stable carbon isotope patterns of marine biomarker lipids in the arctic ocean during eocene thermal maximum 2 the middle paleocene through early eocene long term gradual warming was superimposed by several transient warming events such as the paleocene eocene thermal maximum petm and eocene thermal maximum 2 etm2 both events show evidence for extreme global warming associated with a major injection of carbon into the ocean atmosphere system but the mechanisms of carbon injection and many aspects of the environmental response are still poorly understood in this study we analyzed the concentration and stable carbon isotopic delta c 13 composition of several sulfur bound biomarkers derived from marine photoautotrophs deposited in the arctic ocean at similar to 85 degrees n during etm2 the presence of sulfur bound biomarkers across this event points toward high primary productivity and anoxic bottom water conditions the previously reported presence of isorenieratene derivatives indicates euxinic conditions in the photic zone likely caused by a combination of enhanced primary productivity and salinity stratification the negative carbon isotope excursion measured at the onset of etm2 for several biomarkers ranges between 3 and 4 5 much larger than the similar to 1 4 recorded in marine carbonates elsewhere suggesting substantial enhanced isotopic fractionation by the primary producers likely due to a significant rise in pco 2 in the absence of biogenic carbonates in the etm2 section of our core we use coeval planktonic delta c 13 from elsewhere to estimate surface water delta c 13 in the arctic ocean and then apply the relation between isotopic fractionation and pco 2 originally calibrated for haptophyte alkenones to three selected organic biomarkers i e s bound phytane c 35 hopane and a c 25 highly branched isoprenoid this yields pco 2 values potentially in the range of four times preindustrial levels however these estimates are uncertain because of a lack of knowledge on the importance of pco 2 on photosynthetic isotopic fractionation

lacustrine basin dynamics and organosulphur compound origin in a carbonate rich lacustrine system late oligocene mequinenza formation se ebro basin ne spain abstract the late oligocene mequinenza formation se ebro basin ne spain records the development of extensive shallow low gradient lacustrine zones which evolved under a subtropical warm climatic regime affected by humidity aridity cycles carbonate dominated inner lacustrine sequences which include thin coal seams are laterally related to muddy carbonate and siliciclastic marginal lacustrine assemblages where evaporites occur water solute concentration of the lacustrine zones changed during the alternative high and low stand episodes with lacustrine waters ranging mainly from fresh to oligosaline nonsulphurised nsc and sulphurised osc organic compounds occur in the inner lacustrine facies and record significant contributions from aquatic and terrestrial higher plants bacteria cyanobacteria photosynthetic anaerobic bacteria and algae these biomarkers show that the lacustrine system was eutrophic and the water column was poorly oxygenated and sometimes stratified as evidenced by occasional finely laminated facies and gammacerane organic matter s c ratio lower in carbonate than in coal and coal related facies suggests significant variations in the lacustrine autotrophic production and or the allochthonous organic matter contribution higher plant biomarkers were recorded mainly as normal nonsulphurised lipids by contrast bacterial and algal lipids hopanoids steroids and isoprenoids under intense sulphate reduction conditions incorporated sulphur in their hydrocarbon skeleton and gave rise to osc with distributions of thienyl and thiolanylhopanoids epithiosteranes and polyprenoids linear thiols are new biomarkers which probably were generated by the early incorporation of sulphur into funtionalised precursors e g alkanols intense methanogenesis was enhanced in some lacustrine zones owing to high organic matter input and as a consequence biomarkers of methanotrophic and methylotrophic bacteria related to methane emission are also found

nondestructive in situ cellular scale mapping of elemental abundances including organic carbon in permineralized fossils the electron microprobe allows elemental abundances to be mapped at the mm scale but until now high resolution mapping of light elements has been challenging modifications of electron microprobe procedure permit fine scale mapping of carbon when applied to permineralized fossils this technique allows simultaneous mapping of organic material major matrix forming elements and trace elements with mm scale resolution the resulting data make it possible to test taphonomic hypotheses for the formation of anatomically preserved silicified fossils including the role of trace elements in the initiation of silica precipitation and in the prevention of organic degradation the technique allows one to understand the localization of preserved organic matter before undertaking destructive chemical analyses and because it is nondestructive offers a potentially important tool for astrobiological investigations of samples returned from mars or other solar system bodies

molecular isotopic characterisation of hydrocarbon biomarkers in palaeocene eocene evaporitic lacustrine source rocks from the jianghan basin china immature organic matter in lacustrine source rocks from the jianghan basin eastern china was studied for distributions and stable carbon isotopic compositions 13 c of hydrocarbon biomarkers all of the bitumens contain isorenieratane 13 c ca 17 indicating the presence of chlorobiaceae and thus periods of euxinic conditions extended into the photic zone aliphatic hydrocarbon fractions are dominated by pristane and phytane and contain relatively low amounts of 4a and 4 methylsteranes c 30 13 c ca 16 believed to originate from 4 methylsterols in dinoflagellates 13 c values of gammacerane ca 24 and c 30 17 21 h hopane ca 23 are consistent with an origin from bacterivorous ciliates that fed on chlorobiaceae the bitumens contain low relative amounts of organo sulphur compounds one rock contains c 37 and c 38 n alkanes 13 c ca 36 derived from alkadienes and alkenones of prymnesiophytes the distributions of hydrocarbon biomarkers suggest that they were initially sulphurised during early diagenesis and later released during early thermal maturation

early diagenesis of organic matter and related sulphur incorporation in surface sediments of meromictic lake cadagno in the swiss alps samples of recent anoxic sediment 100 yr bp from the meromictic lake cadagno switzerland were examined to study sulphur incorporation into organic matter at a very early stage of diagenesis trace amounts of two organosulphur compounds were identified in the extractable organic matter desulphurization of the heterocompound and asphaltene fractions with nickel boride yielded hydrocarbons with a strong dominance of phytane and minor amounts of n alkanes steranes and squalane but may also have converted ester bound moieties into hydrocarbons as shown by a control experiment with a chloropyll a standard the amount of sulphur bound compounds is always higher than the amount of the free precursors even in the shallowest sediments this indicates that the formation of organosulphur compounds starts already in the water column or is very effective in the uppermost millimeters of the sediment layer stable carbon isotope data of the sedimentary compounds and of biological material from the water column and from land biota growing around the lake show that the sulphur bound phytane in the youngest samples is dominated by phytane of bacterial origin with increasing depth the amount of phytane of terrestrial origin slightly increases

impact of dia and catagenesis on sulphur and oxygen sequestration of biomarkers as revealed by artificial maturation of an immature sedimentary rock hydrous pyrolysis of an immature ro 0 25 sulphur rich marl from the gessoso solfifera formation messinian in the vena del gesso basin was carried out at 160 c t 330 c for 72 h to study the effect of progressive diagenesis and early catagenesis on the abundance and distribution of sulphur containing and sulphur and oxygen linked carbon skeletons in low molecular weight and high molecular weight fractions e g kerogen to this end compounds in the saturated hydrocarbon fraction monoaromatic hydrocarbon fraction polyaromatic hydrocarbon fraction alkylsulphide fraction and ketone fraction were quantified as well as compounds released after desulphurisation of the polar fraction and hilialh4 treatment of the desulphurised polar fraction sulphur bound phytane and 20r 5 14 17 h and 20r 5 14 17 h c27 c29 steranes in the polar fraction become less abundant with increasing maturation temperature whereas the amount of their corresponding hydrocarbons increases in the saturated hydrocarbon fraction carbon skeletons that are bound in the kerogen by multiple bonds e g c38n alkane and isorenieratane are first released into the polar fraction and then as free hydrocarbons these changes occur at relatively low levels of thermal maturity ro 0 6 as evidenced by the immature values of biomarker maturity parameters such as the c35 hopane ratio and the 22s 22s 22r 17 21 h c35 hopane ratio sulphur and oxygen bound moieties present in the polar fraction are not stable with increasing thermal maturation however alkylthiophenes ketones 1 2 di n alkylbenzenes and free n alkanes seem to be stable thermal degradation products of these sulphur and oxygen bound moieties thus apart from free n alkanes which are abundantly present in more mature sedimentary rocks and crude oils alkylthiophenes 1 2 di n alkylbenzenes and ketones can also be expected to occur the positions of the thiophene moiety and the carbonyl group coincide with the original positions of the functional groups of their precursors thus important information about palaeobiochemicals is retained throughout the sequestration degradation process

identification of a novel c25 highly branched isoprenoid thiophene in sediments a novel c25 highly branched isoprenoid hbi thiophene 2 2 methylpropyl 4 9 2 6 12 trimethyltetradecyl thiophene has been identified in three sediment samples by isolation followed by characterization by 1h nmr gc ms and raney ni desulphurization this component is probably formed by incorporation of inorganic sulphur species into a specific sedimentary c25 hbi alkadiene this latter compound is probably derived from diatoms

sulfides in petroleum abstract the homologous series of terpenoid sulfides previously reported to be present in athabasca bitumen have been detected in a variety of petroleums from the western hemisphere all 22 samples examined ranging in age from devonoan to cretaceous contained the terpenoid sulfides a method is described for the isolation of sulfides from petroleums based on the selective oxidation of sulfides to more polar sulfoxides which are easily removed from the mixture and their subsequent reduction to sulfides the sulfide content in the petroleum maltenes examined ranged from 0 3 to 16 1 w w in addition to the bicyclic and tetracyclic terpenoid sulfides a new series of tricyclic terpenoid sulfides has been identified and the details of the isoprenoid side chain have been elucidated for all three homologous series the distributions by carbon number of the bicyclic and tetracyclic homologous series of terpenoid sulfides show pronounced variations which are attributed to thermal maturity and degree of water washing of the petroleum thus the ability to identify terpenoid sulfides should provide a useful tool for oil oil and oil source rock correlation studies the bicyclic and tricyclic terpenoid sulfides have the same carbon framework as the carotenoids which suggest that these sulfides were accessory pigments in photosynthesis

steroid biological marker hydrocarbons as indicators of organic matter diagenesis in deep sea sediments geochemical reactions and influence of different heat flow regimes specific geochemical transformation reactions of steroid hydrocarbons have been chosen to illustrate the molecular evolution of organic matter in deep sea sediments the progression of isomerisation of 5 4 sterenes 20r 20s diasterenes 20r 20s spirosterenes and 14 14 monoaromatic anthrasteroids with depth has been monitored in core samples from ten dsdp sites areas with high geothermal gradients are compared to those with low geothermal heat flow the formation of regular sterenes and anthrasteroids from functionalized precursors starts close to the sediment water interface soon after deposition of the organic matter due to the high reaction rates these low temperature reactions are independent of the geothermal regime within the limits of sample resolution of this study in contrast to this the depth of formation of diasterenes and spirosterenes is dependent on the geothermal gradient sedimentation rates indirectly determine through the effect of the resulting burial depth the age of the sediments in which these compounds first occur there is a significant effect of the geothermal gradient on most of the isomerisation reactions studied and it is most pronounced for the conversion of the 14 h b ring monoaromatic anthrasteroids to the 14 h isomers

hydrocarbon geochemistry of the puget sound region ii sedimentary diterpenoid steroid and triterpenoid hydrocarbons cyclic components of the aliphatic hydrocarbon mixtures extracted from puget sound sediment cores include a suite of c19 and c20 diterpenoid hydrocarbons of which fichtelite sandaracopimaradiene and isopimaradiene have been identified although apparently also derived from vascular plants these diterpenoid hydrocarbons have relative abundances distinctly different from the co existing plant wax n alkane suite five c27 c28 and c29 diasteranes and four c29 c30 and c31 17 h 21 h hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage these chromatographically resolved cycloalkanes along with the strongly covarying unresolved complex mixture have been introduced to puget sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill naturally occurring triterpenoid hydrocarbons including hop 22 29 ene diploptene are also present a new group of c30 polyenes has been detected which contains compounds apparently structurally related to a co existing bicyclic c25 diene and to c20 and c25 acyclic multibranched hydrocarbons described in a previous paper barrick et al 1980

organic geochemistry of marine sediments in antarctic region marine lipids in mcmurdo sound abstract the compositions of resolvable lipid components from four sediment cores 0 90 cm of mcmurdo sound ross sea have been examined the various lipid components occur in the following order of abundance sterols fatty acids n alcohols n alkanes pah the data indicate that the organic matter is mainly derived from recycled kerogen mixed with modern marine input the distribution of lipids and lignin analyses indicate that there is little recognizable higher plant debris in the sediments the sediments contain unaltered biogenic triterpenoids and there is no evidence for natural and or anthropogenic petroleum influx in the region aeolian transport of organic carbon from the continents appears to be negligible the dominance of labile alkenes c 25 compounds and hopenes and the presence of unsaturated fatty acids down to a depth of 90 cm reflect a very early diagenetic stage the persistent cold climate has probably helped in the better preservation of these labile lipids in the water column and in the young sediments diploptene 17 h 21 h hop 22 29 ene appeats to originate from autochthonous marine productivity in mcmurdo sound

origin and diagenetic transformations of c25 and c30 highly branched isoprenoid sulphur compounds further evidence for the formation of organically bound sulphur during early diagenesis abstract a number of c25 and c30 highly branched isoprenoid hbi sulphur compounds e g thiolanes 1 oxo thiolanes thiophenes and benzo b thiophenes with 2 6 10 14 tetramethyl 7 3 methylpentyl pentadecane and 2 6 10 14 18 pentamethyl 7 3 methylpentyl nonadecane carbon skeletons were identified in sediments ranging from holocene to upper cretaceous these identifications are based on mass spectral characterisation desulphurisation and in some cases by comparison of mass spectral and relative retention time data with those of authentic standards the presence of unsaturated c25 and c30 hbi thiolanes in a recent sediment from the black sea age 3 6 10 3 a strongly supports their formation during early diagenesis the co occurrence of hbi polyenes c25 and c30 and unsaturated hbi thiolanes c25 and c30 possessing two double bonds less than the corresponding hbi polyenes in this recent sediment testifies to the formation of unsaturated hbi thiolanes by a reaction of inorganic sulphur species with double bonds of the hbi polyenes furthermore a diagenetic scheme for hbi sulphur compounds is proposed based on the identification of hbi sulphur compounds in sediment samples with different maturity levels

free and sulphurized hopanoids and highly branched isoprenoids in immature lacustrine oil shales abstract a study of the solvent extracts of four samples from two immature oil shales from tertiary lacustrine basins ribesalbes and campins southern european rift system deposited under reducing conditions has allowed the identification of s containing hopanoids and novel highly branched isoprenoids hbi hbi derivatives occur only in the ribesalbes shales where two new structural types of c 25 s containing hbi isomers have been identified these compounds probably have different precursor organisms from those in recent marine systems they are present as thiophenes thiolanes and thiolane sulphoxides in one case and only as thiolanes in the other 17 21 h 17 21 h and 17 21 h thienyl and methylthienylhopanes have been found in the shales from the two basins in the campins samples these compounds occur together with thiolanyl and methylthiolanylhopanes distributions of 17 21 h and 17 21 h hopanes hop 17 21 enes and 2 methylhop 17 21 enes ribesalbes only are also encountered comparison of the hopane distributions from both solvent extractable aliphatic and thiophene fractions and the sulphur and oxygen bound macromolecular matter in ribesalbes basin shows a remarkable similarity between all fractions this resemblance points to rather uniform inputs and depositional processes for the accumulation of these compounds both as small molecules or bound to macromolecules e g early bonding of bacteriohopanepolyols to sulphur and to the macromolecular organic matter the good correlation among the macromolecular fractions in ribesalbes basin is reinforced when comparing the 13 c composition of phytane c 20 and c 25 hbi and the c 35 hopane homologues in the different fractions

geochemistry of c25 and c30 biogenic alkenes in sediments of the narragansett bay estuary abstract the distributions of a series of structurally related c 25 and c 30 biogenic alkenes in sediments of the narragansett bay estuary have been determined the suite of alkenes detected differs both quantitatively and qualitatively from those previously reported in other estuanne and coastal regions four c 25 mono and dienes and one c 30 diene comprise 73 91 of the total alkenes in all surface upper 2 5 5 cm sediments analyzed however significant geographic variations exist in the relative abundance of these five compounds throughout the estuary a comparison of alkene concentrations with 13 c of the bulk sedimentary organic matter has shown that the geographic variations of some alkenes reflect the distribution of marine organic matter suggesting a marine source for these compounds the distributions of other alkenes are not similarly correlated in particular concentrations of the c 30 diene are relatively constant and exhibit no dependence on the origin of organic matter in these sediments this distribution implies an in situ production of this alkene throughout the estuary analysis of several sediment cores reveals that alkene concentrations are generally highest at the surface and decrease to low constant values within the upper 25 cm an exception is the subsurface concentration of one c 25 diene which exhibits an increase at the same depth in two separate upper bay cores

the architecture of organic matter and its pores in highly mature gas shales of the lower silurian longmaxi formation in the upper yangtze platform south china the nanometer scale architecture of organic matter om and associated pores in highly mature gas shales from the lower silurian longmaxi formation in the upper yangtze platform of south china were investigated using field emission scanning electron microscopy sem focused ion beam sem and low pressure gas n2 and co2 adsorption bulk pore characterization the longmaxi shale comprises fine grained siliciclastic rocks deposited in a marine shelf environment which was dominated by quartz and clay minerals four porous om types were found in the longmaxi shale on the basis of the chemical composition and spatial occurrence of om including 1 isolated original om particles 2 om clay mineral complexes 3 om heavy mineral complexes and 4 secondary migrated bituminous om the pores in the particulate om are not homogeneously distributed and the processes leading to different pores depend on the specific om type the nature of om hosted pores is a result of several factors such as primary porous kerogen mechanical compaction organic inorganic interactions gaseous and liquid hydrocarbon generation retention and expulsion pore volumes and specific surface areas of the longmaxi shale derived from low pressure n2 and co2 adsorption experiments reveal positive linear relationships with total organic carbon contents which indicates that the pore systems in the highly mature longmaxi shale are dominated by om hosted pores additionally the om hosted pores appear connected compared to pores in the mineral matrix therefore the om hosted pore systems offer the preferential storage space and primary migration pathways for natural gas in the longmaxi shale reservoir

thermal stability of thiophene biomarkers as studied by hydrous pyrolysis abstract an immature r o 0 25 sulphur rich calcareous shale from the gessoso solfifera formation messinian in the vena del gesso basin northern italy was artificially matured by hydrous pyrolysis at constant temperatures ranging from 160 to 330 c for 72 h to study the applicability of alkylthiophenes as molecular indicators during progressive diagenesis and early catagenesis artificial maturation at temperatures up to 330 c generated large amounts of alkylthiophenes from the thermal degradation of kerogen the importance of the kerogen in the production of alkylthiophenes is supported by the observation that the isomer distributions of alkylthiophenes at high temperatures coincide with the isomer distributions of alkylthiophenes in the curie point pyrolysate of the isolated kerogen of the original sample the generation profiles of the thiophenes with a phytane carbon skeleton and the 3 4 di n alkylthiophenes suggest that continuous degradation of alkylthiophenes is also taking place so that the overall effect is alkylthiophene concentrations with intermediate values the structural isomer distribution of linear alkylthiophenes does not change significantly when these compounds are generated at different temperatures this implies that important information regarding the original positions of functionalities in the precursor molecules is retained and thus that alkylthiophenes are useful biomarkers at relatively high levels of thermal maturity up to r o 0 95 1 1

molecular evidence for basin scale photic zone euxinia in the permian zechstein sea abstract previous studies of maleimides 1 h pyrrole 2 5 diones oxidative degradation products of chlorophylls and bacteriochlorophylls and aromatic compounds derived from certain carotenoids i e isorenieratene indicate that photic zone euxinia pze occurred at least intermittently during deposition of the german kupferschiefer late permian however that work was restricted to a stratigraphic profile through the kupferschiefer of the lower rhine basin a shallow lagoon setting and it was not established if photic zone euxinia prevailed in the larger and deeper basins of the permian zechstein sea here we present maleimide and porphyrin distributions in sediments from the northern and southern permian basins in samples from both basins methyl iso butyl me i bu maleimide was recovered from the free extractable fraction and upon oxidation of vanadyl and nickel alkyl porphyrins on structural grounds me i bu maleimide derives ultimately from bacteriochlorophyll bchl c d or e and is thus indicative of the presence of green sulfur bacteria in the ancient zechstein sea consistent with this c 34 and c 35 porphyrins apparently derived from bacteriochlorophyll d were also identified in the northern basin samples because green sulfur bacteria require both light and free h 2 s these results indicate that photic zone euxinia occurred at least periodically during the early history of the zechstein sea

a novel c35 highly branched isoprenoid polyene in recent indian ocean sediments a novel c35 7 highly branched isoprenoid hbi alkene has been identified in extracts of surface sediment samples from the indian ocean by isolation followed by characterization by gc ms and hydrogenation this polyunsaturated compound might be derived from diatoms

hydrocarbons of the hypersaline basins of shark bay western australia shark bay is an 8000 sq km shallow marine embayment on the western coast of western australia the waters exhibit a well established salinity gradient from oceanic to hypersaline the chemical assemblage of sediment hydrocarbons along the salinity gradient may be classified into two distinct chemogeographic types firstly oceanic sediments contain n alkanes and a suite of highly branched and branched cyclic c25 alkenes hypersaline sediments are characterised by a high relative abundance of a c25h50 alkene together with an analogous c20h40 alkene and its parent c20h42 alkene 2 6 10 trimethyl 7 3 methylbutyl dodecane a pair of alkanes c21h42 and c22h44 increase in concentration and relative abundance with depth the hydrocarbons of the hypersaline basins are found in only trace amounts in oceanic sediments these chemical signals are overlain by further input indicative of the immediate biotic community

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

earth science gas hydrates and deglaciations long ago earth experienced a series of especially severe glaciations a new explanation for deposits laid down at the end of these events centres on the large scale release of methane from solid gas hydrates

evidence for sulphide links in a crude oil asphaltene and kerogens from reductive cleavage by lithium in ethylamine abstract reduction of a sulphur rich asphaltene from a crude oil rozel point with lithium in ethylamine li etnh2 affords an alkane fraction similar to that obtained from desulphurisation with raney nickel but in higher yield using li etnd2 deuterium labelled alkanes were obtained thereby confirming the presence of sulphide linkages in the asphaltene fraction reduction of two sulphur rich kerogens with similar sulphur contents serpiano shale m triassic and jurf ed darawish jed u cretaceous afforded significant quantities of polar solvent extractable material both kerogens also yielded low amounts of hydrocarbons although the amount released from jed kerogen was significantly higher the results indicate that whereas the kerogens contain hydrocarbon moieties intermolecularly linked by sulphide bridges the distributions of the precursors lipids which were incorporated were different for example gc ms analysis of the labelled products from jed kerogen revealed them to be dominated by steranes of algal origin with the position s of deuterium labelling providing evidence of sulphide linking and cross linking on the other hand the labelled products from serpiano kerogen were dominated by hopanes of bacterial origin which were linked terminally via the side chain

authigenic mineralizations at unconformities implication for reservoir characteristics abstract scanning electron microscopy coupled with petrographic and reservoir characteristic measurements were carried out on 447 core samples from seven different boreholes penetrating concealed unconformities they include cretaceous devonian lower lias rhaeto liassic unknown age carboniferous limestone series triassic lower carboniferous triassic upper coal measures triassic permo trias permian and multiple unconformities from the middle east western desert iraq reservoir characteristics at unconformities have been adversely affected by the development of authigenic minerals formed by the mixing of formation waters with infiltrated acidic waters into the paleo surfaces followed by extensive marine incursions and invasion of alkaline waters the result is the formation of complex authigenic minerals in the form of overgrowths of quartz and rhombic feldspars accompanied by clay mineral neoformations as pore fillings and coatings in the form of kaolinite illite mixed layered illite smectites and to a lesser extent chlorites the final elimination of porosity was achieved by late diagenetic calcite colomite and sometimes gypsum cementation

organic matter and lipids in sediments of lake bled nw slovenia source and effect of anoxic and oxic depositional regimes sources of organic matter om and lipids were assessed and factors affecting om degradation were studied for two sediment cores representing distinct depositional regimes i e the oscillating oxic to suboxic anoxic western basin and oxic zaka bay for eutrophic lake bled nw slovenia lower surface organic carbon oc concentration was determined in the western basin than for zaka bay sediments 5 1 vs 5 4 wt dry sediment respectively but one order of magnitude greater total lipid concentration was observed in the former also there was a higher proportion of autochthonous om in the western basin 77 vs 66 on the basis of atomic c n ratios lipid based origin assessment suggested a similar contribution of autochthonous om in the western basin 64 77 but a lower one in zaka bay 50 it seems that redox potential is the main factor governing om degradation in the western basin in contrast a contribution from more refractory terrestrial om via the surface inflow in zaka bay and higher sedimentation rates may surpass redox effects in zaka bay overall oxygen may play a more important role in degradation of the more labile pool i e lipids than bulk om higher apparent degradation rate constants k for lipids also suggested a greater lability than for oc while respective k values were higher in the oxic than anoxic environment

isotopically heavy carbon in the c21 to c25 regular isoprenoids in halite rich deposits from the sdom formation dead sea basin israel abstract a series of miocene pliocene halite deposits with extremely low organic carbon contents from the sdom formation dead sea basin israel have been studied distributions and 13c contents of biomarkers have been determined using gc ms and irm gcms analyses respectively the hydrocarbon fractions consist mainly of pristane phytane and c21 to c25 regular isoprenoids the predominance of c21 regular isoprenoids in the dead sea halites and other hypersaline deposits indicate that these components could be derived from ether bound membrane lipids of halophilic archaea the lack of intact ether bound lipids in the polar fractions indirectly infers that such components have already been released at early stages of diagenesis their 13c contents are enriched in 13c by up to 7 compared to the biomarkers of presumed phytoplanktonic origin i e steranes and hopanes within the same sediment sample in agreement with a source other than algae and cyanobacteria thus tentatively assigned as halophilic archaea based on biomarker distributions 13c contents and mineral compositions these sediments appear to have been deposited in a salinity stratified water body with a bottom water brine continual evaporation and deposition of the higher salts i e carnallites are favourable conditions for the growth of halophilic archaeal communities

rapid sulfurisation of highly branched isoprenoid hbi alkenes in sulfidic holocene sediments from ellis fjord antarctica samples of particulate organic matter from the water column and anoxic holocene sediment layers from the small meromictic basin smb in ellis fjord eastern antarctica were analyzed to study the early incorporation of reduced inorganic sulfur species into highly branched isoprenoid hbi alkenes hbis were not detected in the water column samples taken during austral winter whereas compounds containing the c25 hbi skeleton were abundant in all analyzed holocene sediment layers the structure of the c25 2 hbi alkene and its enriched stable carbon isotopic composition suggest that it is produced by a diatom or diatoms probably belonging to the navicula genus in the sea ice which covers the area most of the year within just 500 years of deposition all of the hbi alkene was sulfurised a mixture of products was formed including components tentatively identified as a c25 hbi thiane and three s containing dimers composed of two c25 1 hbi skeletons linked together by a sulfide bond most was however converted to polar s containing compounds the reaction rate for sulfurisation of the c25 2 hbi alkene is the highest observed so far in natural systems sterols and other lipids known to be prone to sulfurisation were not sulfurised the reason for this is unclear

identification and occurrence of novel c36 c54 3 4 dialkylthiophenes with an unusual carbon skeleton in immature sediments abstract a series of novel long chain 3 4 dialkylthiophenes c36 c54 was identified in a number of sediments ranging from pleistocene to cretaceous the identifications were based on mass spectral characterisation desulphurisation and mass spectral data of synthesised model compounds these organic sulphur compounds are probably formed by sulphur incorporation into mid chain dimethylalkadienes with two methylenic double bonds these putative precursor lipids are unprecedented and may be considered rather unusual the distribution of 3 4 dialkylthiophenes in sediments varies considerably with the depositional palaeoenvironment indicating that these compounds have a potential as molecular markers reflecting changes in palaeoenvironment

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

aryl isoprenoids and diaromatic carotenoids in paleozoic source rocks and oils from the western canada and williston basins abstract aryl isoprenoids in the range c13 c31 have been identified in source rock bitumens and oils from several paleozoic age petroleum systems in the western canada and williston basins the principal compounds possess the 2 alkyl 1 3 4 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria two c40 perhydrodiaromatic carotenoids which are structurally related to the presumed precursors of the aryl isoprenoids have also been identified in oils and source rock bitumens of the duvernay late devonian petroleum system pyrolysis gas chromatograms of kerogens isolated from several paleozoic source rocks show an unusual abundance of 1 2 3 4 tetramethylbenzene it is proposed that this compound arises from cleavage of diaromatic carotenoid moieties which have been incorporated into the kerogen structure with increasing maturation concentrations of the aryl isoprenoids in duvernay source rock bitumens increase to a point whereas the c40 perhydrodiaromatic carotenoids decrease steadily previous studies have suggested that aryl isoprenoids may be indicators of enhanced salinity environments this is not supported by the present work which shows high concentrations in source rocks associated with presumed normal marine salinities there is however a general association with intervals of condensed clastic or mixed clastic carbonate sedimentation within carbonate depositional systems from the association found and from parallels to modern habitats of photosynthetic bacteria it can be inferred that these biomarkers indicate prolific bacterial growth in a stratified water column at and below the oxic anoxic boundary layer in sub tropical to tropical marine environments

organic carbon as a palaeoenvironmental indicator in the marine realm recent developments in biogeochemistry have made accessible all information currently known to be present in sedimentary organic compounds i e the carbon skeleton structure the positions of functional groups and stable carbon isotope ratios this combined information has strengthened the applications of sedimentary organic compounds as biomarkers and palaeoenvironmental indicators this review summarizes the most important biomarkers and their applications in reconstructing marine palaeoenvironments and processes the marine environment is characterized by the combined presence of specific compounds such as organic sulphur compounds dinosteroids 24 n propylsteroids even in trace amounts high amounts of c hbi hydrocarbons and the absence of long chain n alkanes with odd over even predominance bicadinanes and specific higher plant triterpenoids e g oleanane furthermore palaeoenvironmental conditions such as photic zone anoxia hypersalinity microbial sulphate reducing activity algal blooming palaeo upwelling and palaeo surface seawater temperature are indicated by molecular and or isotopic characteristics biomarkers from terrestrial sources are included because land derived organic matter is an important contributor to coastal and shallow marine environments a short case study within a holocene terrestrial marine setting florida bay usa is also presented to illustrate the reconstruction of transgressive regressive trends using selected organic compounds

diatom biomarkers during the eocene oligocene transition in the il pinskii peninsula kamchatka russia abstract marine strata of the il pinskii section northeastern kamchatka russia expose the complete eocene oligocene e o succession although diatom fossils are very poorly preserved in these mudstones and carbonate concretions oligocene mudstones contain typical diatom biomarkers the c 25 highly branched isoprenoids hbis in concentrations that rise markedly above the e o boundary the abundance of the dinoflagellate biomarkers known as dinosteranes decreases through the late eocene to oligocene interval a rise in the abundance of hbis through this time interval suggests that the post e o diatom community of the northwest pacific region was dominated by the genus rhizosolenia hbis in sedimentary rocks spanning the e o transition may show the appearance of the oligocene marine diatom rhizosolenia oligocaenica and may therefore be useful as biomarkers in regional biostratigraphic correlation of the northwest pacific during this interval an e o boundary in the il pinskii section is proposed based on hbi distribution