negative potential vorticity anomaly and enhanced divergent flow in the region of the upper level outflow of the transforming hurricane rather than with the hurricane vortex results also show that the presence of the hurricane resulted in a significant downstream surface low development in the eastern atlantic copyright 2004 royal meteorological society

sulphur incorporation in jurassic marine mudrocks and their bitumens at low thermal maturity cleveland basin england abstract the distribution of sulphur between pyrite kerogen elemental sulphur and the aromatic fraction of mudrock bitumens has been quantitated in two cored sections of immature marine kimmeridgian strata which have experienced different levels of thermal stress strata in the two boreholes ebberston and reighton were deposited in different basinal settings basinal marine and platform respectively and occasional euxinic laminated horizons are present at ebberston otherwise dysoxic deposition was the norm at both localities pyrite the dominant sulphur carrier in all the mudrocks has a sulphur isotopic composition consistent with mineralisation in a system mainly open to sulphate diffusion kerogens are mostly low sulphur atomic s c and account for between 5 and 10 of rock sulphur although occasionally up to 30 kerogen sulphur is closely correlated with toc and highest in laminated mudrocks consistent with most effective sulphurization of kerogen under anoxic conditions although kerogen compositions in both cores vary with organic richness no systematic differences in organic input between the borehole localities are recognised geochemically some thermal effects on sulphur geochemistry are therefore interpreted from a comparison of stratigraphically equivalent sections from the two cores bitumen yields and abundances of aromatic sulphur in the more thermally stressed ebberston section although variable are generally much higher than in the reighton section and are partly related to kerogen sulphur content this is tentatively attributed to thermal release of additional extractable bitumen from macromolecules elemental sulphur s0 in bitumen is unrelated in abundance to other sulphur species and isotopically heavier than coexisting pyrite overprinting of minor preserved diagenetic s0 by secondary oxidation of pyrite appears likely the distributions of individual sulphur aromatic compound classes have features related both to maturity and stratigraphy

the influence of humic substances on the geochemistry of iodine in nearshore and hemipelagic marine sediments iodine is characteristically enriched at the surface of hemipelagic and nearshore sediments deposited under oxygenated conditions in such sediments bulk i corg ratios usually decrease with depth to values which are characteristic of anoxic sediments reflecting a preferential release of i during early diagenesis there is some debate as to whether sedimentary i is associated with the iron oxyhydroxide phase or with the organic fraction and whether the decrease in i corg with depth is due to the dissolution of the iron oxyhydroxides or the decomposition of labile organic matter it is shown that in a surficial hemipelagic sediment sample and in a nearshore sediment core i is mainly associated with the organic fraction and moreover that humic substances are involved in the surficial iodine enrichment laboratory experiments on the uptake and release of i by and from sedimentary humic substances also suggest a mechanism whereby humic materials reduce iodate at the sediment water interface to an electrophilic i species which further reacts with the organic matter to produce iodinated organic molecules during burial this excess i could be displaced from the organic matrix by nucleophiles such as sulphide ions or thiosulphate thus providing a possible explanation for the decrease in i corg ratio with depth observed in many nearshore and hemipelagic sediments

evolutionary changes over the last 1000 years of reduced sulfur phases and organic carbon in varved sediments of the santa barbara basin california abstract sediments from the santa barbara basin sbb of the last 1000 years were analyzed for elemental sulfur se mineral sulfide sulfur sm lipid based organically bound sulfur sx residual organically bound sulfur so total organic carbon toc and total nitrogen tn the approximate annual resolution of the time series data permitted us to evaluate the influence of oceanic variables on the benthic environment and the accumulating varved sediment in the sbb a bacterial mat community at or near the sediment surface is influencing sediment porosity and the production and distribution of se early diagenesis dampens the amplitude of environmental signals in the geochemical time series the concentrations of sm and so increase with burial depth at the expense of decreasing concentrations of sx and se at depths greater than 5 5 cm corresponding to an age of 7 years sm becomes the largest pool of reduced sulfur it requires approximately 500 years of primarily bacterially mediated diagenesis equivalent to a burial depth of 1 4 m for sbb sediments to gradually approach and finally enter the region assumed to represent typical normal marine sediments on a plot of weight percent toc vs sm

predecessor rain events over china s low latitude highlands associated with bay of bengal tropical cyclones a predecessor rain event pre is defined as organized heavy rainfall that occurs far ahead of tropical cyclone tc yet directly associated with the deep tropical moisture originating from the tc vicinity the pres occurring over china s low latitude highlands cllh in association with bay of bengal tcs were investigated from 1981 to 2012 results indicate that about 19 of bay of bengal tcs produces pre the pres frequently occur when tcs are active in the northern bay of bengal with northeastward paths the pres are more likely to appear in the pre monsoon and post monsoon seasons with peaks in may and october respectively the median lifetime of the pres was approximately two days the distances between pres and parent tcs are ranged from 745 to 1849 km with a median distance of 1118 km composite results of pres suggested that deep moisture is advected from the tc vicinity to the remote cllh region which is situated beneath the equatorward entrance of the upper level east asia subtropical jet easj the lower level southwesterly flow which is associated with a strong pressure gradient between the western pacific subtropical high and a trough in bay of bengal steers tcs conveying abundant moisture from the bay of bengal to the cllh region the enhancement of the ascent and frontogenesis within the equatorward entrance region of the easj is favorable for occurrence of pres in cllh tcs may also have a dynamical role in occurrence of pres by intensifying the upper level easj

sulfur speciation in the upper black sea sediments abstract we report solid phase sulfur speciation of six cores from sediments underlying oxic suboxic and anoxic sulfidic waters of the black sea our dataset includes the five sulfur species pyrite sulfur acid volatile sulfides avs zerovalent sulfur s 0 organic polysulfides rsx humic sulfur together with reactive iron and manganese as quantified by dithionite extraction and total organic carbon pyrite sulfur was the major phase in all cores 200 400 mol g dry wt 1 except for the suboxic core however zerovalent sulfur and humic sulfur also reached very significant levels up to about 109 and 80 mol g dry wt 1 respectively humic sulfur enrichment was observed in the surface fluff layers of the eastern central basin sediments where unit 1 type depositional conditions prevail elemental sulfur accumulated as a result of porewater sulfide oxidation by reactive iron oxides in turbidities from the anoxic basin margin and western central basin sediments the accumulation of elemental sulfur to a level close to that of pyrite s in any part of central black sea sediments has never been reported before and our finding indicates deep basin turbidites prevent the build up of dissolved sulfide in the sediment this process also contributes to diagenetic pyrite formation whereas in the non turbiditic parts of the deep basin water column formed syngenetic pyrite dominates the sulfur inventory in slope sediments under suboxic waters organic sulfur humic sulfur organic polysulfides account for 33 42 of total solid phase s indicating that the suboxic conditions favor organosulfur formation our study shows that the interactions between depositional patterns unit 1 vs turbidite redox state of overlying waters oxic suboxic sulfidic and organic matter content determine sulfur speciation and enable the accumulation of elemental sulfur and organic sulfur species close to a level of pyrite s

the early diagenetic formation of organic sulfur in the sediments of mangrove lake bermuda due to a low mineral content the sapropelic sediments depositing in mangrove lake bermuda provide an excellent opportunity to explore for possible additions of sulfur to organic matter during the early stages of diagenesis we evaluated early diagenetic organic sulfur transformations by monitoring the concentrations and stable isotopic compositions of a number of inorganic and organic sulfur pools thereby accounting for all of the sulfur in the sediments we have identified and quantified the following sulfur pools porewater sulfate porewater sulfide elemental sulfur pyrite sulfur hydrolyzable organic sulfur hyos chromium reducible organic sulfur cros and nonchromium reducible organic sulfur non cros of the organic sulfur pools the non cros pool is by far the largest followed by cros and finally hyos by 60 cm depth these pools contribute respectively to 85 7 9 and 3 6 of the total solid phase sulfur the hyos pool is probably of biological origin and shows no interaction with the sulfur compounds produced during diagenesis by contrast cros is produced most likely from the diagenetic addition of polysulfides to functionalized lipids in the upper h2s poor elemental sulfur rich region of the sediment a portion of this sulfur pool is unstable and decomposes on contact with the h2s rich porewaters the portion of cros that remains in the sulfidic waters appears to readily exchange sulfur isotopes with h2s while some of the non cros pool is of biological origin some is also formed by the diagenetic addition of sulfur to organic compounds in the upper h2s poor region of the sediment by contrast with cros non cros is not diagenetically active in the h2s rich porewaters overall somewhere between 27 and 53 of the organic sulfur buried in mangrove lake sediments is of diagenetic origin with the remaining organic sulfur derived from biosynthesis we extrapolate our mangrove lake results and calculate that in typical coastal marine sediments between 11 and 29 mol g 1 of organic sulfur will form during early diagenesis of which 2 5 mol g 1 will be chromium reducible

a study of sulphur enrichment in the humic fraction of marine sediments during early diagenesis abstract the evolution of the sulphur content of humic acids extracted from a near shore sediment core was investigated special attention was taken to avoid s contamination of the humic materials during extraction the s c ratios increased continuously with depth to values which strongly suggest s addition to the humic matrix during early diagenesis by reactions between organic matter and h2s or its oxidation products their light isotopic composition supports this view however subsequent isotopic exchange has obscured the mechanism initially involved since a large fraction of the enrichment occurred above the sulphidic zone redox boundaries such as the interface of anoxic microniches within more oxidized zones or the sulphidic suboxic boundary of the sediment column must have been important sites for s addition bioturbation by increasing the contact between sedimentary zones of a different redox regime will likely enhance such processes

extratropical transition of tropical cyclones over the western north pacific part ii the impact of midlatitude circulation characteristics abstract two characteristic midlatitude circulation patterns labeled northwest and northeast are found to be associated with extratropical transition et of tropical cyclones over the western north pacific ocean although in both cases the tropical cyclone moves poleward ahead of a midlatitude trough the primary midlatitude circulation is either that trough or is a large quasi stationary cyclone to the northeast of the poleward moving tropical cyclone transition into a northwest pattern typically results in the development within 36 h of an intense extratropical cyclone that moves north northeast a tropical cyclone that moves into a northeast pattern enters into strong zonal flow between the primary midlatitude circulation and the subtropical ridge to the southeast these systems move rapidly eastward and do not intensify significantly during the 36 h following transition in part i of this study the et of typhoon ty david 1997 and the et of ty opal 1997 were investigated in terms of the form

sulfidization of lacustrine glacial clay upon holocene marine transgression arkona basin baltic sea abstract towards the end of the last deglaciation more than 13 500 years ago the southern baltic sea was a freshwater lake the baltic ice lake for several thousand years during which iron rich organic poor clay was deposited the modern brackish marine stage started about 8600 years ago with the deposition of organic rich mud which is today characterized by high rates of sulfate reduction and high concentrations of free sulfide we studied the iron sulfur diagenesis in gravity cores from the arkona basin sw baltic sea to track the progressing sulfidization front in the buried ice lake sediment the geochemical zonation was unusual as the sulfate concentration dropped steeply by two thirds below which it increased again due to a deep sulfate reservoir the reservoir had been established during the early holocene marine period as sulfate and other seawater ions diffused down into the lake sediment for several thousand years sulfur isotope analyses confirmed its origin as seawater sulfate while its oxygen isotope composition indicated a microbially catalyzed equilibration with ambient interstitial water decoupled from net sulfate reduction today hydrogen sulfide diffuses from the marine mud down into the lake sediment where a black band with high magnetic susceptibility and high iron monosulfide greigite and elemental sulfur content shows progressing sulfidization of the large pool of solid phase reactive iron dissolved iron from the deep ice lake sediment diffuses up to the sulfide front and provides a small supplement to the solid fe iii pool as a sulfide sink pyrite formation at the sulfidization front may involve surface bound zero valent sulfur while above the front polysulfides are in equilibrium with the system hydrogen sulfide polysulfide rhombic sulfur and may not be important for further pyrite formation the holocene iron sulfur diagenesis observed in the arkona basin represents an important transitional state for post glacial transgressions with organic rich marine sediment overlying lacustrine clay such as in other areas of the baltic sea or in the black sea

mangrove forest evolution in a sediment rich estuarine system opportunists or agents of geomorphic change the majority of the world s mangrove forests occur on mostly mineral sediments of fluvial origin two perspectives exist on the biogeomorphic development of these forests i e that mangroves are opportunistic with forest development primarily driven by physical processes or alternatively that biophysical feedbacks strongly influence sedimentation and resulting geomorphology on the firth of thames coast new zealand we evaluate these two possible scenarios for sediment accumulation and forest development using high resolution sedimentary records and a detailed chronology of mangrove forest avicennia marina development since the 1950s cores were collected along a shore normal transect of known elevation relative to mean sea level msl activities for lead 210 pb 210 caesium 137 cs 137 and beryllium 7 be 7 and sediment properties were analysed with pb 210 sediment accumulation rates sars compensated for deep subsidence similar to 8 mm yr 1 used as a proxy for elevation gain at least four phases of forest development since the 1950s are recognized an old growth forest developed by the late 1970s with more recent seaward forest expansion thereafter excess 210pb profiles from the old growth forest exhibit relatively low sars near the top 7 12 mm yr 1 and bottom 10 22 mm yr 1 of cores separated by an interval of higher sars 33 100 mm yr 1 a general trend of increasing sar over time characterizes the recent forest biogeomorphic evolution of the system is more complex than simple mudflat accretion progradation and mangrove forest expansion surface elevation gain in the old growth forest displays an asymptotic trajectory with a secondary depocentre developing on the seaward mudflat from the mid 1970s two to ten fold increases in 210pb sars are unambiguously large and occurred years to decades before seedling recruitment demonstrating that mangroves do not measurably enhance sedimentation over annual to decadal timescales this suggests that mangrove forest development is largely dependent on physical processes with forests occupying mudflats once they reach a suitable elevation in the intertidal copyright c 2015 john wiley sons ltd

stable isotope geochemistry of crude oils and of possible source rocks from new zealand 2 sulfur abstract the sulfur isotopic composition of new zealand low s crude oils and components asphaltenes absorptive filtration fractions and source rock components extracted hydrocarbons kerogen pyrite sulfates were determined oils from the taranaki basin have 34s values from 3 to 14 o the lower values possibly represent plant assimilation of fresh water sulphate higher values particularly those from the west coast basin around 20 suggest closed ocean basin conditions or fast sedimentation rate whereas negative 34s values from east coast basin suggest open ocean or low sedimentation rate conditions it is suggested than an oil source rock relation should show as a similarity in 34s values for total oil and source rock extract kerogen and pyrite shale samples analysed plot outside the corresponding oil range and cannot be considered as possible source rocks however coal samples from the maui 4 well and nelson outcrops show strong isotopic correlations with the taranaki oils

interactions of thiols with sedimentary particulate phase studies of 3 mercaptopropionate in salt marsh sediments from shelter island new york abstract 3 mercaptopropionate 3 mpa is a major hydrophilic thiol in salt marsh sediments from shelter island new york it is associated mainly with the sedimentary particulate phase although the mechanism of its binding has not been clear in this study we show that humic substances coated on clay minerals are involved in binding 3 mpa through di and poly sulfide linkages with increasing depth the abundance of 3 mpa in the fulvic acid fraction decreases with a concomitant increase in the humic acid fraction suggesting that with depth fulvic bound 3 mpa is converted into humic bound 3 mpa we modeled the depth variation with a multi g model which suggests that there are two types of reactive components in both fulvic acid bound and humic acid bound 3 mpa one changing about 10 times more rapidly than the other these two 3 mpa pools probably reflect different types of sulfur bridging with the polysulfide bridged pool changing more rapidly than the disulfide bridged pool as free thiol 3 mpa is attacked relatively rapidly by anaerobic bacteria its degradation following firstorder kinetics however in the sediment core we studied humic bound 3 mpa was present throughout the sediment column down to 22 cm corresponding to an age of about 90 years these results suggest that thiols can escape bacterial degradation in sediments by binding to humic substances the sedimentary distribution of 3 mpa is an important illustration of the interplay of biological and chemical processes in the fate of thiols in anoxic marine sediments

hydrological transformation coincided with megafaunal extinction in central australia central to the debate over the extinction of many of australia s last surviving megafauna is the question was climate changing significantly when humans arrived and megafauna went extinct here we present a new perspective on variations in climate and water resources over the last glacial cycle in arid australia based on the study of the continent s largest lake basin and its tributaries by dating paleoshorelines and river deposits in the lake eyre basin we show that major hydrological change caused previously overflowing megalakes to enter a final and catastrophic drying phase at 48 2 ka just as the giant bird genyornis newtoni went extinct 50 45 ka the disappearance of genyornis and other megafauna has been previously attributed to ecosystem collapse coincident with the spread of fire wielding humans our findings suggest a climate driven hydrological transformation in the critical window of human arrival and megafaunal extinction and the results call for a re evaluation of a humanmediated cause for such extinctions in arid australia

non steady state diagenesis of organic and inorganic sulfur in lake sediments abstract sulfur controls the fate of many geochemical elements in lake sediments including iron phosphorus and environmentally important trace elements we measured the speciation of pore water and sediment bound sulfur aqueous sulfate and sulfides elemental sulfur iron monosulfide pyrite organic sulfur and supporting geochemical variables carbon oxygen iron in the sediments of a perennially oxygenated and a seasonally anoxic basin of an oligotrophic lake in quebec using a combination of pore water analyses sequential extractions and x ray absorption near edge structure a non steady state early diagenetic model was developed and calibrated against this extensive dataset to help unravel the pathways and quantify the rates of s transformations results suggest that the main source of s to the sediments is the settling of organic ester sulfate r o so3 h hydrolysis of these compounds provides an additional source of sulfate for anaerobic microbial oxidation of sedimentary organic matter releasing sulfide to the pore water reduced solid bound s species accumulate as thiols r sh and iron sulfides in the perennially oxygenated and seasonally anoxic basin respectively the model estimated rate constant for r sh formation is lower than previously estimated for this particular lacustrine site but similar to that proposed for marine shelf sediments the solid sediment s profiles however carry the imprint of the time dependent sulfate input to the lake iron sulfide enrichments formed during past decades of elevated atmospheric so4 deposition are presently dissolving in the sediments of the perennially oxygenated basin this reaction hampers the build up of fe iii oxy hydroxide near the sediment water interface

extratropical transition of tropical cyclones over the western north pacific part i evolution of structural characteristics during the transition process abstract the development of extratropical cyclone structural characteristics that resulted from the extratropical transition of typhoon ty david 1997 and ty opal 1997 over the western north pacific is examined david moved poleward ahead of a midlatitude trough that was moving eastward as the dominant midlatitude circulation feature over the western north pacific during the transition david coupled with the midlatitude trough which led to the evolution of an intense cyclone that became the primary circulation over the north pacific although opal also moved poleward ahead of a midlatitude trough the principal midlatitude feature over the western north pacific was a preexisting stationary cyclone over the kamchatka peninsula during transition opal weakened and became a secondary cyclone to the preexisting primary north pacific cyclone the structural characteristics of the evolving extratropical cyclone with respect to each case are examined in the context of the interaction between a vortex an

jellyfish lake palau regeneration of c n si and p in anoxic marine lake sediments sediment cores from jellyfish lake were processed under an inert atmos phcre and the pore waters extracted and analyzed for the following parameters ph titration alkalinity ta cl h4si04 pod3 nh4 ca2 mg2 sod2 and h2s additionally in one set of pore water samples core lo the 613c of the x0 was also determined the ta h4si04 pod3 nh and h s increased with depth in the pore waters above anoxic bottom water values h s values increased to 3 8 pm in one case both h sio and pod3 concentrations increased to a maximum value and then decreased with depth suggesting removal into solid phases the h sio concentrations are equal to or greater than pore water values observed in sediments underlying upwelling areas pod3 concentrations are in general lower than pore water values from terrigenous nearshore areas but higher than nearshore carbonate pore water values from florida bay or bermuda the ca2 cl and mg2 cl ratios show slight decreases in the top 15 20 cm suggesting that authigenic carbonate may be forming this suggestion is supported by the fact that the pore waters are saturated with respect to caco due to the very high tas the 613c measurements of the pore water x0 are from a shorter core these measurements reach their most negative concentration at 72 cm and tilen become slightly heavier this change is accompanied by a decrease in ta suggesting the onset of methanogenesis at this location in this core

heavy precipitation associated with southern appalachian cold air damming and carolina coastal frontogenesis in advance of weak landfalling tropical storm marco 1990 abstract an analysis is presented of tropical storm marco 1990 a storm that dropped copious amounts of rain over the southeast united states marco was noteworthy because of its role in the formation and evolution of two distinct episodes of cold air damming and coastal frontogenesis over georgia and the carolinas these mesoscale features led to greater than 300 mm of precipitation in 2 days over the near coastal southeast united states much of the rain occurred while marco was over 400 km away this case is further complicated by two other nearby tropical cyclones which affected marco s track and the overall rainfall distribution synoptic and mesoscale analyses of the development of the coastal front and cold air damming episodes show that the location of marco helped to orient low level winds toward the appalachians as rain developed inland a pocket of relatively cool air the cool pool formed near the mountain slopes and was partially blocked by the higher terrain low level analyses show t

a stable isotope study of pyrite formation in the late pleistocene and holocene sediments of the black sea the abundance and isotopic composition of total and pyrite sulphur have been determined in a core in the central black sea pyrite varies in concentration from roughly 2 wt in the sapropel unit 2 to 0 8 wt in the modern horizon unit 1 and ca 0 1 wt in the lowermost horizons of unit 3 lake beds an intermediate mud flow horizon and the upper part of the lake beds have similar values to those in the modern sediments the degree of pyritization dop is lowest 0 05 in the lower lake beds and highest 0 55 in unit 1 the sapropel has values of ca 0 48 34spyrite varies from a minimum of 37 in the sapropel to 33 in unit 1 up to 15 in the upper lake beds and 0 in the lower lake beds the unit 1 and sapropel values are similar to the 34s values reported by fry et al 1991 of dissolved sulphide immediately below the water column oxic anoxic interface 36 to 38 but significantly heavier than those in the deep waters of the basin ca 41 these results are interpreted as a reflection of the presence of four different types of pyrite in the sediments of the black sea 1 pyrite in units 1 and 2 that is formed within the upper part of the water column immediately below the oxic anoxic interface where 34s of dissolved sulphide is 36 2 pyrite in the mud flow layer lying between unit 1 and the sapropel unit 2 with a significantly heavier isotopic composition that was formed around the margins of the basin under conditions that were probably more closed with respect to dissolved sulphate than those in which the pyrite in units 1 and 2 were formed 3 pyrite in the upper part of the lake beds unit 3 that was formed under closed system conditions by reaction between excess reducible fe remaining in these freshwater sediments and downward diffusing sulphate and or sulphide from the overlying organic rich sapropel and 4 pyrite in the lower part of the unit 3 representing a phase formed from the ambient sulphate in the freshwaters of the late pleistocene lake the isotopic information supports earlier suggestions that pyrite in the modern sediments of the black sea forms mainly in the water column with only minor amounts forming in the sediment because of the severe fe limitation of the bottom sediments that accumulate 2 000 m below the main fe and hs reaction zone at the oxic anoxic interface at shallow depths in the water column

appalachian cold air damming abstract appalachian cold air damming is investigated by means of 1 a 50 yr monthly climatology 2 a synoptic case study of the event of 21 23 march 1985 and 3 an investigation of the flow structure and force balance within the cold dome the climatology reveals cold air damming is a year round phenomenon in the southern appalachians with the most frequent prolonged and intense events occurring in winter particularly december and march when three five events per month can be expected cold air damming is least frequent and intense in july the synoptic case study reveals that cold air damming is critically dependent upon the configuration of the synoptic scale flow the cold dome can be identified by a u shaped ridge trough in the sea level isobar thermal patterns and the 930 mb height temperature fields representative of conditions at the base of the inversion overlying the cold dome differential horizontal and vertical thermal advection as well as adiabatic and evaporative cooling are r

composition of organic sulfur in riverine and marine sediments insights from sulfur stable isotopes and xanes spectroscopy abstract sulfur isotopes and x ray absorption near edge structure xanes spectroscopy were combined to characterize compare three operational organic sulfur os pools i e fulvic acid sulfur fa s humic acid sulfur ha s and non chromium reducible organic sulfur non cros in marine the east china sea ecs and jiaozhou bay jzb vs riverine yangtze river yr and jzb tributaries sediments xanes results indicate that in marine sediments high valency s was the dominant os functionality in both ha s and fa s while non cros was dominated by low valency os 80 92 in the riverine sediments fa s was dominated by high valency os while the average fractions of low and high valency os in ha s were comparable the isotopic composition of fa s 34 s fa s and ha s 34 s ha s indicated that a substantial fraction of sulfide was incorporated into fa via sulfurization in the marine sediments whereas terrigenous os was almost the sole important source of ha s compared with the ecs sediments jzb sediments had more depleted 34 s fa s and a higher fraction of highly reduced fa s due to eutrophication induced sulfurization relative to riverine fa s substantial sulfurization had not resulted in an increase in the fraction of highly reduced fa s in marine sediments this implies that the terrestrial systems may be much more favorable for the formation and or preservation of highly reduced biogenic fa s than the marine settings the fraction of highly reduced ha s in the jzb and its tributaries was similar whereas the fraction was much lower in the ecs than in the yr this indicates that highly reduced ha s moieties in the yr may have been subject to extensive mineralization loss during transport in the large riverine estuarine system whereas the process in the jzb tributaries may be much weakened due to a relatively small catchment area distinct differences in isotopic and structural composition between humic s fa s ha s and non cros in the ecs sediments indicate that a combination of s isotopes and s xanes is needed for characterizing the two operational pools for a better understanding the nature of os in the ocean

the extratropical transition and precipitation distribution of hurricane floyd 1999 abstract several recent landfalling tropical cyclones e g dennis floyd and irene 1999 have highlighted a need for a refinement in the forecasting paradigms and techniques in the area of quantitative precipitation forecasting floyd proved to be a particularly challenging forecast problem as it was accompanied by catastrophic flooding over large regions of the east coast in spite of its relatively quick northward movement the extent and intensity of the precipitation distribution was strongly modulated by the storm s interaction with a midlatitude trough in an attempt to better understand and quantify the relevant dynamics during this interaction potential vorticity pv and quasigeostrophic perspectives are utilized as floyd approached the east coast precipitation shifted to the left of the storm track due to the presence of a deep midlatitude trough in the ohio valley the juxtaposition of a cold core pv anomaly associated with the midlatitude trough and a warm core pv anomaly associated with

synoptic scale environments of predecessor rain events occurring east of the rocky mountains in association with atlantic basin tropical cyclones abstractthe synoptic scale environments of predecessor rain events pres occurring to the east of the rocky mountains in association with atlantic basin tropical cyclones tcs are examined pres that occurred during 1988 2010 are subjectively classified based upon the synoptic scale upper level flow configuration within which the pre develops with a focus on the following 1 the position of the jet streak relative to the tc 2 the position of the jet streak relative to trough and ridge axes and 3 the positions of trough and ridge axes relative to the pre and to the tc three categories were identified from this classification procedure jet in ridge southwesterly jet and downstream confluence pre relative composite analysis for each category reveals that consistent with previous studies pres typically occur near a low level baroclinic zone beneath the equatorward entrance region of an upper level jet streak and in the presence of a stream of water vapor from a tc despite these common

remote impact of north atlantic hurricanes on the mediterranean during episodes of intense rainfall in autumn 2012 autumn is the most favourable season for tropical cyclones to undergo extratropical transition and interact with the midlatitude flow over the north atlantic autumn is also the season when intense rainfall over the mediterranean is often triggered by rossby wave breaking the impact of tropical cyclones on downstream wave breaking is investigated here during three episodes of intense rainfall which were the target of hymex hydrological cycle in mediterranean experiment in autumn 2012 five day simulations of hurricanes leslie rafael and sandy were performed with the meso nh model in a domain encompassing the north atlantic and the mediterranean control simulations were compared to simulations in which the hurricanes were filtered out from the initial conditions in each case the hurricane locally impeded the forward progression of an upstream trough then reintensified as an extratropical cyclone during the wrap up of the trough the local impact of leslie and rafael on the midlatitude flow quickly propagated downstream along a polar jet and amplified rossby wave breaking but decreased the intensity of the forecast precipitation over the mediterranean the local impact of sandy propagated downstream along a subtropical jet in addition to the polar jet and resulted in a weak impact of the forecast precipitation on the mediterranean this study suggests that the interaction of tropical cyclones with the midlatitude flow over the western north atlantic may be considered a perturbation to rather than a source of downstream wave breaking

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

determination of organic degradation rates in 100 my old sediments application to cretaceous black shale intervals from demerara rise odp leg 207 abstract thick organic rich albian to santonian black shale sequences were recovered from ocean drilling program sites 1261 and 1257 on the demerara rise offshore surinam at depths of 564 and 174 m below seafloor bsf respectively total organic carbon toc concentration varies between 3 9 and 17 3 wt rock eval pyrolysis parameters and elemental analysis indicate that the kerogen samples are of type ii thermally immature and with well preserved organic matter the hydrogen index hi values fluctuate between 608 and 765 mg hydrocarbon hc g toc and correlate well with c n and the sorg c atomic ratios indicating varying early diagenesis conditions between samples higher c n and sorg c values for kerogen from site 1261 suggest more reducing depositional conditions than at site 1257 long term organic diagenesis is marked by a linear decrease in the oxygen index oi at site 1261 from 34 to 22 mg co2 g toc ester and carboxyl functional groups are the main target of the degradation as inferred from the decrease in c o and o c c fourier transform infrared spectroscopy ftir bands as well as in the ch oh and the o ch3 chx n bands in 13c nuclear magnetic resonance nmr spectra degradation rate at site 1261 determined combining quantitative nmr spectra and bulk elemental characterization is between 1 7 and 12 1 mol m3 yr per 1 toc at the lower end of reported rates in a similar context kerogen samples from site 1257 do not show any decrease in oxygen content with depth indicating significantly lower degradation rate we propose that the long term exposure to moderate temperature 30 c at site 1261 activated the organic matter thereby sustaining microbial diagenesis

massive siliciclastic discharge to slopes of the great barrier reef platform during sea level transgression constraints from sediment cores between 15 s and 16 s latitude and possible explanations abstract the northeast australian continental margin including the great barrier reef gbr platform provides an outstanding modern analogue for understanding sedimentation in tropical mixed siliciclastic carbonate depositional systems previous studies of cores from this margin have suggested that in contrast to widely accepted models maximum siliciclastic fluxes to slopes over the last 30 ky occurred when sea level transgressed the shelf ca 11 7 ka rather than when sea level was at a lowstand before 18 ka however climate and bathymetry can affect regional sediment deposition significantly and the cores examined to date have come from the southern queensland trough where the margin has a wet tropical climate and a broad shelf 50 km with gradual slopes in this study we examine the abundance and accumulation of siliciclastic material in four cores from lower slopes of the northern queensland trough where rivers drain a drier region and debouche onto a narrow shelf with steep incised slopes similar to previously examined cores all cores contain a dark greyish brown horizon within the upper few meters this horizon represents a low in carbonate content and corresponding high in siliciclastic material primarily clay and oxygen isotope stratigraphy shows that it was deposited during late transgression nominally between 11 and 7 ka moreover mass accumulation rate calculations demonstrate that this horizon reflects a significant rise in siliciclastic fluxes when combined with the previous work to the south it appears that slopes all along a large portion of the northeast australian continental margin received greatly enhanced inputs of siliciclastic material during late transgression independent of proximal climate and bathymetry two general explanations are offered for this observation 1 climate change induced highly variable riverine discharge over the past 30 ky with a prominent maximum coincident with late transgression or 2 the shelf stores large quantities of siliciclastic sediment during lowstand and releases this material to the slope during late transgression in either case siliciclastic accumulation on the northeast australia continental margin behaves completely opposite to predictions from conventional models

on the squall lines preceding landfalling tropical cyclones in china abstractbased on a 3 yr 2007 09 mosaic of radar reflectivity and conventional surface and synoptic radiosonde observations the general features of squall lines preceding landfalling tropical cyclones tcs pre tc in china are examined and compared with their midlatitude and subtropical counterparts the results show that about 40 of landfalling tcs are associated with pre tc squall lines with high occurring frequency in august and from late afternoon to midnight most pre tc squall lines form in a broken line mode with a trailing stratiform organization on average they occur about 600 km from the tc center in the front right quadrant with a maximum length of 220 km a maximum radar reflectivity of 57 62 dbz a life span of 4 h and a moving speed of 12 5 m s 1 pre tc squall lines are generally shorter in lifetime and length than typical midlatitude squall lines pre tc squall lines tend to form in the transition area between the parent tc and subtropical high in a moist environment and with a weak

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

saturate biomarkers and aromatic sulfur compounds in oils and condensates from different source rock lithologies of kazakhstan japan and russia abstract representative petroleums from the seven basins of kazakhstan russia and japan were analyzed using gas chromatography with dual fid fpd and gc ms the present study has shown that the deviation in relative concentrations of aromatic sulfur compounds in petroleums could be related to the type of source rock all oil samples were classified into three groups on the basis of the relative abundance of aromatic sulfur compounds biomarker distribution and lithology of source rock the first group of oils derived from carbonate source rocks is rich in aromatic sulfur compounds such as methylbenzothiophenes mbt and methyldibenzothiophenes mdbt and poor in dibenzothiophene dbt compared to methylated homologs the second group derived from siliceous and siliceous carbonate source rocks contains various types of benzothiophenes and dibenzothiophenes including dbt the third group originating from argillaceous rocks has lower concentrations of aromatic sulfur compounds and especially of methylated benzothiophenes

speciation and stable isotopic compositions of humic sulfur in mud sediment of the east china sea constraints on origins and pathways of organic sulfur formation abstract humic sulfur is commonly the most important pool of organic sulfur os in marine sediments and also important for the budget of total sedimentary sulfur in this study contents and stable sulfur isotopic compositions of hydrolyzable organic sulfur hyos humic acid sulfur ha s and fulvic acid sulfur fa s in one core collected from the east china sea ecs inner shelf were determined to investigate the sources and pathways of os formation and to compare diagenetic geochemistry of ha s and fa s hyos in the core is essentially biological in origin and diagenetically refractory with a fairly low fraction of labile sulfur bearing biomolecules ha s in the core is largely terrigenous residual bio os while fa s is a mixture of marine bio and diagenetic os diag os with the diag os fractions between 44 and 71 both ha s and fa s contents in the core are at the lower ends of the corresponding values reported in the literature the ha in the sediments is diagenetically inert subject to neither significant diagenetic sulfurization nor bio os mineralization loss while the fa is reactive prone to both sulfurization and decomposition loss of diagenetically bound os low contents of humic s i e ha s fa s in the core may suggest that os burial has only minor contribution to the burial of total sulfur in the sediments due to generally low om sulfurization

a study on the regulation of the concentrations of some trace metals rb sr zn pb cu v cr ni mn and mo in saanich inlet sediments british columbia canada abstract bulk metal concentrations were measured in the sediments of saanich inlet in an attempt to establish the occurrence of trace metal enrichment in the anoxic central basin ba ni v cr zn pb cu and mo were found to be enriched in the anoxic ooze over the possible contributions from lithogenic sources spatial and seasonal variations in the chemical composition of the settling particulates collected with interceptor traps gave further indications of the mode of incorporation of these metals biogenic ba and cr appeared to be associated with opaline silica although alternative explanations are also possible particularly for ba zinc seemed to be added to the sediment essentially in association with planktonic materials while cu required an additional source directly linked to the anoxic environment similarly ni v and mo were added to the anoxic sediments by reactions occurring at the sediment water interface in the nearshore environment studied here these metals particularly ni and mo were not associated to any significant extent with planktonic materials of all the elements analyzed mo showed the largest enrichment in the anoxic sediments of saanich inlet

sources and dynamics of sulfur in weathered till western glaciated plains of north america abstract at three sites in the western glaciated plains warman and luck lake in saskatchewan canada and bow river in alberta canada thick 30 m till sequences contain 0 3 0 8 s by dry weight in the unweathered zone depths 2 5 15 m 65 90 of this s is cr reducible pyrite the remainder largely organic s is enriched in 34 s by 6 12 relative to the pyrite at the bow river site both pyrite and organic s are enriched in 34 s by up to 9 relative to samples of the same fractions from the warman and luck lake sites this may reflect a higher content of non marine parent material in southern alberta till at the warman site the sources and dynamics of sulfur in the weathered zone were investigated during weathering of the floral formation till sulfate was produced by the oxidation of pyrite and to a lesser extent by mineralization of organic s based on the distribution of so 4 in the landscape at warman three settings have been distinguished upland leached channel depression and saline ring the upland setting has a 9 m thick weathered zone which contains abundant so 4 mainly as secondary gypsum sulfate has been leached downward from the upper 2 m creating a peak accumulation of gypsum at 3 m sulfate has been leached from the entire 2 5 m deep weathered zone in the channel depression setting by seasonal infiltration of snow melt and lateral flow in contrast at 3 4 m depth in the weathered zone at the edge of the channel so 4 has accumulated as a saline ring here the gypsum s is up to 1 of the soil dry weight in the weathered zone of upland and saline ring settings the 34 s values of the so 4 in sediment extracts water soluble and groundwater 13 1 to 9 0 are very similar to those of the total s 12 0 to 11 4 and pyrite s 16 0 to 10 1 of unweathered floral formation till this indicates an in situ weathering source of the so 4 in contrast the 34 s of so 4 in sediment extracts and groundwater from the leached weathered zone of the upland and channel depression settings 7 7 to 4 5 is enriched in 34 s relative to unweathered floral formation till s this enrichment may be attributed to either 1 isotope fractionation during oxidation of pyrite and or 2 mineralization of residual organic s which is 34 s enriched after pyrite was weathered away

hydrogen index as reflecting intensity of sulphidic diagenesis in non bioturbated shaly sediments abstract based on 13 published porewater h 2 s and sulphate profiles the amount of h 2 s escaping from non bioturbated shales varies between some few to 45 of the amount of bacterially generated h 2 s this finding permits calculation of the original organic carbon toc or content of immature nonbioturbated shales using toc and sulphur content data in two immature non bioturbated sequences from hungary toarcian and oligocene the first order correlation between hi and toc toc or was found to be stronger than that between hi and toc indicating that sulphate reduction was the leading process both in decrease in toc content and degradation of kerogen source potential

organic sulphur fixation in freshwater lake sediments and the implication for us ratios a comparative analysis of two sediment cores from perialpine lakes l zurich and l geneva helped to clarify pathways of sulphur fixation in freshwater sediments despite greater than three fold differences in lake water sulphate concentration equal amounts of sulphur are fixed in the sediments the maximum sedimentary sulphur concentrations attain 1 dry weight which is similar to the sulphur content of modem near shore marine sediments this is also expressed in low corg stot ratios which range from 2 5 8 an analysis of the sulphur pools showed that organic sulphur compounds are the main components of the sedimentary sulphur accounting for 80 and 60 of the total sulphur in lakes zurich and geneva respectively the largest single sulphur pool is the sulphate esters which comprise 40 60 of the total sedimentary sulphur substantial amounts of the organic sulphur compounds must be formed within the sediment by boundary layer microbial communities at the oxic anoxic transition zone this possibly suggests rapid recycling of sulphur in suboxic zones because of low concentration of so24 in the watermass the zone of sulphate reduction is very thin this coupled with the mobility of some sulphide oxidizing microbial colonies e g beggiutoa potentially results in an almost complete recycling of the sulphur pool near the sediment water interface reduced sulphur caught in this cycling process is unavailable for sedimentary pyrite formation the corg spyriteratios for these sediments are thus high if organically bound sulphur is not completely transformed into pyrite during late diagenesis the corg spyrite ratio can serve as a sensitive indicator for the salinities of anaent depositional environments

early diagenetic alteration of organic matter by sulfate reduction in quaternary sediments from the northeastern arabian sea abstract hemipelagic sediments from the northeastern arabian sea off pakistan were analyzed by geochemical and microscopical methods to study the importance of bacterial degradation processes on the quantity and composition of sedimentary organic matter om on the basis of elemental analysis of total organic carbon toc and total sulfur ts the decay of om by sulfate reducing bacteria were calculated concentrations of total iron reactive iron total nitrogen tn total phosphorus tp and hydrogen indices hi were used to assess organic matter reactivity and redox conditions stable sulfur isotopic compositions provided further information about pathway timing and mechanisms of sulfate reduction microscopical observations indicate that throughout the study area om is amorphous 75 95 in almost all samples with only a small contribution of terrigenous om bacterially mediated sulfate reduction leads to continuously decreasing toc ts ratios from 0 4 m to a burial depth of 2 3 m at this depth the anaerobic oxidation of particulate organic matter ceases sulfate reduction in this narrow interval accounts for the decay of up to 70 of the om which has primarily entered the anoxic domain during the bacterially mediated diagenesis preferential consumption of nitrogen and phosphorus containing organic compounds can be observed and quantified the regeneration of up to 60 of tn and more than 50 of tp can lead to a feedback of nutrients to the seawater this recycling process may contribute to the high productivity in the northeastern arabian sea

sulphide speciation in surface sediments of the lagoon of venice a geochemical and mineralogical study abstract three 1 m cores of recent sediments from the lagoon of venice were sampled to obtain the vertical distribution of fe zn cu pb and cd and to study authigenic iron sulphides from the geochemical and mineralogical viewpoints zn cu pb and cd occur in superficial sediments in concentrations many times higher than those of their natural background the existence of zn cd and cu pb couples were revealed by their very similar depth profiles the latter couple is also closely correlated with sulphide sulphur iron is characterized by quite a different behaviour showing a sharp increase at a depth of 35 cm from a geochemical viewpoint authigenic sulphides were distinguished into pyrite and acid volatile sulphides greigite and mackinawite their distribution is characterized by high concentrations of avs in the first 25 cm of sediments dramatically decreasing with depth pyrite present in lower amounts shows the opposite trend although in one core both species were present in comparable amounts mineralogical study of the heavy mineral fraction revealed that the iron sulphides are composed of pyrite organised both in the classic framboidal growth and in unordered micro crystal swarms and iron mixed sulphide aggregates with variable optical patterns and colloform botroidal or massive growth no heavy metals were detected in the crystalline lattice of the sulphides down to 25 cm all types of sulphides occur and with increasing depth pyrite clearly prevails this behaviour may have various causes e g chemico physical control by specific microniches temporal and spatial variations favouring the formation of different types evolution of iron mixed sulphides into more stable forms

organization and environmental properties of extreme rain producing mesoscale convective systems this study examines the radar indicated structures and other features of extreme rain events in the united states over a 3 yr period a rainfall event is defined as extreme when the 24 h precipitation total at one or more stations surpasses the 50 yr recurrence interval amount for that location this definition yields 116 such cases from 1999 to 2001 in the area east of the rocky mountains excluding florida two kilometer national composite radar reflectivity data are then used to examine the structure and evolution of each extreme rain event sixty five percent of the total number of events are associated with mesoscale convective systems mcss while a wide variety of organizational structures as indicated by radar reflectivity data are seen among the mcs cases two patterns of organization are observed most frequently the first type has a line often oriented east west with training convective elements it also has a region of adjoining stratiform rain that is displaced to the north of the line the second type has a back building or quasi stationary area of convection that produces a region of stratiform rain downstream surface observations and composite analysis of rapid update cycle version 2 ruc 2 model data reveal that training line adjoining stratiform tl as systems typically form in a very moist unstable environment on the cool side of a preexisting slow moving surface boundary on the other hand back building quasistationary bb mcss are more dependent on mesoscale and storm scale processes particularly lifting provided by storm generated cold pools than on preexisting synoptic boundaries

water column anoxia enhanced productivity and concomitant changes in δ13c and δ34s across the frasnian famennian boundary kowala holy cross mountains poland the investigation of the trace element and organic geochemistry of the frasnian famennian boundary section at kowala holy cross mountains poland shows that the lower water column was oxygen deficient during late frasnian and early famennian times the abundance and carbon isotopic composition of diaryl isoprenoids biomarkers indicative for green sulfur bacteria prove that euxinic waters reached into the photic zone at least episodically total organic carbon toc contents show two maxima that are time equivalent to the kellwasser horizons deposited in shallower water settings enhanced toc concentrations are explained by a higher primary productivity presumably as a consequence of an enhanced nutrient supply from the continent the increase in the abundance of hopanes and bituminite suggests that the bacterial contribution to toc increased at the frasnian famennian transition the sulfur isotopic composition of pyritic and organically bound sulfur shows a 27 excursion across the boundary the observation that the 34s values of organic bound sulfur closely resemble that of pyrite sulfur indicates a common sulfur source likely early diagenetic sulfide a change in the 13c of total dissolved inorganic carbon as a consequence of an enhanced burial of 12c enriched organic carbon is indicated by a 3 excursion measured for toc as well as for individual n alkanes and isoprenoids the burial of large amounts of organic carbon is expected to result in a decrease in pco2 and should affect the photosynthetic carbon isotope fractionation ep the fact that we observe no change in ep can be explained by the circumstance that ep was most probably at maximum values as a consequence of high atmospheric and oceanic dissolved co2 concentrations during the devonian

interactions of north pacific tropical midlatitude and polar disturbances resulting in linked extreme weather events over north america in october 2007 abstractthis study uses observations and model reanalyses to examine the multiscale processes associated with four high impact extreme weather events ewes over north america during late october 2007 the ewes consisted of wind driven wildfires in california prolonged anomalous cold conditions in mexico linked to two cold surges heavy rainfall in the eastern united states and severe flood producing heavy rainfall in southern mexico the ewes involved a pronounced large scale flow reconfiguration across the north pacific and north america in conjunction with the formation of a high amplitude rossby wave train the flow reconfiguration involved perturbations to the north pacific jet stream linked to polar midlatitude and tropical disturbances including three tropopause level polar disturbances originating over northeastern asia transient extratropical cyclones a diabatic rossby vortex and western north pacific tropical cyclone kajiki eulerian and lagrangian diagnostics indicate that ridge amplifi

geomorphology of submerged reefs on the shelf edge of the great barrier reef the influence of oscillating pleistocene sea levels the submerged reefs on continental margins and surrounding oceanic islands are important archives of past climates eustatic sea level oscillations and oceanographic processes australia s north eastern submerged shelf edge reefs have previously been explored but all studies have been limited by either low resolution single beam profiles or by their limited spatial extent the aim of this study is to improve the understanding of the origin and development of submerged shelf edge reefs terraces and related features on the great barrier reef gbr and the influence of pleistocene sea level oscillations on their distribution and geomorphology we investigated the first large scale 1400 km2 3d bathymetry and acoustic backscatter dataset of four widely spaced sites located across ca 650 km along the shelf edge at ribbon reefs 1 5 noggin pass viper reef and hydrographers passage we provide a comprehensive description and systematic classification of the shelf edge features and constrain their spatial distribution and geomorphologic variability using a wide range of quantitative morphometrics fifteen features are defined four of which are the focus of this study including terraces pinnacles ridges and channels using modern reefs within the gbr for comparison we interpret these as fringing reefs patch and barrier reefs and tidal channels respectively the influence of gross shelf geomorphology and oceanographic factors driving the observed variability within and between sites is discussed in conjunction with mid late pleistocene sea level oscillations we observed two distinct types of reef growth characterised by the degree of development which we interpret as analogous to juvenile and mature modern reefs of the gbr juvenile reefs are very common and occur within each site at depths of less than 50 m to greater than 100 m they are defined as discontinuous peaked barrier reefs peaked patch reefs and fringing reefs mature reefs are less common and develop exclusively at a depth range of ca 50 70 m these reefs are defined as flat topped continuous barrier and double barrier reefs through a comparison with published mid late pleistocene sea level oscillations we note that the depth range of mature reefs is consistent with the depth of repeated low amplitude 20 m eustatic sea level oscillations and independent of the relative time spent at sea level we conclude that repeated low amplitude sea level rises provide the much needed accommodation space for vertical accretion that is not provided during stillstands without inducing reef drowning which can be caused by high amplitude sea level rise low amplitude sea level falls are also less detrimental than high amplitude falls in terms of habitat compression together the effects of enhanced reef accretion and limited habitat compression at depths of 50 70 m have lead to a concentrated net gain in vertical relief that is not observed elsewhere on the shelf edge

organic matter preservation and sulfur uptake in sediments from the continental margin off pakistan abstract the bulk and molecular geochemical characteristics of a suite of kerogens isolated from organic matter rich sediments from the pakistan margin has been characterised by elemental analysis rock eval pyrolysis and pyrolysis gas chromatography py gc special attention was given to the geochemistry of alkylthiophenes which are thought to reflect the incorporation of sulfur into organic matter om in the context of early diagenetic sulfate reduction organically bound sulfur comprises up to 60 of total sedimentary sulfur the weight ratios for organic sulfur s org over organic carbon c org varies from 0 01 in some of the recently deposited sediments to 0 11 in older samples the results show that sulfur incorporation into organic matter occurs primarily within the upper few meters of the sediments the amount of sulfur which can be incorporated into the organic matter clearly depends on the quality of om the hydrogen index values hi which characterise the total amount of generated hydrocarbon equivalents of the pyrolysate in mg hc equiv g c org are related to the extent of reworking of organic matter either in the water column or at the sediment water interface or to remineralization processes by sulfate reduction itself which is strongly controlled by the availability of reactive iron high quality organic matter characterised by elevated hi values is capable of sequestering higher amounts of sulfur as expressed by the thiophene content which represent the organically bound sulfur of the pyrolysate in mg g c org as indicated by the ratio of thiophenes versus hi which characterises the proportion of thiophenes in the total pyrolysate sulfurisation of organic matter seems to be terminated at a ratio of 0 01

carbon and sulfur relationships in marine senonian organic rich iron poor sediments from israel a case study abstract in fe poor and organic rich marine sediments reduced s is mainly organic due to the lack of reactive fe these sediments e g carbonates cherts phosphates have high c s organic carbon total reduced sulfur ratios which are as a rule 3 and may reach 5 or 6 at times even 10 in organic rich rocks these high ratios are characteristic for these fe barren sediments and are very different from those found in marine sediments where pyritic s is the main reduced sulfur species they may be explained by the escape of h 2 s to the atmosphere the interpretation of c 1bs plots in these sediments is also quite different one reason for the s intercept in these plots is the presence of pyritic s and thus contrary to the conventional plots this intercept seems to have no environmental significance on the other hand the s c slope appears to be a paleoenvironmental indicator low slopes 0 2 indicate restricted to normal aerobic environments c 1bs plots have been used to interpret environments of deposition in such sediments from two cycles of organic rich fe poor senonian sediments in several basins in central and southern israel both cycles appear to have been deposited in restricted environments the campanian mishash formation environments of deposition appear to be in general more oxic than those of the maastrichtian ghareb formation as an independent comparison for the c s results the degree of pyritization dop was calculated for some samples the dop results confirmed the c s results it should be stressed that in such low fe environments even dop results should be used with caution

extratropical transition of southwest pacific tropical cyclones part i climatology and mean structure changes a database of tropical cyclone best track and intensity information for the southwest pacific ocean basin is used to construct a 28 year climatology for tropical cyclones that move into middle latitudes of the nine or so tropical cyclones that form each year an average of about three can be expected to migrate south of 358s with the greatest fraction in march storms entering the tasman sea west of new zealand nz move almost due south on average and retain greater intensity than those to the east of nz where storms decay quickly while moving rapidly away to the southeast storms east of nz are embedded in a stronger more zonal flow than those to the west which move poleward ahead of a larger amplitude trough during el nino years tropical cyclones that move into middle latitudes exhibit stronger zonal motion and occur over a wider range of longitudes than during la nina years storm intensity is only weakly correlated with concurrent sst anomalies suggesting that atmospheric circulation is the dominant influence on storm properties average structure changes during extratropical transition et are identified using the ncep ncar reanalysis dataset for a subset of 33 transitioning storms during 1980 97 composites are used to construct a three dimensional conceptual model of the transformation from a mature hurricane to an asymmetric baroclinic midlatitude cyclone southwest pacific tropical cyclones encounter the baroclinic westerlies early in their lives accounting for their average eastward and poleward motion at maximum average intensity near 208s baroclinic effects are already important with warm frontogenesis appearing in the southeast quadrant and outflow aloft into a downstream subtropical wind maximum that moves poleward with the storm by 258s the average tc has lost the characteristic symmetric anticyclonic outflow aloft and acquired the characteristics of a baroclinic midlatitude storm including regions of warm and cold frontogenesis a vertical motion dipole and a westward tilt with height from about 308s poleward a second upper tropospheric wind maximum appears west of the storm with strengthening cyclonic vorticity advection aloft below about 400 hpa the storm retains the vertical warm cyclonic core as it migrates poleward

mineralization of organogenic ammonium in the monterey formation santa maria and san joaquin basins california usa abstract inorganic fixed ammonium nh4 contents as high as 0 28 wt were measured in organicrich quartz grade siliceous rocks of the miocene monterey formation from the santa maria and san joaquin basins california the greatest amount of fixed nh4 was found in rocks associated with hydrocarbons in the point arguello and lost hills oil fields where the nh 4 nh 4 k molar ratio of bulk samples ranges from 0 17 0 35 the formation of nh4 illite is suggested by the parallel increase in the percent of illite in the mixed layered illite smectite i s and in the nh 4 nh 4 k molar ratio of the clay sized fraction with increasing burial depth mineralization of nh4 appears to be promoted by the coincident timing of the smectite to illite clay mineral transformation and the release of nh4 during catagenesis nh4 feldspar may form at shallow burial depths in rocks from the point arguello field that contain a greater amount of detrital k feldspar and in which the i s contains only 10 20 illite quartzgrade siliceous monterey rocks from coastal outcrops in the lions head area lack significant amounts of hydrocarbons and have nh 4 nh 4 k molar ratios of 0 14 0 21 rocks from the lions head area show a strong positive correlation between diagenetic illite and fixed nh4 contents with nh4 constituting 18 21 mol of the fixed interlayer cations in the i s low grade opal a and opal ct siliceous miocene rocks from coastal outcrops in the pt pedemales area have low fixed nh4 contents 0 01 wt because these rocks contain minor amounts of diagenetic k bearing minerals i s contains 10 illite and they lack significant amounts of generated or migrated hydrocarbons the increase in the organic c n ratio with burial depth most likely reflects the preferential release of n compared to c and suggests that nh4 release is greatest during shallow burial bacterial degradation and deep burial catagenesis oil generation the results of this study support the suggestion of williams et al 1989 that high fixed nh4 contents may provide a long term geologic record of low temperature

sedimentary sulfur geochemistry of the paleogene green river formation western usa implications for interpreting depositional and diagenetic processes in saline alkaline lakes abstract the sulfur geochemistry of the lacustrine paleogene green river formation colorado utah and wyoming usa is unlike that of most marine and other lacustrine rocks distinctive chemical isotopic and mineralogical characteristics of the formation are pyrrhotite and marcasite high contents of iron mineral sulfides strikingly enriched in 34 s cyclical trends in sulfur abundance and 34 s values and long term evolutionary trends in 34 s values analyses that identified and quantified these characteristics include carbonate free abundance of organic carbon 0 13 47 wt total iron 0 31 13 wt reactive iron 70 of total iron total sulfur 0 02 16 wt acid volatile monosulfide s av disulfide s di 70 of total sulfur sulfate s so 4 and organosulfur s org isotopic composition of separated sulfur phases 34 s di av up to 49 and mineralogy morphology and paragenesis of sulfide minerals mineralogy morphology 34 s di av and 34 s org have a distinctive relation reflecting variable and unique depositional and early diagenetic conditions in the green river lakes when the lakes were brackish dissimilatory sulfate reducing bacteria in the sediment produced h 2 s which initially reacted with labile iron to form pyrite framboids and more gradually with organic matter to form organosulfur compounds during a long lived stage of saline lake water the amount of sulfate supplied by inflow decreased and alkalinity and ph of lake waters increased substantially extensive bacterial sulfate reduction in the water column kept lake waters undersaturated with sulfate minerals a very high h 2 s so 4 ratio developed in stagnant bottom water aided by the high ph that kinetically inhibited iron sulfidization progressive removal of h 2 s by coeval formation of iron sulfides and organosulfur compounds caused the isotopic composition of the entire dissolved sulfur reservoir to evolve to 34 s values much greater than that of inflow sulfate which is estimated to have been 20 a six million year interval within lake uinta cores records this evolution as well as smaller systematic changes in 34 s interpreted to reflect 100 000 year lake level cycles when porewater was exceptionally reducing unstable fes phases eventually recrystallized to pyrrhotite during diagenesis a much later reaction related to weathering altered pyrrhotite to marcasite

early diagenesis and sulphur speciation in sediments of the oman margin northwestern arabian sea the pore waters from two boxcores from the oman margin from sites niop484 and niop487 respectively in and below the oxygen minimum zone in the water column were analysed for concentrations of iodide sulphide thiosulphate phosphate silica ammonia nitrate nitrite dissolved iron dissolved manganese and dissolved sulphur in addition the solid phase of samples from the same cores was analysed for organic carbon pyritic sulphur acid volatile sulphide elemental sulphur organic polysulphides humic sulphur reactive iron phases and reactive manganese phases pore water profiles show that post oxic diagenesis dominates in these holocene sediments only minor amounts of reduced sulphur species were found in pore waters despite the low oxygen concentration of the bottom water and the relatively high organic matter content of the sediments significant amounts of solid phase reduced sulphur were only found in the lower half of the boxcore at station niop484 consequently sulphate reduction is not as significant in these sediments relative to sediments from other upwelling areas and thus more sedimentary organic matter is preserved

humic sulfur in eutrophic bay sediments characterization by sulfur stable isotopes and k edge xanes spectroscopy abstract organic sulfur os is an important sedimentary sulfur pool in marine sediments and chemical extractions are often used for quantification of various os pools however os sources and mechanisms of os formation are not well understood in this study sulfur stable isotope and sulfur x ray absorption near edge structure xanes spectroscopy were combined to investigate the sources and speciation of humic acid sulfur ha s and fulvic acid sulfur fa s in sediments of eutrophic jiaozhou bay whilst there may be some indication that eutrophication has enhanced fa s burial in the sediment this has not substantially modified the characteristically low humic sulfur i e ha s fa s contents of the sediments sulfur isotopic compositions indicate that both ha s and fa s are mixtures of diagenetic and biosynthetic os in origin ha s is dominated by biosynthetic sulfur and fa s by diagenetic source sulfur isotopic compositions and contents of pyrite and diagenetic os indicate that inhibition of sulfurization by pyrite formation if any appears insignificant xanes analysis suggests that the contents of high oxidized os i e sulfones and ester sulfates and strongly reduced os species are comparable in the ha s whereas the fa s is dominated by strongly reduced os as a result of enhanced sulfurization

geochemistry of rare earth elements in a marine influenced coal and its organic solvent extracts from the antaibao mining district shanxi china twenty six samples including roof bottom and coal plies of a marine influenced coal bed were collected from the antaibao mining district shanxi china the rare earth elements rees were determined in solids and organic solvent extracts the distribution pattern showed three distinct patterns shale like lree rich and hree rich this is attributed to the variable microenvironment of peat forming swamp the degree of marine influences and different ree sources rees in the coal are mainly controlled by detrital minerals but also affected by seawater the chondrite normalized ree patterns of the organic solvent extracts are distinctly different from those of corresponding original coal samples which show a negative eu anomaly a depletion of middle rees and an enrichment of hrees the lrees in coal extracts are likely adsorbed by hydrogen containing functional groups and hrees are likely bonded to carbon atoms

sulphur and iron geochemistry of holocene coastal peats nw germany a tool for palaeoenvironmental reconstruction abstract a drill core from the marshlands of nw germany covering the entire holocene was analysed at high resolution by geochemical xrf cirm ms and microfacies methods diatoms thin sections sem in order to provide information about the palaeoenvironmental development in addition microbial experiments were carried out with sulphate reducing bacteria srb and cellulose fermenting fungi in seawater using peat as substrate the core contains an intercalated reed peat layer 2 73 3 02 m and a basal peat 5 78 6 42 m the basal peat consists in the lowest part of fen woodland and raised bog peat while the upper part is formed by a reed peat bed the peat layers are characterised by a distinct enrichment of pyrite with negative bulk sediment 34 s values av 11 5 range 2 6 to 26 7 reflecting microbial sulphate reduction in some peat intervals under almost open system conditions with respect to the input of seawater sulphate pyrite occurs exclusively with framboidal texture in close vicinity to the organic matter which indicates localised pyrite formation at the decay site in microenvironments with high concentrations of dissolved fe microbial experiments reveal that peat does not represent an appropriate substrate for srb and that srb have to rely on the preceding decomposition of peat by other microorganisms in microenvironments the total sulphur content of the peat layers averages to 7 8 wt with a maximum value of 28 2 wt unusually found within the basal peat at the transition of fen woodland and raised bog peat the pyrite enrichments can be explained by two different scenarios which are related to the intensity of the sea level rise the first scenario applies to a moderate sea level rise and is decisive for the reed peats where pyrite formation coincides with peat growth a brackish zone is assumed for the peat forming environment which is influenced by iron rich freshwater and sulphate rich seawater as the freshwater forms the major fe source the amounts of pyrite increase to a certain degree with decreasing salinity in this environment the palaeosalinity is estimated by the investigation of littoral and pelagic diatoms the second scenario applies to the extensive pyrite formation within the basal peat at the transition of fen and bog peat this pyrite was likely formed after peat growth favoured by a steep sea level rise thin sections of this peat interval reveal clastic layers 1 3 mm with completely pyritised interfaces as these clastic layers contain marine pelagic diatoms e g paralia sulcata we propose that they are caused by tidal channel activities during a phase of a steep sea level rise the marine incursion led to a partial buoyancy of the basal peat at weak transition zones i e the transition from fen to bog peat as a result of the bouyancy marine suspended particulate matter can be introduced laterally in between the peat sections when the peat settles down a clastic layer remains whose interface with the peat may have favoured the inflow of waters of higher salinity therefore an enhanced formation of pyrite was possible due to the combination of sulphate rich ground water and iron rich peatland waters

tropical view of quaternary sequence stratigraphy siliciclastic accumulation on slopes east of the great barrier reef since the last glacial maximum generic models of continental margin evolution predict that siliciclastic fluxes to slopes should be maximal and minimal during major sea level lowstands and transgressions respectively here we document the opposite for the northeast australian margin the largest extant mixed siliciclastic carbonate depositional system cores from slopes of this margin consistently contain siliciclastic rich intervals 0 3 1 m thick in the upper few meters radiocarbon dates of planktonic foraminifera show that this interval was deposited between 12 and 7 ka and represents greatly increased siliciclastic fluxes during late transgression this massive terrigenous discharge to slopes occurred along at least 450 km of the margin irrespective of modern variations in bathymetry or climate although we cannot dismiss a significantly different early holocene climate with greatly enhanced sediment discharge available data instead suggest that rivers aggraded on the shelf during lowstand because of an extensive subaerially exposed reef system this phenomenon may occur on other margins rimmed by reefs requiring a major revision of concepts used to interpret mixed siliciclastic carbonate systems

enhanced trapping of molybdenum by sulfurized marine organic matter of marine origin in mesozoic limestones and shales there have been many studies devoted to trace metals and their value in assessing the paleoredox conditions of ancient marine deposition among them molybdenum mo is frequently cited as an effective proxy for sediments and sedimentary rocks recently helz et al helz g r miller c v charnock j m mosselmans j l w pattrick r a d garner c d vaughan d j 1996 mechanisms of molybdenum removal from the sea and its concentration in black shales exafs evidences geochim cosmochim acta 60 3631 3642 and adelson et al adelson j m helz g r miller c v 2001 reconstructing the rise of recent coastal anoxia molybdenum in chesapeake bay sediments geochim cosmochim acta 65 237 252 suggested that mo does not behave conservatively in the water column when h2s reaches a threshold concentration above this concentration a switch operates and mo is scavenged by forming bonds with metal rich notably iron particles sulfur rich organic molecules and pyrite in this paper mo trapping by sulfur rich organic matter om in ancient marine deposits is emphasized the following mesozoic geological formations were selected for study because of their relatively high concentration of sulfurized om the akkuyu formation turkey the calcaires d orbagnoux france and kimmeridge clay uk and its timeequivalent in boulonnais france the kashpir oil shales russia and the la luna formation venezuela the sulfur rich om is identified by either measured organic s abundance or kerogen microscope observation our results show that mo is systematically more enriched relative to the other redox sensitive sulfide forming elements studied u v ni cu zn cr and mo enrichment is positively correlated with the amount of sulfurized om but not with pyrite abundance these results illuminate the role played by sulfurized om in geologic scale mo capture and retention but they also underline the role played by reactive iron significant om sulfurization is only possible when reactive iron is limited nevertheless pyrite formation though limited could act as an initial mo trap prior to mo uptake by om that is sulfurized after the pyritization step in future paleoenvironmental reconstructions attention must be paid to this enhanced mo enrichment in the presence of sulfurized organic matter in such cases the use of mo could lead to overestimation of the reducing conditions of the depositional environment

paired organic matter and pyrite δ34s records reveal mechanisms of carbon sulfur and iron cycle disruption during ocean anoxic event 2 abstract the sulfur s isotope composition of pyrite in the sedimentary record has played an important part in our understanding of the evolution of biogeochemical cycles throughout earth history however the kinetics of pyritization are complex and depend strongly on the reactivity and mineralogy of available iron as a second major sink for sulfide in anoxic sediments organic matter om provides essential context for reconstructing the distribution and isotopic composition of environmental sulfide to first order roughly parallel pyrite and om 34 s profiles reflect changes in sulfide while independent patterns require alternative explanations including changes in iron availability or om characteristics we apply this framework to ocean anoxic event 2 oae 2 94 mya a period of enhanced burial of reduced c and s in om and pyrite that has been associated with an expansion of reducing marine conditions we present paired s isotope records for pyrite and om along with profiles of om s c ratio and s redox speciation from four well characterized lithologic sections with a range of depositional environments pont d issole cismon tarfaya basin and demerara rise to reconstruct both local redox structure and global mechanisms impacting the c s and fe cycles around oae 2 om sulfurization appears to be a major control on om preservation at all four sites similar to modern anoxic environments there is a positive correlation between om s c ratios and toc concentrations for sites with more reducing conditions implying a link between om sulfurization and burial at consistently anoxic sites like tarfaya basin and demerara rise strongly sulfurized om with a consistent s redox speciation and s isotope composition most likely formed rapidly in sinking particles before during and after oae 2 particle hosted om sulfurization may therefore have been a central mechanism facilitating the massive burial of om in anoxic environments during this and other periods of enhanced global carbon burial at the same time a nearly 25 negative shift in the 34 s values of pyrite but not om occurs at multiple globally distributed sites prior to the onset of oae 2 indicating slower pyritization reactions that likely reflect changes in iron delivery due to expanding regional or global anoxia the combination of pyrite and organic s isotopes thus provides novel constraints on the interwoven cycles of carbon iron and sulfur across a major carbon cycle perturbation