a molecular organic carbon isotope record of miocene climate changes the difference in carbon 13 13c contents of hopane and sterane biomarkers in the monterey formation naples beach california parallels the miocene inorganic record of the change in 18o 18o reflecting the miocene evolution from a well mixed to a highly stratified photic zone upper 100 meters in the pacific steranes 13c 25 4 0 7 per mil versus the pee dee belemnite standard from shallow photic zone organisms do not change isotopically throughout the miocene in contrast sulfur bound c35 hopanes likely derived from bacterial plankton living at the base of the photic zone have systematically decreasing 13c concentrations in middle and late miocene samples 13c 29 5 to 31 5 per mil consistent with the middle miocene formation of a carbon dioxide rich cold water mass at the base of the photic zone

sulphur and oxygen sequestration of n c37 and n c38 unsaturated ketones in an immature kerogen and the release of their carbon skeletons during early stages of thermal maturation sedimentary rock from the gessoso solfifera formation messinian in the vena del gesso basin northern italy containing immature ro 0 25 s rich organic matter was artificially matured by hydrous pyrolysis at temperatures from 160 to 330 c for 72 h to study the diagenetic fate of n c37 and n c38 di and tri unsaturated methyl and ethyl ketones alkenones biosynthesised by several prymnesiophyte algae during early diagenesis the alkenones are incorporated into the kerogen by both sulphur and oxygen cross linking as indicated by chemical degradation experiments with the kerogen of the unheated sample heating at temperatures between 160 and 260 c which still represents early stages of thermal maturation produces large amounts up to 1 mg g toc of s bound o bound and both s and o bound n c37 and n c38 skeletons saturated n c37 and n c38 methyl ethyl and mid chain ketones c37 and c38 mid chain 2 5 di n alkylthiophenes c37 and c38 1 2 di n alkylbenzenes and c37 and c38 n alkanes with increasing thermal maturation three forms of the n c37 and n c38 skeletons are relatively stable saturated hydrocarbons 1 2 di n alkylbenzenes and saturated ketones whereas the s and o bound skeletons are relatively labile these results suggest that in natural situations saturated ketones with an n c37 and n c38 skeleton can be expected as well as the corresponding hydrocarbons

osl chronology of sand deposits and climate change of last 18 ka in gurbantunggut desert northwest china the development of the gurbantunggut desert is mainly controlled by the westerly wind and at present has little influence from indian and southeast asian monsoons a combined study using optically stimulated luminescence osl dating ground penetrating radar gpr surveys and climatic proxies analysis was carried out in the southern part of the desert the chronology extends back to 18 ka and is constructed based on 16 osl ages from boreholes in the linear dune body and the inter dune area the chronology suggests that sand deposition in the last 18 ka experienced two rapid accumulation phases at 11 and 2 5 ka ago which were also evident from the gpr surveys these periods relate to increased aridity in the region five climate phases are identified from the last 18 ka based on the osl chronology and climatic proxy analysis with grain size and magnetic susceptibility measurements the deglacial period 18 3 10 4 ka is characterized by climate instability and possible glacial melting events the holocene optimum peaked 8 5 ka and terminated 3 6 ka ago when the regional climate became arid osl samples from the dune body cluster around 2 5 ka which indicates rapid advance extension of dune bodies at this time copyright 2011 john wiley sons ltd

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

methane derived carbonate conduits from the late aptian of salinac marne bleues vocontian basin france petrology and biosignatures abstract peculiar carbonate bodies occur in distinct marl layers of the marnes bleues formation aptian albian vocontian basin southern france the carbonate conduits exhibit pipe or sausage like forms and a central channel their sizes range between 30 and 60 cm in length and 5 10 cm in diameter the conduit carbonates consist of automicrite authigenically formed within the sediment millimeter sized aggregates of framboidal pyrite are abundant within the conduit automicrites probably representing former colonies of sulfate reducing bacteria the central channel reflects former pathways of reduced fluids in the carbonate conduit ni enrichments at the margins of the central cavity are may be due to the activity of methane related metabolism as ni is an important bio element for respective microbes light stable carbon isotope ratios of the conduit automicrites 25 86 to 23 10 vpdb point to carbonate precipitation linked to anaerobic oxidation of methane aom while less depleted stable carbon isotope ratios of microspar in marginal zones of the central opening 8 96 vpdb are in line with microbial sulfate reduction a methane related origin of the conduit carbonates is confirmed by the presence of authigenic lipid biomarkers tentatively sourced by archaea most of which are characterized by strong 13 c depletions 13 c values down to 104 the presence of organically bound sulfur is well in line with microbial sulfate reduction isorenieratane potentially point to the presence of brown pigmented green sulfur bacteria the methane was probably sourced by older oae black shales which are known to contain isotopically 13 c heavy biomarkers of archaea as reported elsewhere

a high resolution historical record of holocene anoxygenic primary production in the black sea i reconstruct the historical record of anoxygenic primary production in the black sea over the last 8200 years by an analysis of chlorobium carotenoids in sediments anoxygenic photosynthesis in the black sea occurs only when hydrogen sulfide containing deep water penetrates the euphotic zone the data show that the black sea has experienced large fluctuations in the extent of anoxygenic primary production and therefore the depth of the h2s chemocline throughout much of the holocene changes in the depth of the h2s chemocline also shift the dominant phytoplankton populations in the water column to noncarbonate bearing species and result in the formation of intense dark bands in sediments

latitudinal change of normal paraffin composition in the northwest pacific sediments abstract we analyzed normal saturated paraffins n paraffins in 70 surface sediments in the northwest pacific to examine the spatial distribution of organic materials all sediments show bimodal n paraffin abundance patterns against carbon number with maxima at c 16 and c 31 indicating that n paraffins in marine sediments are a mixture of long chain n paraffins from land based higher plant waxes and short ones from marine organisms we observed in this study a significant change of carbon preference index cpi from 2 5 in low latitudes to 4 5 in mid high latitudes around 19 25 n the following influences are discussed as the cause of cpi offset between low and mid high latitudes 1 meteorological conditions 2 n paraffin composition of higher land plants 3 contribution of petroleum components and 4 mixing ratio of higher land plants and marine organisms however none of them can be the possible cause of the cpi offset because n paraffin content and composition vary significantly according to the species of a bacterium difference of the species of bacterial communities between low and mid high latitudes may be a possible reason for the cpi offset found in sediment from the northwest pacific

a discontinuous climatic record from 187 to 74 ka from a speleothem of the clamouse cave south of france this study presents a continental paleoclimatic record in the south of france based on n 18 o n 13 c and the 234 u 238 u activity ratio dated by the 230 th 234 u disequilibrium method with thermal ionization mass spectrometry a stalagmite cla4 from the clamouse cave offers a discontinuous stable isotopic record between 189 ka and 74 ka which covers marine isotope stages mis 7 6 4 5 5 5 3 and 5 1 the growth phases of the cla4 stalagmite correspond to high sea level stages except during mis 6 4 169 162 ka all the growth phases of cla4 correspond to humid periods corresponding to the sapropel events observed in the eastern mediterranean basin thus the influence of a strong hydrological activity in the eastern mediterranean basin during these periods prevailed as far west as the south of france because the karstic system studied strongly buffers the isotopic composition of water isotopic variations of the calcite deposited in the cave represent mainly global and large scale environmental variations when isotopic equilibrium conditions prevailed for calcite crystallization sub stage 5 3 the end of 5 5 and mis 7 were colder by about 4 6 c calculated temperature compared to present day temperature while the growth phases of substages 5 1 and the beginning of 5 5 reflect environmental conditions close to present ones the n 18 o and n 13 c values of cave deposits of the sub stage 6 4 are 1 strongly marked by kinetic fractionation processes such as evaporation due to moisture deficit within the cave atmosphere during the first step of this growth phase and 2 related to higher humidity due to a second period of enhanced rainfall during the second step of growth this study shows that even if calcite has not been deposited at isotopic equilibrium its isotopic composition can give insights into the environmental conditions at the time of deposition 2002 elsevier science b v all rights reserved

molecular indicators for palaeoenvironmental change in a messinian evaporitic sequence vena del gesso italy i variations in extractable organic matter of ten cyclically deposited marl beds abstract a screening by direct desulphurization of extracts was employed for 21 immature organic sulphur rich marl samples from 10 of the 14 evaporite cycles in an italian messinian evaporitic basin vena del gesso gessoso solfifera fm the combined information retrieved from free and sulphur bound carbon skeletons enabled a detailed palaeoenvironmental reconstruction the biomarker compositions of the marls point to large variations in the composition of species in the water column e g dinoflagellates diatoms and other algae cyanobacteria methanogens green sulphur bacteria and bacterivorous ciliates and in contributions from the continent i e land plants within each marl bed and between marl beds the marl beds were deposited within a stratified lagoon where anoxic conditions extended into the photic zone for much of the time

geochemical study of macromolecular organic matter from sulfur rich sediments of evaporitic origin messinian of sicily by chemical degradations abstract selective chemical degradations have been performed on sulfur rich macromolecular organic matter from sediments of the messinian of sicily upper miocene italy the biomarkers released upon different desulfurization experiments are much more abundant than the free lipids and display completely different distributions which reflect the selective trapping of poly functionalized molecules by inorganic sulfur species at an early stage of diagenesis the bound biomarker distributions reveal a dominant phytoplanktonic input originating from an upper oxic water layer and a moderate bacterial reworking of the organic matter a contribution from cyanobacteria to the organic matter cannot be excluded the presence of carotenoids typical from photosynthetic sulfur bacteria attests to a stratified water body where an anoxic photic zone occurred lialh4 hydrogenolysis of sulfur rich macromolecules revealed that polysulfide bridges contribute to a large extent in the cross linking the results of deuterium labelling experiments are discussed in terms of sulfur incorporation on functionalized lipids

the deep water counterpart of the messinian lower evaporites in the apennine foredeep the fanantello section northern apennines italy abstract a possible deep water non evaporitic unit equivalent of the messinian lower evaporites has been recognised in the northern apennine foredeep this unit whose existence is implicitly admitted in the two step model of the mediterranean messinian salinity crisis is documented here for the first time it occurs throughout the apennine foredeep basin below a thick horizon of resedimented gypsum deposits usually ascribed to the lower evaporites actually the lower evaporites of the apennine foredeep basin include both shallow water in situ precipitated facies and deep water resedimented facies deposited in distinct depocenters the usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a physical stratigraphic considerations about the downbasin correlation of the messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre evaporitic successions underlying the in situ precipitated evaporites in this work a multidisciplinary study has been carried out on a 140 m thick composite section fanantello section to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits the topmost part of the section comprises a 60 m thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a the complete disappearance of foraminifera b the occurrence of high salinity tolerant thecosomatous pteropods creseis sp c the abundance peaks of the calcareous nannofossil sphenolithus abies interpreted as related to highly stressed likely hyperhaline conditions d the appearance of hyperhaline and or stratified water molecular indicators gammacerane based on a multidisciplinary integrated stratigraphic approach this barren interval is here proposed to be a deeper water time equivalent of the in situ primary lower evaporites thus allowing to assess the events connected to the onset and the first phase of the messinian salinity crisis from a basinal perspective these data lend support to the hypothesis that the resedimented evaporite deposits of the apennine foredeep basin postdate the in situ evaporites thus implying that the term lower evaporites actually comprises rock bodies with different origins and separated in time and space by the messinian erosional surface and its correlative conformity this could be true also for other mediterranean basins where the stratigraphy of deep water successions should be carefully re examined

product distributions from chemical degradation of kerogens from a marl from a miocene evaporitic sequence vena del gesso n italy abstract lithium in ethylamine li etnh 2 treatment has been carried out on sulphur rich kerogens from 10 sub samples of the cycle iv marl from the vena del gesso evaporitic sediments upper miocene italy the treatment releases after chromatography of the resulting solvent extracts up to 30 of the kerogen total organic carbon the biomarkers released are dominated by components of algal origin the concentrations of the aliphatic hydrocarbons obtained are of the same order of magnitude as the bound alkanes released upon desulphurization of polar fractions from organic extracts and show similar distributions the presence of diaromatic isoprenoids derived from chlorobiaceae indicates that photic zone anoxia occurred during the deposition of the cycle iv marl such conditions being more prevalent at the middle of the section polar material makes up by far most of the organic material released and contains in particular alcohols and amides which may result from the cleavage of ester bonds present in these immature kerogens the amides being secondary products formed by reaction with the etnh2 in the case of the alcohols however these components could also arise from cleavage of sulphide bound moieties

reconstructing the palaeoecosystem and palaeodepositional environment within the upper devonian lower mississippian bakken formation a biomarker approach abstract biomarkers have been used extensively to correlate oil families oil source rock relationships and source inputs and to help identify the palaeodepositional environment for a given geological sedimentary unit despite their application in characterising the bakken formation shales a number of biomarkers still appear unable to provide us a consistent understanding regarding heterogeneity in source organic matter and palaeoenvironment here we infer the palaeodepositional environment within the bakken formation shales using a biomarker suite and biomarker depth profiles we also use the occurrence and abundance of biomarkers to define organic facies and to make inferences regarding biotic interactions drawn from modern analogues the variations and co occurrence of biomarkers is explained by the existence of a proposed complex algal bacterium bacteriovore palaeoecosystem this approach not only helps explain the depth variation in occurrence and concentration of biomarkers and the molecular composition of associated organic matter but also advances the use of biomarker analysis and biomarker associations to determine a complex environment sensitive palaeoecosystem

the primary lower gypsum in the mediterranean a new facies interpretation for the first stage of the messinian salinity crisis abstract the detailed facies and physical stratigraphic analysis of the primary lower gypsum in the mediterranean indicates a surprising bed by bed correlation at basin scale spain italy hellenic arc and cyprus arc that is tuned to the orbital calibration for the first stage of the messinian salinity crisis from 5 96 to 5 61 ma ago a total of 16 precessionally controlled gypsum cycles were deposited rapidly in less than 350 ka forming sequences up to 300 m thick the lack of subaerial exposure features and the common facies associations and stacking pattern for sections located thousands of kilometers apart in different geological settings indicates a modest depositional depth not extremely shallow selenite deposition occurred only at the bottom of restricted marginal basins less than 200 m deep while no gypsum could precipitate in the deeper euxinic mediterranean portions where only thin and barren shale dolostone couplets formed the lowermost selenite beds pass laterally to dolomite rich limestones interbedded with barren euxinic shales in poorly oxygenated settings indicating that the gypsum sedimentation was diachronous and did not necessarily mark the onset on the messinian salinity crisis evaporite facies sequences ef1 to 8 within individual gypsum beds show small scale subaqueous sedimentary cycles that mimic regressive transgressive cycles a initial evaporite precipitation at relatively low supersaturation produced the massive selenite facies ef3 in a relatively deep setting b continuous evaporation and drawdown by oscillating brine level formed the banded selenite ef4 at the aridity acme of the precessionally controlled cycle c general progressive brine level rise with strong brine flow led to the formation of large selenite supercones branching laterally supercones in spain and branching selenite ef5 in the rest of the mediterranean and d flooding by undersaturated continental water terminated gypsum precipitation with the deposition of argillaceous sediments ef1 northern apennines and or limestone ef2 sicily and spain during the humid phase in the precession climate cycle the stacking pattern and selenite facies associations suggest an overall shallowing upward trend with a basin wide hydrologic change starting from the 6th cycle 5 84 ma which is marked by the appearance of the branching selenite facies supercones in spain and indicates that the brines became current dominated the sr isotope stratigraphy suggests that in the northern apennines the brines were strongly modified by continental waters 87 sr 86 sr 0 708893 to 0 708998 and received direct pulses of atlantic seawater 87 sr 86 sr 0 70900 to 0 709024 only in the upper part of the section in areas away from the mainland such as sicily the continental input was by far less important

variations in origin and composition of kerogen constituents as revealed by analytical pyrolysis of immature kerogens before and after desulphurization abstract kerogens isolated from nine samples from a single marl bed of the gessoso solfifera formation in the vena del gesso basin upper miocene italy were treated with crcl 2 and li etnh 2 to remove inorganic and organic sulphur respectively the untreated and desulphurized crcl 2 and li etnh 2 kerogens were qualitatively and quantitatively analyzed by flash pyrolysis gas chromatography mass spectrometry typically significant variations in the relative contributions and abundances of n alk 1 enes n alkanes alkylated pyrroles thiophenes and supposedly s bound moieties released as phytenes and sterenes were observed the first series of products n hydrocarbons contributed relatively more to the pyrolyzates of the desulphurized kerogens suggesting an enrichment of microalgal derived aliphatic macromolecules these marine micro organisms are thought to belong in part to the class of eustigmatophyceae alkylated pyrroles were barely detectable in the untreated kerogen pyrolyzates whereas they contributed significantly to those from the treated kerogens similar treatment of a porphyrin octaethylporphyrin revealed that alkyl porphyrins are thermally too stable to be cleaved upon pyrolysis however li etnh 2 treatment reduced the porphyrin standard such that it could generate mainly monopyrroles upon pyrolysis it is concluded that li etnh 2 treatment reduced tetrapyrrole moieties bound to the desulphurized kerogen network

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

how dry was the mediterranean during the messinian salinity crisis the messinian salinity crisis msc 5 97 5 33 ma is an enigmatic episode of paleoceanographic change when kilometers thick evaporite units were deposited in the mediterranean basin it is generally accepted that during the msc interval there was a dry climate in the mediterranean region it is difficult to assess how dry the climate was during the msc because a modern analogue in size and duration is absent here we reconstruct hydrological changes in the mediterranean basin during the three main msc stages using excellently preserved biomarkers we used the hydrogen isotopic composition of the long chain n alkanes dn alkanes to reconstruct the hydrological changes on the land adjacent to the mediterranean sea additionally the d of long chain alkenones dalkenones is used to observe changes in the mediterranean sea water source the dn alkanes recorded during the deposition of primary lower gypsum stage 1 in monte tondo indicate a d of the precipitation comparable to the present day mediterranean implying a similar hydrologic regime indicated by experiments modelling the miocene pliocene transition elevated dalkenones values from halite unit stage 2 of the realmonte mine are associated with kainite and giant polygons consistent with presumably high evaporative conditions during halite deposition the dn alkanes recorded during the deposition of upper gypsum stage 3 in eraclea minoa indicate a dprecipitation typical for much drier settings similar to the red sea region the relative contribution of the different alkenones from eraclea minoa is similar to the one observed in present day marine settings suggesting that during stage 3 connections to the open ocean were likely maintained however the dalkenones records during deposition of the evaporites in eraclea minoa are similar to those synchronously registered in the black sea implying that a similar hydrologic regime characterized by extended drought covered large areas of southeastern europe based on the dalkenones similarity and the paratethys type of lago mare fauna in the mediterranean we speculate that the surface water during stage 3 was at times derived from the black sea

recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach study of organic matter in immature sediments from a messinian evaporitic basin shows that consideration of structures modes of occurrence and carbon isotopic compositions of free and sulfur bound carbon skeletons allow identification of biochemical precursors detailed information concerning biotic communities present during deposition of sediments can be retrieved in this way moreover unprecedented biochemicals were recognized these extend the horizon of biomarker geochemistry

distributions of pigments in the organic matter of marls from the vena del gesso evaporitic sequence abstract the porphyrins and carotenoids of marl horizons within the messinian evaporitic cycles of the vena del gesso basin show variations in abundance and composition throughout a sequence of ten cycles significant variations are also apparent within individual marl horizons the differences in pigment distribution reflect significant changes in the environmental conditions during sediment deposition the presence of significant amounts of isorenieratene and co occurrence of an alkyl porphyrin with a c 34 skeleton provide evidence for anoxic conditions extending into the photic zone of the palaeo water column variations in the free pigment contents of the marls reflect a regressive trend both during deposition of an individual marl and over the entire sequence

stepwise chemical degradation of immature s rich kerogens from vena del gesso italy stepwise chemical degradation involving cleavage of ester bonds koh meoh sulfide and remaining ester bonds li etnh2 ether bonds hi lialh4 and sub units linked to aromatic moieties ruo4 has been carried out on the kerogens of two immature sulfur rich marls iv 1 4 and 1 8 toc ca 1 5 from evaporitic cycle iv of the gesosso solfifera formation messinian vena del gesso italy up to 80 of the organic matter was converted to solvent soluble material with the greatest proportion released by li etnh2 the majority by far of the extracts comprises polar macromolecular material which is thought to correspond to high molecular weight sub units of the kerogen quantification of the small amounts 1 of the released gc amenable components indicates that diagenetic sulfurization was more important in the case of kerogen iv 1 4 but that the extent of oxygen sequestration was similar in both cases the distributions of biomarkers released by ether cleavage of the desulfurized residue and polar fraction showed differences which reveal heterogeneity in the building blocks making up different macromolecular fractions

geochemical characterization of malm zeta laminated carbonates from the franconian alb sw germany ii abstract during jurassic times especially within the malm stage local depressions formed on the eastern bavarian carbonate platform that were surrounded by wall reefs this created a unique depositional environment where in an open marine setting stagnant and anoxic bottom waters developed in an intra reef depression anoxic conditions were stabilized below wave base by enhanced salinity in the bottom waters and establishment of a density stratification biomarker analysis was applied to characterize palaeosalinity and redox conditions utilizing organic sulfur compound methylated chroman hopanoid and saturated isoprenoid distributions prevention of terrigenous influx by protecting reef walls lead to iron deficiency in intra reefal sediments causing early diagenetic sulfurization of functionalized lipids absence of clay mineral catalysts and early sulfurization favored an unusual steroid distribution lacking rearranged analogues but providing coexistence of saturated steranes with and configuration 13 17 spirosterenes unknown sterenes and steradienes as well as mono di and triaromatic steroids desulfurization of the polar fraction was carried out for two samples to verify that palaeoenvironment reconstruction based on free hydrocarbon and heterocompound distribution was not invalidated by sulfur quenching of selected compounds gammacerane was found to be the only component to occur exclusively in the sulfur bound fraction only minor amounts of hydrocarbons were released upon desulfurization implying that free bitumen analysis was applicable for organofacies characterization organic petrological investigation of organic mats revealed the presence of two different types of such structures comparison of organoclast fluorescence spectra with those of extracted porphyrin fractions indicate an origin of porphyrins exclusively from cyanobacterial mats whereas algal dominated mats yield no porphyrins this aims towards a better localization of specific biomarker origin in geological samples

molecular isotopic evidence of environmental and ecological changes across the cenomanian turonian boundary in the levant platform of central jordan abstract we evaluated the structure of planktonic communities and paleoenvironmental conditions throughout the cenomanian turonian oceanic anoxic event oae2 by studying bulk geochemical properties and the molecular isotopic composition of source specific hydrocarbons from organic rich sediments deposited in an intrashelf basin at the levant platform central jordan high concentrations of desmethyl and 4 methylsteranes as well as dinosteranes indicate that marine algae including dinoflagellates were the main primary producing organisms the presence of 2 methylhopanes and 13 c enriched hopanes in addition to isotopically enriched aryl isoprenoids evidenced the contribution of cyanobacteria and green sulfur bacteria respectively additionally variable but fairly low 15 n values during oae2 suggest the occurrence of diazotrophy as a likely important process fueling primary production during oae2 in this stratified anoxic continental platform variations in the relative contribution of biomarkers revealed changes in planktonic communities associated with sea level change and water column stratification oae2 was characterized by strong stratification anoxic bottom waters and a deep chemocline as evidenced by high gammacerane and homohopane indices and the absence of photic zone euxinia pze markers respectively however the presence of isorenieratane and its derivatives in post oae black shales points to a shoaling of the chemocline and to pze this interval was also characterized by an exceptionally high abundance of chlorophyll derived pristane and phytane up to 2 mg g 1 toc likely as a result of highly enhanced primary production and organic matter preservation remarkably this high productivity event co occurs with an exceptionally high abundance of calcispheres reported elsewhere to be part of a global bio event

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

dinosterane and other steroidal hydrocarbons of dinoflagellate origin in sediments and petroleum abstract the steroidal alkanes of a selection of sediments and oils have been examined by gc ms with multiple metastable reaction monitoring specific 4 methyl sterane isomers have been identified by comparison with isomers synthesized from sterols isolated from dinoflagellates an immature marine oil shale and two mature marine oils of triassic to early cretaceous age contained high concentrations of c30 steranes comprising desmethyl 24 ethyl 4 methylcholestane and 4 23 24 trimethylcholestane dinosterane isomers an immature non marine oil shale and two non marine oils of cretaceous to eocene age contained stereoisomers of 24 ethyl 4 methylcholestane as the dominant c30 steranes reaction monitoring analyses in gc ms are particularly suited to unravelling complex distributions of homologous and stereoisomeric steroids encountered in oils and their source rocks

flocculent layers and bacterial mats in the mudstone interbeds of the primary lower gypsum unit tertiary piedmont basin nw italy archives of palaeoenvironmental changes during the messinian salinity crisis abstract the recognition of peculiar laminated layers atypically rich in a biogenic intrabasinal component in the mudstone intervals from the messinian late miocene primary lower gypsum unit 5 97 5 60 ma of the piedmont basin nw italy provides information on the palaeoenvironmental evolution at precessional insolation maxima these cyclic layers consist of irregular alternation of cm thick grey terrigenous laminae and whitish composite packets the latter is in turn composed of sub mm thick wrinkled dolomite rich laminae that alternate with terrigenous ones two types of layers can be distinguished i peloidal layers composed of faecal pellets and irregular diatom rich aggregates interpreted as marine snow floccules and ii filament bearing layers composed of interwoven filaments up to 150 m across corresponding to remains of beggiatoa like giant sulphide oxidising bacteria by comparison with present day settings the peloidal layers are interpreted as flocculent layers deposited on anoxic sea bottoms following episodes of phytoplankton bloom in the upper water column the filament bearing layers are considered as chemotrophic microbial mats growing on dysaerobic sea bottoms the uncommon preservation of both kinds of layers is the result of extensive dolomite precipitation in the shallow subsurface induced by bacterial sulphate reduction the laminated layers are the first reported example of a high frequency climate driven cyclicity in the non evaporitic portion of the primary lower gypsum unit their stacking pattern within the mudstone intervals reflects the gradual increase of the oxygen content of bottom waters during the humid precessional hemicycle culminating with gypsum deposition at the onset of the arid phase

molecular indicators for palaeoenvironmental change in a messinian evaporitic sequence vena del gesso italy iii stratigraphic changes in the molecular structure of kerogen in a single marl bed as revealed by flash pyrolysis abstract kerogens of nine samples from a single marl bed of the gessoso solfifera formation in the vena del gesso basin messinian italy were qualitatively and quantitatively studied by analytical pyrolysis relationships between the nature of the pyrolysis products and the source organisms were determined the high abundance of i algal derived components n alkanes and n alk 1 enes and ii sulphur containing and sulphur bound products signifying a high degree of early diagenetic sulphurization were observed presence of photic zone anoxia during the deposition of these sediments was discussed via the presence of 1 2 3 4 tetramethylbenzene in the pyrolysates unusual distributions were found for three series of pyrolysis products i e c13 and c14n alkylated thiophenes and thiolanes and c12 and c13n 1 3 alkadienes were by far the major products of these series in the pyrolysates of two samples corresponding to the middle of the cycle samples 3 and 5 which also have the highest 13ctoc values and the highest pyrolysis yields therefore the contribution of organisms biosynthesizing resistant algal biopolymer was considered as much more important during the deposition of the sediments associated with samples 3 and 5 we finally proposed partial structural elements from which the specific low molecular weight compounds of samples 3 and 5 can be derived upon pyrolysis