concentration and character of pahs and other hydrocarbons in coals of varying rank implications for environmental studies of soils and sediments containing particulate coal abstract particulate coal can occur in soils and sediments from both natural and anthropogenic sources its presence can influence the concentrations of regulated and more bioavailable pollutants through its geosorbent qualities and its own contribution of total extractable hydrocarbons teh including polycyclic aromatic hydrocarbons pahs and biomarkers extractable pahs in coal also can potentially affect pah based source and maturity ratios of soil or sediment extracts which can be used to assess the source s of pahs this study reports on the absolute concentrations of teh the 16 priority pollutant pahs 27 alkylated pahs and sulfur containing aromatics and selected biomarkers in 15 coals ranging in rank from lignite to anthracite unlike most previous studies in the fuel science or geochemical literature the coals herein were extracted using dichloromethane at room temperature an epa method 3500 type method common in environmental laboratories thereby allowing comparison of these results to environmental studies the concentrations of teh ranged from 8 2 to 2500 g g coal dry wt with a maximum yield among high volatile bituminous coals the teh fingerprints were variable and some of these resembled those of other forms of contamination the concentrations of priority pollutant pahs ranged from 35 to 11 000 ng g coal dry wt or 38 to 12 000 ng g carbon and varied with coal rank reaching a maximum within the high volatile bituminous rank the distributions of extractable pahs and numerous pah ratios conventionally used as source and or maturity parameters also varied with coal rank emphasizing that particulate coal in soils and sediments cannot be universally represented by a single set of diagnostic parameters hopanoid and sterane biomarker yields also varied with rank reaching a maximum in high volatile bituminous coals and were low relative to pahs because particulate coal often co occurs with other sources of hydrocarbons in soils and sediments the data presented herein may prove useful in allocating coal versus non coal sources on a mass balance basis

late jurassic bimodal magmatism in the northern sea floor remnant of the rocas verdes basin southern patagonian andes magmatic and detrital zircon ages from the rocas verdes basin a tectonically juxtaposed remnant of sea floor in the magallanes fold and thrust belt southern patagonia south america indicates that a rifting phase of the rocas verdes basin occurred between 152 and 142 ma and was accompanied by bimodal magmatism a dacite dyke cross cutting pillow basalt successions and a plagiogranite dyke in mixed mafic felsic terranes of the basal sarmiento ophiolite complex contain 150 ma zircon crystals indicating that mafic submarine volcanism had started prior to or during the late jurassic 10 15 ma earlier than previously thought the silicic pyroclastic rocks of the tobifera formation with two samples dated at 148 and 142 ma were heralded by synrift sedimentation along fault bounded grabens within palaeozoic metasediments no evidence for an active volcanic arc during the early formation of the rocas verdes basin was detected in detrital zircon grains of the lower sedimentary member of the tobifera formation a minimum of 25 ma of continuous sedimentation in the rocas verdes basin is suggested by detrital zircon grains in the upper member of the zapata formation the rocas verdes basin was rimmed on the western side by an incipient and subaerial magmatic arc only in its later evolution

petrological and geochemical composition of lignite from the d field kolubara basin serbia abstract the upper miocene lignite from the main coal seam in the d field kolubara basin is a typical humic coal with huminite liptinite and inertinite concentrations of up to 83 7 vol 17 2 vol and 15 5 vol respectively in the huminite group textinite and ulminite are the most abundant macerals with variable amounts of densinite and attrinite liptodetrinite and sporinite are the most common macerals of the liptinite group while inertodetrinite is the most abundant maceral of the inertinite group the mineral matter consists mostly of clay minerals the main sources of organic matter were gymnosperms conifers and microbial biomass followed by angiosperms based on composition of saturated and aromatic diterpenoids it has been established that coal forming plants belonged to the gymnosperm families taxodiaceae podocarpaceae cupressaceae araucariaceae phyllocladaceae and pinaceae peatification occurred in neutral to slightly acidic fresh water environment composition and distribution of biomarkers show that diagenetic changes of the organic matter were mainly governed by bacterial activity in a suboxic to oxic environment based on distribution of aromatic diterpenoids a novel diagenetic pathway for transformation of abietane type precursors under suboxic to oxic conditions is proposed variations in compositions of macerals and biomarkers are in concordance with pronounced seasonality during pontian which caused changes in the water level redox conditions during peatification and to some extent vegetation differences in the paleo plant communities

biomarkers of oligocene lacustrine source rocks beibuwan song hong basin junction offshore northern vietnam abstract highly oil prone source rocks containing sapropelic type i and mixed types i and iii kerogen are found in 233 m of the 500 m deep fully cored enreca 3 well drilled on bach long vi island located at the junction between the beibuwan and the song hong basins offshore northern vietnam the cored succession is made up entirely by oligocene deep lacustrine deposits the origin of the organic matter om in 62 samples is evaluated on the basis of gas chromatography mass spectrometry gc ms and gc ms ms om in 55 samples is sourced primarily from lacustrine organisms and contains abundant 4 methylsteranes tetracyclic polyprenoids tpp and lycopane and no markers for marine organic matter the proportion of triterpanes derived from angiosperms is low in most saturated fractions and only traces of gymnosperm diterpanes are detected in contrast all aromatic fractions have a high proportion of compounds having an origin from both gymnosperms and angiosperms very high concentrations of hopanoids in both fractions suggest significant bacterial alteration of the original om most samples have a high concentration of rare c31 diaromatic 8 14 secohopanes with a fluorene moiety low pristane phytane pr ph ratios indicate that anoxic suboxic bottom water conditions existed during om accumulation the presence of carotane gammacerane and traces of arylisoprenoids could indicate a stratified water column om in a few samples with lower than average hydrogen index hi is mainly of terrestrial origin with a higher proportion of c29 steranes diterpanes and oleanoids and lower concentrations of both saturated and aromatic hopanes higher pr ph a higher c34 isohopane ratio ihr34 and a lower homohopane index hhi indicate that this low hi om was originally deposited under more oxic conditions and subsequently transported to deeper water low sterane and hopane isomerization ratios show that no samples have reached the oil window some novel maturity parameters for immature lacustrine samples are proposed

organic geochemical investigations of brown coal lithotypes a contribution to facies analysis of seam banding in the helmstedt deposit abstract samples of light medium light and dark lithotypes from the eocene helmstedt brown coal deposit were examined by organic geochemical methods soxhlet extraction liquid and gas chromatography gc ms the study is part of a facies analysis of banded brown coals there are significant differences between the lithotypes concerning the extractable organic matter yields the composition of the extracts and the composition of the alkane fractions on average the light brown coals produce three times as much extractable organic matter as the dark ones asphaltenes and resins are the main components of the extracts of the light lithotypes hydrocarbons and n s o compounds of lower molecular weight are less abundant than in the dark lithotypes the alkane fraction of light lithotypes contains more n alkanes of high molecular weight and more saturated triterpenoids hopanes excluding homohopane but less unsaturated polycyclic compounds rearranged sterenes triterpenes and less homohopane the generally low concentrations of cyclic diterpanes norabietane norpimarane do not reveal any relationship to the three lithotypes based on these results there is no support for the conventional assumption that the light and dark brown coal lithotypes originated from different plant communities of the paleomoor the results rather suggest that the banding within the seam of the helmstedt brown coal deposit results from different biogeochemical degradation and transformation processes these processes are considered to be dependent on the environment of the paleomoor

comparison of the paleoclimatic significance of higher land plant biomarker concentrations and pollen data a case study of lake sediments from the holsteinian interglacial abstract a sediment core from the dethlingen paleolake holsteinian interglacial northern germany was subjected to integrated organic geochemical and palynological paleobotanical analyses in order to reconstruct past environmental conditions the fractionated lipid extracts were investigated using gas chromatography mass spectrometry gc ms and gc combustion isotopic ratio ms ring a aromatized pentacyclic triterpenoids most likely glutinane derivatives were the only higher plant derived pentacyclic triterpenoids found the saturated ring a degraded triterpenoid des a lupane was the most abundant aliphatic hydrocarbon throughout the core based on published pollen data which imply the strong presence of betula and alnus around the paleolake the des a lupane would be expected to originate mainly from lupane type precursors synthesized by betulaceae the carbon isotopic composition of des a lupane varied from 28 2 to 30 6 and no significant trend or isotopic shift was observed however the discrepancy between the variation in pollen data and biomarker concentration i e quasi absence of diterpenoids in the core argues for a scenario in which the two proxies represent different components of the vegetation in the catchment area of the paleolake

petrographical and organic geochemical study of the kovin lignite deposit serbia abstract the origin of the organic matter om and the characteristics of the depositional environment of lignites from the upper miocene kovin deposit hosting three coal seams of serbia were evaluated based on petrographic data bulk organic geochemical parameters biomarker analysis and stable isotope geochemistry 13c of individual biomarkers samples were collected from four boreholes gd 601 and gd 603 the a field and kb 79 and kb 91 the b field representing different parts of coal seams i ii and iii investigated lignites are typical humic coals the om of lignites is derived from woody vegetation and herbaceous peat forming plants with prevalence of the former in most samples peat forming vegetation is characterized by abundant decay resistant gymnosperm coniferous plants followed by a low amount of angiosperms lignite forming plants mostly belonged to the gymnosperm families cupressaceae taxodiaceae phyllocladaceae and pinaceae slight input of ferns fungi and aquatic macrophyta to lignite om is also evident distributions of hopanoids and isotopic compositions of these biomarkers reflect the activity of various microbial populations represented by methanotrophic chemoautotrophic and heterotrophic bacteria during diagenesis prominent c28 28 30 bisnorneohop 13 18 ene was observed for the first time in the lignite extracts according to the 13c value it was probably derived from chemoautotrophic bacteria c28 28 30 bisnorneohop 13 18 ene could be one of the possible precursors of a series of orphan aromatic hopanoids bearing an ethyl group at c 21 via progressive aromatization peatification proceeded in a fresh water environment under variable redox conditions from anoxic to slightly oxic all three coal seams are heterogeneous the lower parts of the coal seams represent a topogenous fresh water peat mire with open water areas which was subjected to inundations the upper parts of coal seams represent a wet forest swamp with relatively stable conditions despite the observed variations in all three coal seams the mean values of petrographic and organic geochemical parameters suggest general increasing of wetness and establishment of more stable conditions from seam iii to seam i maceral and biomarker data indicate that rapid flooding of the bogs stopped peat growth in all three coal seams relatively frequent variations in all three coal seams followed by repetition of lignite characteristics depict well the pronounced seasonality e g short term cycles of the climate during late miocene in investigated area

δ2 triterpenes early intermediates in the diagenesis of terrigenous triterpenoids a series of 2 triterpenoids oleana 2 12 diene oleana 2 13 18 diene oleana 2 18 diene ursa 2 12 diene and taraxera 2 14 diene has been identified in holocene buried mangrove sediments florida usa by comparison of the mass spectra of and by co injections with authentic standards in the oligocene brandon lignite vermont usa oleana 2 12 diene and oleana 2 13 18 diene were also identified along with two a ring contracted amyrin derivatives by comparison with the sedimentary occurrence of related analogues of oxyallobetulin and betulin and the demonstrated diagenetic formation of lup 2 ene from lupan 3 one these novel terrigenous biological markers are considered diagenetic products formed by dehydration of precursor molecules such as and amyrin and taraxerol the identification of these early intermediates brings us one step closer to the full understanding of the diagenetic fate of terrigenous triterpenoids

reinvestigation of the structure of a tetracyclic terpenoid from geological samples a novel marker for fungi involved in the degradation of buried wood abstract a tetracyclic compound tentatively assigned as a nor friedel 8 en 10 one was recently reported by bakar et al 2011 bakar n a tay k s omar n y m j abas m r b simoneit b r t 2011 applied geochemistry 26 1433 1445 from a malaysian lake sediment it was postulated to derive from friedelin via a sequence of diagenetic transformations involving the unprecedented removal of ring a and several hypothetical intermediates we considered that this structural assignment needed to be reassessed notably because we could detect the compound in wood samples devoid of friedelin related triterpenes firm identification was also needed since the compound is becoming used as a proxy in recent publications and its occurrence interpreted in terms of palaeoenvironmental reconstruction in the course of archaeometric studies of ancient buried wood the presence of the compound as a predominant constituent of the lipid extract of a buried alder wood sample gave us the opportunity to firmly establish its structure we report here its unambiguous identification using 1d and 2d nuclear magnetic resonance nmr spectroscopy after its isolation based on its structure geochemical distribution and stable carbon isotopic composition it appears that the compound likely does not derive from triterpenoids biosynthesized by higher plants but might derive from a precursor terpenoid synthesized by microorganisms bacteria fungi living within the buried wood and possibly involved in the degradation of plant organic matter wood notably

stratigraphic control on facies and diagenesis of dolomitized oolitic siliciclastic ramp sequences pinda group albian offshore angola pervasively dolomitized oolitic to siliciclastic ramp sequences are prolific oil reservoirs in the albian pinda group of northern angola during the late cretaceous this reservoir series was segmented by salt tectonic gravitational gliding into halokinetic turtle back and raft structures that provide hydrocarbon traps today the albian ramp sequences contain a large variety of reservoir facies reaching from littoral sandstones with interparticle porosity to various types of dolomitized marine shelf to shoreline carbonates with moldic vuggy and intercrystalline porosity reservoir prediction is substantially improved by an integrated approach combining high resolution sequence stratigraphy with carbonate geochemistry as high resolution stratigraphy documents most of the important sandstone reservoirs formed at the base of stratigraphic sequences during shoreface transgression pisolitic dolostones with moldic porosity are the best carbonate reservoirs they developed as transgressive shoreface sand sheets above the basal sandstone reservoirs regressive facies tracts contain oolitic and pisolitic dolomites with intercrystalline and moldic porosity that originated in progradational barrier and sand belt settings the combined stratigraphic and geochemical approach allowed us to determine the pinda group dolomites as early diagenetic in origin whereas fluid inclusion and oxygen isotope analysis alone suggested a late burial dolomite formation dolomite neomorphism at higher burial temperatures modified most of the original geochemical signatures of early near surface dolomitization cathodoluminescence data and trace element analysis suggest that dolomitization was associated with gradually decreasing pore water salinity accordingly barrier oolites were completely dolomitized and developed intercrystalline porosity during the earliest stages of diagenesis at a later phase of early diagenesis as waters became less saline and undersaturated with respect to calcium carbonate fabric selective dissolution of the remaining calcareous components occurred the decrease in pore water salinity and associated porosity generation are genetically linked with high frequency events of relative sea level lowering this possible relationship implies that high resolution sequence stratigraphy can be a valid reservoir prediction tool even in pervasively dolomitized series

paleoclimate influence on early diagenesis of plant triterpenes in the dajiuhu peatland central china abstract aromatic derivatives of vascular plant triterpenoids are common in recent and ancient sediments coal and petroleum understanding their early diagenetic alterations and their relation with environmental conditions can facilitate their applications in paleoenvironmental reconstructions here we present a high resolution record of aromatic triterpenes in a holocene peat core collected in the dajiuhu peatland central china these aromatic triterpenes are derivatives of plant triterpenoids with oleanane ursane and lupane carbon skeletons and exist in three different structural groups aromatic des a triterpenes aromatic pentacyclic triterpenes and c ring cleaved aromatic triterpenes such a high diversity of aromatic triterpenes in a young peat deposit is compelling evidence for rapid microbial mediation of these important degradation pathways during very early diagenesis of particular importance is the occurrence of c ring cleaved aromatic triterpene and aromatic des a triterpenes in the dajiuhu peat samples which until now have not been identified in recent sediments the downcore profile shows that the microbial aromatization process of oleanoids positively correlates with paleoclimate change during dry or warm intervals highly aromatized products such as tetraaromatic triterpenes become predominant over their triaromatic homologs in contrast triaromatic triterpenes become dominant during wet or cold intervals in addition this study provides further evidence to support that the climate pattern in the middle reaches of the yangtze river is different from that in north china during 13 9 4 ka these findings suggest that aromatic triterpenes can be valuable tools for holocene paleoenvironmental reconstructions

geochemical appraisal of palaeovegetation and climate oscillation in the late miocene of western bulgaria abstract palaeobotanical methods and geochemical techniques were used to assess plant contribution and palaeoenvironment for the staniantsi basin bulgaria the aim was to connect palaeovegetation change and climate oscillation based on pollen and statistical analysis with organic geochemical proxies for a late miocene lacustrine to paludial sedimentary succession three samples from lignite marl cycles were studied the biomarker assemblage and bulk chemical data indicated that gymnosperms were not important in the palaeomire the presence of des a triterpenoids 17 21 seco triterpenoids hopanes a high content of a d ring monoaromatic hopane and aromatized triterpenoids suggested that photochemical and microbial processes significantly contributed to the alteration of the organic matter om a prolonged period of high water table and severe mechanical destruction promoted microbial activity prior to burial and enhanced decay a geochemical appraisal of short term climate oscillation ca 21 7 kyr was attempted within the limitations of the small number of samples studied the cycles are expressed as lignite marl clay layers combined with cyclic changes in swamp vegetation related to cyclic changes in groundwater level and inundation of the basin in periods of low water level swamp phase lignite accumulation took place preliminary results for selected samples suggest that the oscillation may be reflected in the content of friedelin vs possible degradation products the ratio of a chromatographic peak tentatively assigned as a norfriedel 8 en 10 one to friedelin is proposed as a means of detecting short term environmental cycles where values 1 reflect periods of inundation however time series analysis using densely sampled lignite clay layer oscillations are needed to confirm the value of this biomarker ratio for environmental reconstruction

organic geochemistry of the lower miocene oberdorf lignite styrian basin austria its relation to petrography palynology and the palaeoenvironment abstract in the oberdorf trough at the northwestern margin of the styrian basin austria an up to 36 m thick lower miocene ottnangian lignite seam occurs within the fluvial koflach voitsberg formation previous results indicate that the lignite originated in a topogenous mire within a wet forest swamp palaeoenvironment differences in soluble organic matter som yield of borehole samples from the lignite seam are related to free lipids present in plant waxes or resins and the presence of thermally labile polymers indicated by the contents of liptinite macerals i e resinite suberinite and liptodetrinite the n alkane distribution patterns are dominated by high molecular weight lipids with marked odd over even predominance originating from plant waxes a contribution of algae to the even numbered short chain lipids observed in considerable amounts in the footwall sediments is proposed terpenoid biomarkers characteristic for conifers and angiosperms were detected consistent with palynomorphic spectra which are dominated by forest swamp pollen taxodiaceae cupressaceae and pollen from plants living in a mixed mesophytic forest excellent relationships between higher plant biomarker composition and palynologic data indicate that the organic geochemical results reflect the varying inputs of coniferales vs angiosperms the data further imply that cuparene may be used for taxonomical differentiation of coniferales families organic geochemical data provide evidence that the content of land plant derived biomarkers is controlled by the input of resin rich conifers concentrations of hopanoids dominated by hop 17 21 ene generally increase towards the top of the lignite a section characterised by high extents of aromatisation of triterpenoid biomarkers the results suggest that the aromatisation of angiosperm derived biomarkers may be governed by the activity of anaerobic rather than by aerobic bacteria however changes in the depositional environment and palynologic facies during peat formation probably influenced the origin and fate of angiosperm derived triterpenoids the results indicate how biomarker composition may contribute to the evaluation of environmental changes cross correlations of organic geochemical parameters with palynological data and petrography based facies indicators will provide further insights in the peat forming vegetation and biogeochemical activities in the mire

biomarker and micropetrographic investigations of coal from the krepoljin brown coal basin serbia abstract we investigated early diagenetic processes of the extractable organic matter from the miocene freshwater sequence which consists of coal fragments in clays sandstones and shales alternating with continuous brown coal layers we examined eight coals thirteen sediments and three non coaly underground layers the molecular assemblages of the identified aliphatic hydrocarbons in the krepoljin basin reflect the abundance of plant taxa as precursors or participants in the early diagenetic stage the data provide insight into the conditions prevailing in the lakes and bogs during early diagenesis the dominance of diterpanes indicates that the prevalent of the organic matter was of gymnosperous origin the hopanoid contents are considered to reflect microbial activity that the organic matter in the miocene krepoljin coal basin is immature was confirmed by the presence of biolipids such as hopanes c 27 17 h trisnorhopan saturated and aromatized abietanes pimaranes and phyllocladanes the most abundant compounds in all samples indicate a predominantly higher plant input related to the coniferous group but identification of the individual plant families was not possible amyrin and other triterpenoid derived triaromatic and triaromatic c ring cleaved hydrocarbons with triterpenoid structures are thought to be characteristic for angiosperms unsaturated compounds 2 triterpanes early intermediaries in the diagenetic transformation of angiosperms also indicate a low degree of sediment maturity

drake passage and cenozoic climate an open and shut case drake passage opening has often been viewed as a single discrete event possibly associated with abrupt changes in global circulation and climate at or near the eocene oligocene boundary a new plate tectonic model based on recent reinterpretations of the opening history of basins in the scotia sea suggests that an effective ocean gateway may have developed even earlier during the middle eocene this is consistent with a growing body of evidence from sediment core proxy data for eocene changes in southern ocean circulation and biological productivity the period between earliest opening after 50 ma and the latest eocene was characterized by the evolution of various current pathways across the subsiding continental shelves and intervening deep basins this shallow opening may have caused important changes in southern ocean circulation contributing to eocene cooling and the growth of antarctic ice sheets

internal structure of a contourite drift generated by the antarctic circumpolar current 1 we describe the internal structure and stratigraphy of a well imaged contourite drift from the southern ocean this drift which we have named the south falkland slope drift lies on the northern flank of the falkland trough due south of the falkland islands drifts which occur directly in the path of the antarctic circumpolar current acc downstream of the drake passage gateway are of considerable paleoceanographic significance since their detailed stratigraphic record will help to constrain the history of the acc we have reprocessed a grid of seismic reflection profiles generously provided by westerngeco ltd in order to enhance imaging of the south falkland slope drift and of drift deposits within the trough the resultant high quality images enable us to map the internal architecture of these drifts in unprecedented detail by combining seismic stratigraphic mapping with measured sedimentation rates from nearby boreholes we have inferred ages of the principal mappable horizons with minor adjustments to sedimentation rates through time we can show that these ages correspond to significant southern ocean events we propose that the south falkland slope drift initiated at 24 5 20 5 ma in accordance with some but not all published estimates of acc establishment a highly reflective horizon with an estimated age of 14 5 ma corresponds to growth of the east antarctic ice sheet which led to a period of significant global cooling a similarly bright reflective horizon with an estimated age of 9 ma is thought to be related to a reorganization of bottom current flow which just predated establishment of grounded ice sheets on the antarctic peninsular shelf finally a prominent early pliocene unconformity at 4 5 ma may be linked with the onset of major northern hemisphere glaciation or with antarctic ice sheet expansion we conclude that this well imaged drift is an important and largely continuous stratigraphic record of acc activity and suggest that it would be an excellent drilling target

sedimentary organic matter sources and depositional environment in the yegua formation brazos county texas abstract the complex depositional environment of the eocene yegua formation brazos county texas can be better understood by integrating organic matter om geochemistry with stratigraphy yegua sediments represent parasequences separated by exposure surfaces organic petrography and geochemistry biomarkers c n ratios and carbon isotopes indicate the presence of both terrestrial and marine om in transgressive sediments in contrast regressive sediments contain only terrestrial om these differences relate to contrasting om sources and depositional styles on the shelf om in the sediments is immature and the potential for generating hydrocarbons is poor the study suggests that organic geochemical data can help in distinguishing transgressive and regressive environments in sedimentary formations

alkane and pah biomarkers as tracers of terrigenous organic carbon in arctic ocean sediments abstract we present the first sedimentary biomarker study encompassing the entire arctic ocean a large data set of organic markers for terrigenous petroleum and combustion inputs alkanes hopanes and steranes parent and alkyl polycyclic aromatic hydrocarbons pahs is examined for patterns in space and time using principal components analysis pca and partial least squares pls biomarker patterns reveal the central arctic ocean basin sediments to be compositionally distinct from those of the mackenzie river beaufort sea and barents sea but similar to those of the laptev sea pah distributions reflected in pah ratios and pca projections demonstrate that arctic ocean sediment is dominated by natural inputs to the extent that anthropogenic combustion pahs are not significant we find only modest changes between the glacial and post glacial sediments for atmospherically transported hydrocarbon biomarkers while particle associated biomarkers were captured strongly at basin edges during the glacial period and much more evenly transported across basins during the post glacial period the orders of magnitude decreases in particle associated petrogenic alkanes and pahs in central basins during glacial times coupled with the uniformity of most petrogenic biomarker parameters for most basin and shelf locations reflect a massive reduction in ice transport that makes the margins the most likely source of petrogenic material for the pleistocene holocene central arctic basins the proximity of large coal deposits of various maturity levels along the lena river the overlap in pah and biomarker composition of the laptev sea and surficial sediments from the central arctic ocean and the location of the laptev sea at the origin of the main transpolar drift all point to eroded coals from the lena river laptev sea as the likely source of petrogenic hydrocarbons to the central arctic ocean the ubiquitous presence of allochthonous coal in arctic ocean surface sediments provides a major constraint on the use of petrogenic biomarkers to infer the presence of subsurface petroleum reserves

the central myanmar burma oil family composition and implications for source abstract geochemical characteristics of 31 miocene through eocene oils seeps an eocene coal and an eocene resin from the central myanmar burma basin system are examined the oils seeps vary widely in api gravity 8 52 sulfur concentration 26 3550 ppm 13 c 27 6 to 23 4 and molecular composition this variability is caused by varying amounts of biodegradation superimposed upon a single genetic oil family and the difference between aliphatic and aromatic hydrocarbon carbon isotope ratios i e 13 c arom 13 c aliph provides a useful gauge of the extent of biodegradation the projected geochemical characteristics of unaltered central myanmar oils are as follows a api gravity 35 37 b s 0 05 0 10 c 13 c aliph 27 8 to 27 6 d 24 ethylcholestanes are the dominant steranes and e 20s 24 ethyldiacholestane various bicadinanes and oleanane are present the ratio of 18 h 22 29 30 trisnorneohopane to 17 h 22 29 30 trisnorhopane t s t m is postulated as a maturity parameter and on this basis relative bicadinane concentration increases and the trans trans trans cis cis trans bicadinane ratio decreases with increasing thermal maturity in this oil set geologic arguments suggest a deep paleogene source for these oils two geochemical arguments that support this inference are a the occurrence of saturated and unsaturated c 15 and c 30 cadinane monomers and dimers in pyrolyzates of an eocene resin and the kerogen from an eocene coal and b identical compound specific carbon isotope ratios for selected isoprenoids and n alkanes in a typical central myanmar oil and the hydrous pyrolyzate expelled from an eocene coal we propose an eocene resinous shale coal source for these oils with the oldest eocene reservoirs filling first and the youngest miocene reservoirs filling last consistent with the observation that the least mature oils are present in the oldest reservoirs according to this model surface seepage and near surface oil could result from subsurface traps that are filled to spillpoint

depositional palaeoenvironment and economic potential of khadsaliya lignite deposits saurashtra basin western india based on petrographic palynofacies and geochemical characteristics abstract the lignite and associated shale of the khadsaliya clays formation eocene of saurashtra basin india have been studied organic petrographic palynofacies and organic geochemical analyses have been carried out to deduce the depositional palaeoenvironment including the assessment of the hydrocarbon potential of this sequence petrographically the lignites constitute huminite macerals in dominance av 60 the organic facies as derived from maceral composition and biomarker data suggests that the peat biomass was formed from woody forest vegetation consists of angiosperms and pteridophytes microbial activity was also prominent over the peat biomass the peat biomass was deposited in tropical subtropical humid climatic conditions under deltaic control and brackish water influence further there are signatures of intermittent floods in the mire and is evident from the shift from mesotrophic to rheotrophic conditions the organic matter has been categorized into two palynofacies and is derived from degraded terrestrial biomass the extrapolation of tyson s app diagram and pr n c17 vs ph n c18 plot suggest that deposition took place in dysoxic to sub oxic conditions the huminite reflectance values 0 30 0 38 av 0 34 rr suggest that lignites are less mature and have reached up to lignitic stage low rank b of coalification the geochemical proximate ultimate analyses reveal that the lignites are characterized by high moisture content av 18 and relatively low ash yield av 27 the volatile matter yields and carbon contents are moderately high whereas fixed carbon sulphur and oxygen contents are average and hydrogen and nitrogen contents are relatively low rock eval pyrolysis data indicate that the hydrogen index values of the samples vary between 23 and 477 mg hc g toc av 188 mg hc g toc the tmax values of the lignites range between 377 and 433 c av 418 c along with the presence of hopanes suggesting the immature nature of the deposits hi vs tmax s2 vs toc hi vs oi and h c vs o c plots of the studied samples indicate that the organic matters are a mix of type ii iii kerogens the types of kerogen along with high toc contents av 33 wt indicate the ability of lignite bearing sequence of khadsaliya to generate mix of oil gaseous hydrocarbons upon maturation

detrital zircon shrimp u pb age study of the cordillera darwin metamorphic complex of tierra del fuego sedimentary sources and implications for the evolution of the pacific margin of gondwana abstract the cordillera darwin metamorphic complex in the southernmost andes includes a basement of probable palaeozoic age a mid jurassic and younger volcano sedimentary cover and a suite of jurassic granites all of which were jointly metamorphosed during the cretaceous detrital zircon ages presented here show that some of the amphibolite facies metamorphic rocks previously mapped as basement have a jurassic protolith overall the detrital zircon age patterns for samples of the cordillera darwin basement differ from those of the madre de dios terrane of the western patagonian andes with which they had been correlated instead they are more comparable with those from the eastern andes metamorphic complex which apparently developed in a passive margin setting the paucity of cambrian detrital zircons indicates that the meta igneous basement of the magallanes foreland basin of central and northern tierra del fuego was not the main source of detritus for the protolith of the cordillera darwin metamorphic complex the possibility is envisaged that the magallanes fagnano transform fault boundary between the scotia and south america plates resulted from reactivation of an older pre jurassic suture zone between the basement terranes of north central tierra del fuego and cordillera darwin supplementary material geographical coordinates of analysed samples sensitive high resolution ion microprobe u th pb analytical data and representative cathodoluminescence images of zircon grains analysed are available at http www geolsoc org uk sup18397

hopane derived triterpenoids in soils the occurrence distribution and degradation pathways of hopanoid triterpenes have been studied in thirteen soil samples with varying degrees of biological activity hopanoids were shown to occur in all samples suggesting that they are not only ubiquitous in subaquatic sediments but also in soils hop 22 29 ene was generally predominant in the hydrocarbons whereas the 17 h 21 h bishomohopanoic acid c32 was the major component in the acids the concentrations of hopanes were usually rather low except in acidic peat the distribution in carbon number of hopanes and hopanoic acids showed great similarities with those of moderately oxic subaquatic sediments intact bacteriohopane tetrol widespread in microorganisms and the main precursor of geohopanoids was identified in substantial amounts in a peat exposed to groundwater oscillations

aliphatic and aromatic terpenoid biomarkers in cretaceous and paleogene angiosperm fossils from japan abstract the distributions of aliphatic and aromatic terpenoids in cretaceous and paleogene angiosperm fossils from japan were investigated aliphatic a ring degraded oleanane ursane and lupane were found in all samples in addition aliphatic gymnosperm derived diterpenoids were detected in significant quantities aromatic oleanane type triterpenoids were the major components with ursane and lupane type triterpenoids being minor compounds in all angiosperm fossils in a cretaceous gymnosperm fossil major components included aliphatic labdane isopimarane and abietane type diterpenoids aromatic abietane type diterpenoids and chrysene and picene type polyaromatic hydrocarbons pahs trace amounts of oleanane ursane and lupane type triterpenoids were also identified it is likely that the aromatic triterpenoids were introduced to the gymnosperm fossil from the angiosperm derived material in the sediments we defined an angiosperm gymnosperm index al agi as an alternative to the aliphatic triterpenoid diterpenoid ratio proposed in the literature the al agi index may underestimate the angiosperm contribution because the aliphatic angiosperm derived triterpenoids are more readily converted to aromatic counterparts than the diterpenoids during diagenesis an aromatic angiosperm gymnosperm index ar agi can be calculated using aromatic diterpenoids and triterpenoids we suggest that ar agi is best calculated using only the oleanane ursane and lupane type aromatic triterpenoids and that the chrysene and picene type pahs be excluded

geochemical characteristics of early carboniferous petroleum systems in western australia abstract a geochemical study was conducted to establish oil oil correlations and evaluate potential source rocks within the latest devonian earliest carboniferous succession of the onshore canning basin western australia aromatic hydrocarbons together with the routinely used saturated biomarker ratios and stable carbon isotopes demonstrate that the recently discovered ungani oilfield located on the southern margin of the fitzroy trough are similar but not identical to the early carboniferous larapintine 4 l4 oil family present to the north of the fitzroy trough on the lennard shelf the l4 oil family has been correlated to a lower carboniferous tournaisian source rock core sample from the laurel formation at blackstone 1 although its bulk geochemical properties signify that it could generate substantially more gas than liquid hydrocarbons the ungani oils can be distinguished from the l4 oils by their higher concentrations of paleorenieratane and isorenieratane coupled with more depleted 13c values for n alkanes pristane and phytane compared with other components hopane isomerisation ratios show distinct grouping of the two oil families that reflect both source and maturity variations the oil from wattle 1 st1 on the lennard shelf has an unusual composition exhibiting some molecular and isotopic features similar to both the l4 and ungani oils source rocks for the ungani and wattle 1 st1 oils are unknown since their geochemical signature does not match that of the tournaisian laurel formation or the middle upper givetian frasnian devonian gogo formation which sourced the devonian reservoired larapintine 3 oils at blina and janpam north 1 it is postulated that such potential oil prone source rocks could occur within the famennian tournaisian succession

aliphatic and aromatic hydrocarbons in candiota coal samples novel series of bicyclic compounds abstract aliphatic and aromatic fractions obtained from nine samples taken from two different seams of five boreholes in the candiota coalfield lower permian were analysed by gas chromatography mass spectrometry the occurrence of the tetracyclic diterpenoids 16 h phyllocladane and ent 16 h kaurane among the aliphatic hydrocarbons and the tricyclic diterpenoids simonellite and retene in the aromatic hydrocarbon concentrates suggest an important input from conifers to the sedimentary biomass this may explain the origin of a novel series of saturated and aromatic bicyclic compounds detected in the extracts which may be structurally related to the same precursor possibly a conifer resin derived tricyclic diterpenoid

palynology and paleoecology of lignites from the manning formation jackson group outcrop in the lake somerville spillway of east central texas abstract four palynomorph assemblages whose parent plants contributed to the formation of the lignite occur in the lignite seams and associated sediments from the manning formation jackson group outcrop in the lake somerville spillway of texas the cicatricosisporites laevigatosporites fern assemblage occurs in the middle and upper seam and probably derived from a freshwater herbaceous mire community the momipites coryloides arecipites columellus liliacidites assemblage occurs in all three seams and probably derived from a freshwater mire forest with an open canopy or shrub community the momipites coryloides nyssa rhoipites angustus assemblage occurs in the lower and middle seams and probably derived from a different freshwater mire forest the cupuliferoipollenites cupuliferoidaepollenites liblarensis siltaria cf s scabriextima assemblage occurs at the top of the lower and middle seams which are overlain by marine sediments the association between cupuliferoipollenites dominance and the presence of marine diatoms and brackish or marine trace fossils in the lignite suggests that this assemblage may have derived from a mangrove i e marine or brackish mire forest however other factors may influence its distribution ailanthipites berryi possibly derived from a tree or shrub related to the tree of heaven predominates in the claystone underlying the lower lignite seam and may have colonized the coastal plain prior to the initiation of peat accumulation we can differentiate lignite samples dominated by fern spores momipites pollen and cupuliferoipollenites pollen based on gas chromatography mass spectrometry gc ms fragmentograms of triterpanes m z 191 and steranes m z 217 the lignite layers dominated by each palynomorph assemblage appear to have distinct sources and different early diagenetic pre coalification histories

the paleogene vegetation and petroleum system in the tropics a biomarker approach abstract the present study investigates the biomarker signatures of sediments and crude oils to infer the paleovegetation from the two petroleum systems of assam basin eastern india they are classified as the paleocene middle eocene and the middle eocene oligocene petroleum systems the sediments are oil and gas prone with an early catagenetic stage of thermal evolution here we report tricyclic diterpanes such as rimuane pimarane rosane and isopimarane along with tetracyclic diterpanes ent beyerane phyllocladane kaurane from paleocene eocene coal bearing sediments and crude oils these diterpane biomarkers attest dominant contribution from conifers possibly from podocarpaceae and araucariaceae however diterpanes are not detected in oligocene sediments and oils crude oils from both paleocene eocene and oligocene reservoirs and organic rich sediments contain angiosperm biomarkers such oleanane and related triterpanes along with bicadinane a biomarker specific for the dipterocarpaceae family of angiosperms the equatorial position of india during early paleogene along with the presence of angiosperm signatures including dipterocarpaceae and gymnosperms reflect the emergence of tropical rainforest elements in eastern india absence of diterpenoids in oligocene samples and difference in angiosperm parameters from paleocene eocene samples suggests a change in source vegetation and organofacies

organic geochemistry of the lower suban coal seam south sumatra basin indonesia palaeoecological and thermal metamorphism implications abstract hydrocarbons extracted from the tertiary age coals from the lower suban seam south sumatra basin indonesia have been investigated using gas chromatography gc and combined gas chromatography mass spectrometry gc ms low rank vitrinite huminite reflectance 0 41 0 45 coals from the tambang air laya mine represent different maceral assemblages of an ideal succession of ombrogenous palaeo peat development in a vertical section high rank coals vitrinite reflectance 1 42 5 18 from the suban mine have been thermally metamorphosed by an andesitic intrusion variations in the distributions of n alkanes isoprenoids and saturated and aromatic biomarkers in the low rank coals reflect variations in local source input and palaeomire conditions terpenoid biomarkers such as cadinane and eudesmane type sesquiterpenoids and oleanane and ursane type triterpenoids indicate the predominance of angiosperm plants in the palaeomire particularly dipterocarpaceae the distribution of hopanoids is affected by the organic facies of the coal and their maturity and correlates with the palaeomire evolution as derived from petrological studies close to the igneous intrusion rapid thermal stress has destroyed most of the biomarkers but variations in n alkane distributions attributable to palaeomire conditions remain reversals in the trends for molecular parameters based on aliphatic hydrocarbons n alkane distribution and pristane phytane ratio and aromatic hydrocarbons methyl phenanthrenes with coal rank are observed

molecular composition of a leaf and root bearing oligocene oxbow lake clay in the weisselster basin germany abstract a plant fossil bearing clay profile from the upper oligocene thierbach strata weisselster basin germany has been sectioned into horizons and the plant macrofossils of each section surface have been identified by morphological and anatomical studies in the upper half of the profile leaves from populus germanica and carpinus grandis and branchlets from the conifer taxodium balticum vel t dubium dominate the horizons while the lower part contains only root remains of unknown higher plants in the soxhlet extracted samples from each section n alkanes n alkanols n carboxylic acids and several terpenoids amyrin 24 25 dinoreleana 1 3 5 10 12 tetraene olean 12 en 3 one simonellite and hop 17 21 ene were identified by combined gas chromatography mass spectrometry the comparison of the extracted chemical compounds and the macrofossil record of the profile shows that simonellite occurs preferentially in the taxodium bearing horizons n alkanes n alkanols n carboxylic acids and amyrin were found in all sections but are enriched in the root containing part of the profile the distribution of hop 17 21 ene is independent of the input of higher plant remains

conifer and angiosperm biomarkers in clay sediments and fossil plants from the miocene clarkia formation idaho usa the aliphatic lipids and terpenoids of conifer and angiosperm macrofossils and the clay sediment from a new site p 37 of the miocene clarkia formation idaho usa were analyzed to evaluate the preservation of characteristic conifer and angiosperm biomarkers in the sediment series of aliphatic lipids terpenoids and steroids similar to the biomarkers found in type locality clarkia p 33 were the predominant compounds in the sediment and in the fossils long chain aliphatic lipids were major compounds in the fossil plants and the sediment but a differentiation of angiosperm and conifer sources is not possible due to their common distribution among all vascular plants in addition to previously reported terpenoids diterpenoids of a conifer origin and several angiosperm derived polar triterpenoids of the oleanane lupane ursane and friedelane classes are reported here for the first time from the clarkia sediments the conifer shoots taxodium glyptostrobus calocedrus contained characteristic conifer biomarkers such as abietane type diterpenoids while characteristic angiosperm triterpenoids were predominant in the angiosperm leaves betula quercus lithocarpus the biomarker compositions of the taxodium and glyptostrobus shoots match the terpenoid patterns previously reported from fossil seed cones of the same genera although conifer macrofossils contribute about 45 to the flora of site p 37 characteristic conifer biomarkers occurred in the sediment in only low amounts while the angiosperm derived triterpenoids were present in comparatively higher abundances the results indicate that the conifers are under represented compared to the angiosperms according to the terpenoid composition of the sediment extract this may be due to the presence of small angiosperm derived particles leaf detritus wax in the sediment and or migration of leaf waxes from the angiosperm leaves into the sediment in contrast the diterpenoids are trapped in the resinous woody tissue of the conifers and are thus disseminated less into the sediment

aromatic hydrocarbons in the paraiba valley oil shale abstract aromatic hydrocarbon fractions extracted from different depths of a core 13 8 47 3 m deep of the paraiba valley oil shale were analysed by computerized high resolution gas chromatography mass spectrometry triterpenes derived from precursors oxygenated at position 3 such as tetracyclic ring a degraded and pentacyclic aromatic ursane oleanane and lupane derivatives were amongst the most common components indicating an important input from higher plants to the sediment this interpretation is supported by the occurrence of sesquiterpenoids cadalene calamenene in the same sediment samples on the other hand hopanoids notably the tetraaromatic derivative were also detected attesting to a significant bacterial contribution to the sedimentary biomass in contrast with the abundance of aromatic structures related to oleanane ursane and hopane no skeletons traceable to steroidal precursors could be confirmed suggesting a small algal input this study also revealed the presence of two new aromatic biomarkers one of them is a c24 monoaromatic tetracycle apparently derived via ring a degradation from a triterpenoid with the fernene skeleton the other compound is a ring a monoaromatic pentacycle with what appears to be a hopanoid structure

variability in coal facies as reflected by organic petrological and geochemical data in cenozoic coal beds offshore shimokita japan iodp exp 337 abstract this study reports on cenozoic coal seams recovered at integrated ocean drilling program iodp site c0020 during expedition 337 iodp site c0020 is located in a forearc basin formed by the subduction of the pacific plate off shimokita peninsula japan hole c0020a penetrated 14 coal layers between 1825 and 2466 mbsf eleven of them were investigated within the frame of this paper investigated seams show a slight maturity increase with depth from lignite to sub bituminous coal in order to detect temporal changes in maceral and molecular composition and to relate them to changes in vegetation and depositional environment macro and micropetrographic data bulk geochemical parameters biomarker analysis stable isotope geochemistry and vitrinite reflectance measurements were performed results were also compared with palynological data obtained from 9 coal samples elevated sulfur contents and high ash yields occur in the upper seams cores 14r to 18r whereas low sulfur contents and varying ash yields were determined for the lower coal seams 24r to 30r the maceral composition and biomarker ratios of the uppermost seams argue for coal formation in a paralic environment and brackish alkaline water conditions in contrast lignite samples from the lower part of unit iii point to a limnic fluviatile deposition conifers contributed significantly to peat formation in the uppermost seams from cores 15r to 22r and in the lowermost lignite seam in all other samples angiosperms are considered as the major peat forming plants the pollen and spore floras indicate rich angiosperm vegetation however significant contributions from pinaceae and taxodiaceae are evident for all coals sporophytes have no dominant influence on the coal flora microbial activity in the peat is suggested for instance by higher concentrations of hop 17 21 ene with increasing contents of hopanes or by low 13 c values of hop 17 21 ene the revealed changes in the environment during coal deposition highlight the importance of combined organic petrography organic geochemistry and palynology to reconstruct palaeoenvironmental conditions

biomarker evidence for intermittent photic zone euxinia in the aptian albian organic sedimentary record from the ionian zone epirus greece new biomarker evidence is presented that constrains the conditions of deposition and preservation of sediments rich in extractable organic matter from the aptian albian sedimentary record of the ionian zone in nw greece analyses were specifically carried out on total lipid extracts from 12 organic rich samples from the vigla shale member two of which represent the regional record for the early albian paquier event of oae1b in the aliphatic fractions compound groups such as n alkanes isoprenoid alkanes steroids hopanoids and terpenoids were recognized pointing to a mixed origin from algae and prokaryotes with an additional measurable contribution from terrigenous plant matter these compounds suggest deposition of the primary organic sediments under conditions of decreased bottom water oxygen concentrations mass spectral evidence from the aromatic fractions of most samples reveal the variable presence of diagenetic and catagenetic derivatives of carotenoid pigments including some with bound sulfur that are characteristic of photoautotrophic sulfur bacteria the presence of specific biomarkers originating from photosynthetic anaerobic microorganisms similar to those in ancient and contemporary euxinic basins such as the black sea suggest that photic zone euxinic conditions were intermittently operative in the aptian albian stages of the ionian basin but were not exclusively characteristic of the black shale representing the paquier event itself

the geochemistry of aliphatic and polar organic tracers in sediments from lake bera malaysia abstract the molecular distributions of homologous aliphatic lipid compounds n alkanes n alkanoic acids n alkanols n alkanals and n alkan 2 ones were investigated in sediments of lake bera malaysia as well as in plant waxes from the vicinity using gas chromatography mass spectrometry in addition triterpenoids of the oleanane ursane lupane and friedelane series and their diagenetic products were also identified using the aquatic proxy p aq it was found that the n alkanes present in surface sediments s1 s5 and s6 correspond to an input from emergent macrophytes whereas in sediments collected from open water s2 s3 and s4 they correspond to input from submerged floating macrophytes the presence of n alkan 2 ols a commonly found homologous series in the sediments as well as in the plant wax is novel here in addition the presence of 24 methylcycloart 22 enol and 24 ethylcycloart 22 enol in sediments as well as the plant wax of pandanus helicopus a dominant reed around the lake also supports the input of plant biomarkers to the sediments the occurrence of 5 membered ring triterpenoid derivatives as major diagenetic products of the triterpenoids identified e g friedelan 2 3 dione shows that the degradation of the organic matter in the sediments occurs mainly under oxic conditions also the presence of ring a degraded triterpenoids dihydroputranjivic acid 3 nor 2 4 seco friedelane 4 and 4 3 norfriedelanes a norfriedel 10 one and a norfriedel 8 en 10 one and the aromatized triterpenoid hydrocarbons mono and triaromatic derivatives as minor diagenetic products indicates photochemical and microorganism mediated alteration reactions of natural products in the sediments additional novel polyfunctional friedelane derivatives namely friedelane 2 3 dione friedelane 1 3 diol 2 one and friedel 1 10 ene 1 3 diol 2 one were identified for the first time in this study these novel polyfunctional triterpenoids were inferred to derive from the oxidation of the triterpenoids from higher plants in this oxic tropical environment for future reference purposes the mass spectra of the identified polar triterpenoids are also presented here this study provides important data on the biogeochemistry of organic matter in a tropical lake of se asia

biogeochemistry of the miocene lacustrine deposit at clarkia northern idaho u s a abstract the lipid preservation observed in the sediments from clarkia reflects an extremely immature thermal history many biomarkers have still retained functionality even after 17 20 million years the soluble components are predominantly higher plant and algal derived lipids and the original sources for these compounds are still preserved in the sediment thus biogeochemical data are in agreement with the associated palaeontological evidence chemical changes noted in the lipids preserved in these sediments are similar to those observed in modern fresh water mesotropic or eutrophic lacustrine sediments therefore it can be inferred that the processes that operate in modern lacustrine sediments are similar to those that took place within the sediments at clarkia 17 20 million years ago

transition from back arc to foreland basin development in the southernmost andes stratigraphic record from the ultima esperanza district chile during the mesozoic evolution of the southernmost andes back arc basin formation in an extensional setting was followed by foreland basin development in a compressional setting a stratigraphic record of this tectonic transition is described from jurassic and cretaceous rock units exposed in the patagonian fold thrust belt at 51 s latitude initiation of an extensional deep marine trough in late jurassic time is documented by interstratified rhyolites and marine mudstones in the tobifera formation development of the early cretaceous rocas verdes back arc basin is recorded by zapata formation submarine slope deposits which draped the west facing passively subsiding cratonic margin of the basin the onset of andean compressional orogenesis and creation of the magallanes foreland basin is marked by the influx of coarse grained sandstone turbidites of the albian cenomanian punta barrosa formation during late cretaceous time the foreland basin configuration consisted of a narrow foredeep trough bounded by a gently sloping foreland ramp on the craton to the east this geometry reflects greater flexural subsidence of the stretched and thermally weakened passive back arc basin margin beneath the load of the obducted rocas verdes basin floor changes in depositional regime and sediment dispersal patterns in the latest cretaceous together with an eastward shift in the magallanes basin depocenter record cratonward migration of deformation in the patagonian fold thrust belt loading of the thicker cratonic lithosphere caused subsidence of the foreland ramp to form a wide flexural basin

triterpenes in a nigerian oil abstract a series of monounsaturated triterpenes have been identified in an oil from utue field of the niger delta the triterpenes are the angiosperm derived olean 13 18 ene olean 12 ene olean 18 ene baur 7 ene and urs 12 ene the presence of these compounds in oils is attributed to the extraction of thermally immature agbada shales by the migrating fluid and in the reservoir the terpane biomarker signature of the oil does not appear to have been altered by this phenomenon

late oligocene initiation of the antarctic circumpolar current evidence from the south pacific the antarctic circumpolar current acc is a key feature of the southern ocean its development may have helped cool antarctica and initiate southern hemisphere glaciation the deep circulation of the acc must have been established after both the tasman gateway between antarctica and australia and the drake passage between south america and antarctica opened however estimates for acc initiation range over 20 m y from the middle eocene to early miocene a new piston core of upper oligocene to holocene sediments from the south pacific has allowed us to delimit the formation of the acc to the late oligocene ca 25 23 ma upper oligocene current worked sediments and a hiatus to the upper miocene result from the beginning of the modern acc flow i e when strong currents and mixing throughout the water column were established previously published nd isotope data date the first intrusion of pacific water into the atlantic much earlier the discrepancy with our results can be reconciled by the different methods measuring different flow regimes tracer methods such as nd are sensitive to relatively small and shallow incursions of water whereas pelagic erosional regimes require vigorous deep flow

glacial to postglacial transformation of organic input pathways in arctic ocean basins 1 the arctic ocean is undergoing rapid loss in ice cover with yet unknown consequences for the cycling of organic material here we examine persistent terrigenous land based alkane and polycyclic aromatic hydrocarbons with vascular plant combustion and petrogenic sources in seven cores collected from all major basins of the arctic ocean for insight as to how organic cycling at the last glacial maximum compares to the present day we find only modest changes between the glacial and postglacial sediments for atmospherically transported hydrocarbon biomarkers demonstrating that glacial sea ice was not a barrier to atmospheric inputs in stark contrast particle associated biomarkers were captured strongly at basin edges during the glacial period and much more evenly transported across basins during the postglacial period evidently the capture of organic matter shifted from the slopes to the shelves as the latter flooded during the holocene and the transpolar drift and beaufort gyre evolved from minor carriers of plant detritus from the glacial ocean margins to major modern transporters of shelf sediment to the basins this suggests that changes in organic transport currently accompanying the loss of sea ice are likely to be very different from those that occurred at the end of the last glacial period

successful exploration of the outer pinda trend of offshore cabinda angola areas b and c offshore cabinda cover 675 050 ac 2 732 km and are held by cabinda gulf oil company operator sonangol agip angola and elf petroleum angola recent exploration has been very successful over 5 x 10 sup 9 bbl of oil in place and over 10 x 10 sup 12 ft sup 3 of gas have been discovered in the lower cretaceous pinda formation the first discovery was the n dola field in 1972 but the discovery of the sanha field in 1987 led to the recognition of the potential of the trend the hydrocarbons are found primarily in eight fields situated in water depths ranging from 255 to 425 ft 68 to 130 m and located 50 to 65 km from the onshore malongo terminal the pinda formation is approximately 4000 ft 1220 m thick and is a cyclic carbonate siliciclastic sequence deposited in a sabkha to shallow marine environment the best reservoirs are in fine to medium grained subarkosic sandstones deposited in a nearshore environment diagenesis is important in determining reservoir quality the structure of a typical field is a fault bonded antiformal raft containing one or more rotated fault blocks separated from neighboring blocks through gravity sliding on the underlying salt decollement surface hydrocarbonmore columns range from 1000 to about 2500 ft 305 to 760 m first production from the kokongo field which will become the gathering station for all area b and c production is scheduled for 1994 less

continental underthrusting and obduction during the cretaceous closure of the rocas verdes rift basin cordillera darwin patagonian andes 1 the patagonian andes record a period of cretaceous neogene orogenesis that began with the compressional inversion of a late jurassic rift called the rocas verdes basin detrital zircon ages from sediment that filled the southern part of the basin provide a maximum depositional age of 148 ma suggesting that the basin opened approximately simultaneously along its length during the late jurassic structural data and u pb isotopic ages on zircon from granite plutons near the beagle channel 55 s show that basin inversion involved two stages of shortening separated by tens of millions of years an initial stage created a small 60 km wide thrust wedge that placed the basaltic floor of the rocas verdes basin on top of adjacent continental crust prior to 86 ma structures and metamorphic mineral assemblages preserved in an exhumed middle to lower crustal shear zone in cordillera darwin suggest that this obduction was accompanied by south directed subduction of the basaltic crust and underthrusting of continental crust to depths of 35 km beneath a coeval volcanic arc a subsequent stage of out of sequence thrusting culminating in the paleogene shortened basement and upper jurassic igneous rock in the internal part of the belt by at least 50 km forming a bivergent thrust wedge this latter period coincided with the exhumation of rocks in cordillera darwin and expansion of the fold thrust belt into the magallanes foreland basin this orogen provides an important example of how orogenesis initiated and led to continental underthrusting and obduction of basaltic crust during closure of a quasi oceanic rift basin

late cretaceous paleogene palaeoclimate reconstruction of the gippsland basin se australia abstract the cretaceous paleogene palaeovegetation and palaeoclimate in the gippsland basin was reconstructed using vascular plant derived biomarkers and are consistent with other proxy evidence for palaeoclimate e g spore pollen assemblages and plankton foraminifera oxygen isotopes variation in the higher plant derived aliphatic and aromatic sesquiterpenoids diterpenoids and triterpenoids resulted from vegetation succession and is different in the t lilliei f longus l balmei m diversus p asperopolus and n asperus palynological biozones analyses of the oleanane index the higher plant parameter the higher plant index the higher plant fingerprint and various aliphatic and aromatic angiosperm gymnosperm indices indicate the late cretaceous paleogene ca 80 40 ma palaeoclimate in the gippsland basin was initially warm campanian t lilliei biozone and then changed in this way cool maastrichtian upper f longus biozone warm paleocene l balmei biozone hot early eocene m diversus and p asperopolus biozones warm and then cool middle eocene n asperus biozone this changing climate trend is mostly consistent with global climate changes in comparison to the analogous taranaki basin western new zealand the gippsland basin is inferred to have had a less gymnosperm dominated rainforest and a warmer climate in the late cretaceous during the paleogene the palaeoclimate was similar in the two basins as deduced from the angiosperm gymnosperm indices of the sedimentary rocks

holocene land cover dynamics in the curuai floodplain inferred from lacustrine biomarkers this study on curuai floodplain central amazonia sediments last 5600 cal yr bp focused in rock eval re hydrogen hi and oxygen oi indices tmax s2 curve and tps2 organic petrography and molecular biomarkers n alkanes hopanes pentacyclic triterpene methyl ethers ptmes and derivatives of pentacyclic triterpenes such as des a lupane and aromatic derivatives analyses between 5600 and 5100 cal yr bp the environment was waterlogged and dominated by emersed plants paq 0 27 0 38 the influence of the amazon river was low terrestrial vs aquatic ratio t a 0 8 cpi values 3 4 and high contents of ptme 0 22 1 54 g g sed and aromatics 21 53 g g sed indicated a strong contribution of terrestrial material and anoxic om deposition conditions between 5100 and 5000 cal yr bp more humid conditions due to heavier rainfalls were observed early in this period terrestrial biomarker contents 253 g g sed of aromatics paq 0 17 increased due to input of watershed erosion material this provoked a rapid burial and good preservation of terrestrial om cpi 3 4 5 from 5000 cal yr bp a strong sedimentation of carbonate minerals oi 1600 mg co2 g 1 masked the om signal and affecting re parameters paq 0 18 t a ratio 0 4 and the decrease of c31 c31 hopanes 1 18 indicate increasing aquatic conditions up to 2700 cal yr bp cpi ratio 1 2 and degraded phytoclasts suggest intense degradation during transport to the sedimentation location the ptmes results showed that from 3000 yr cal bp the poaceae genuses were different from those found at the bottom middle holocene suggesting a change of vegetation the last 600 cal yr bp were marked by the seasonal influence of the amazon river during periods of low water level the organic petrography and cpi values 1 0 evidenced om degradation and the return of rather drier conditions

structural and stratigraphic evolution of the western malvinas basin argentina the malvinas basin is one of the few basins on the argentine continental shelf that contains a proven petroleum system however uneconomical oil discoveries keep the basin at a frontier exploration status the malvinas basin evolved through three main tectonic phases rift sag and foredeep the sedimentary fill of the basin is closely related to its tectonic history middle jurassic rifting resulted in north northwest oriented grabens that filled with volcanic and pyroclastic continental rocks diminished faulting and generalized subsidence during the late jurassic neocomian early sag phase were accompanied by deposition of a basal transgressive marine wedge the aptian maastrichtian interval was characterized by tectonic quiescence and deposition of offshore mud prone sediments southerly localized early paleogene transtensional tectonism accompanied the early development of a foredeep trough outer shelf glauconite rich sandstones basinal claystones and localized carbonate buildups partially filled the basin by the middle eocene oligocene a strong deepening event marked the initiation of the foredeep sensu stricto phase this phase resulted in the full development of the malvinas foredeep and the formation of compressional structures in the foreland the foredeep basin was replenished by a westerly derived offlapping siliciclastic wedge of oligocene miocene age noncommercial hydrocarbon discoveries in 5 of the 17 wells drilled in the basin suggest the presence of an undercharged lower inoceramus springhill petroleum system

saturated and aromatic diterpenoids and triterpenoids in eocene coals and mudstones from china several series of saturated diaromatic triaromatic c ring cleaved and triaromatic diterpenoids and triterpenoids have been detected in 4 immature coal and mudstone samples a number of these compounds appear to represent intermediates in a series of postulated pathways for progressive aromatization of biogenic diterpenoids and triterpenoids diagenetic pathways for the formation of tricyclic aromatic hydrocarbons from abietane and pimarane type diterpenoid precursors and for the formation of diaromatic triaromatic c cleaved and triaromatic hydrocarbons from amyrin and other triterpenoid precursors are proposed saturated and aromatized abietanes pimaranes and phyllocladanes which are the most abundant compounds in all 4 samples indicate a predominant higher plant input which can be related to the coniferales group but not to individual plant families amyrin and other triterpenoid derived triaromatic and triaromatic c ring cleaved hydrocarbons with triterpenoid structures are thought to be characteristic for angiosperms the relative concentrations of the triaromatic and triaromatic c ring cleaved hydrocarbons are higher in samples 9602 mudstone and 9603 coal than samples 9601 coal and 9604 mudstone indicating samples 9602 mudstone and 9603 coal contain relatively more angiosperm derived organic matter than samples 9601 coal and 9604 mudstone the distribution patterns and the relative concentrations of saturated and aromatic diterpenoids and triterpenoids thus are valuable markers for the determination of the relative contents of biological sources of organic material in geological samples

bicadinanes and other terrestrial terpenoids in immature oligocene sedimentary rocks and a related oil from the surma basin n e bangladesh abstract the aliphatic fractions and one aromatic fraction of outcropping oligocene rocks from the ne surma basin of bangladesh were studied by gc ms and compared with their subsurface equivalents and one oil sylhet from boreholes further south in the basin terrestrial biomarkers frequently encountered in these rocks whose biomass is dominantly woody include the triterpanes oleanane and bicadinane several tetracyclic terpanes and the sesquiterpenoids cadinane and cadalene the bicadinanes and their aromatized counterparts are found as major triterpenoid components only in the upper jenam formation where the richest horizons are interpreted to contain locally derived concentrations of dammar type resin excluded from dipterocarpaceae or similar tropical angiosperm trees vitrinite reflectance and geochemical maturity parameters indicate pre oil window maturity for the upper jenam outcrop allowing a temperature of less than about 90 c to be estimated for the formation of bicadinanes from resinous polymer cis cis trans bicadinane which is abundant in sylhet oil was not positively identified in any of the rock extracts although the distribution of bicadinanes is otherwise very similar

contrasted distributions of triterpene derivatives in the sediments of lake caco reflect paleoenvironmental changes during the last 20 000 yrs in ne brazil lipid fractions extracted from sediment layers deposited in a small brazilian lake during the last 20 000 yrs were investigated by gas chromatography mass spectrometry considerable differences in the distribution and the amount of triterpene derivatives in the aliphatic as well as in the aromatic fractions were observed all along the series although no precise identification of these compounds was undertaken our interpretation of mass spectral data allowed us to discriminate between des a triterpenes mono and triaromatic derivatives of pentacyclic triterpenes and a series of compounds tentatively identified as diaromatic derivatives of tetracyclic triterpenes the largest compound diversity was found in the lowest levels of the series dated back to the end of the last glacial maximum when good preservation of terrestrial plant debris was ensured by rapid burial in a semi arid climate then except for a period corresponding to the younger dryas only des a lupane was detected in significant amounts the high predominance of des a lupane is interpreted to result from the development of a belt of eleocharis sp spike rush that filtered most of organic inputs from the catchment and was the site of des a lupane production and exportation towards the lake centre during the younger dryas a strong influx of des a lupane is attributed to the destruction of the spike rush belt consecutive to the lowering of the lake level under drier conditions the temporary destruction of this barrier allowed other triterpene derivatives to reach the lake the distinct dynamics of des a and aromatic triterpene derivatives under variable medium conditions led us to hypothesis that these two families of compounds derive from distinct pools that contributed differently to the sediment depending on environmental and climatic conditions des a lupane was most probably produced in sub aquatic conditions within the belt of spike rush conversely aromatic derivatives of triterpenes could have resulted from the degradation of their biological precursors within reducing micro environments in the catchment

comparative study of serbian miocene coals insights from biomarker composition abstract the origin of the organic matter om and the characteristics of the paleoenvironment of serbian brown coals covering a time span from the lower to the upper miocene were evaluated and compared based on comprehensive petrological and biomarker analyses investigated coals are typical humic coals peat forming vegetation is characterized by abundant decay resistant gymnosperm coniferous plants followed by variable amount of angiosperms coal forming plants belonged to the gymnosperm families taxodiaceae podocarpaceae cupressaceae araucariaceae phyllocladaceae and pinaceae peatification proceeded in fresh water environment under variable eh settings from anoxic to slightly oxic condition upper miocene lignites were formed in neutral to slightly acidic environment whereas lower and middle miocene coals were deposited under neutral to slightly alkaline and more reductive conditions which is the result of calcium rich surface waters derived from the surrounding jurassic to cretaceous calcareous country rock and higher water column level diagenetic changes of the om were governed by bacterial activity rather than thermal alteration biomarker pattern does not significantly differ in serbian coals of different ages the main differences between upper middle and lower miocene coals are expressed by higher gelification index gi proxy ratio p aq n c 23 n c 27 n c 31 and pimarane 16 h phyllocladane ratio as well as lower relative abundance of c 31 r hopane of the latter one om of lower miocene coals is more mature corresponding to immature early mature stage huminite vitrinite reflectance 0 45 whereas om of upper miocene lignites is in immature diagenetic phase huminite reflectance 0 3 consequently higher gelification of lower miocene coals is probably an effect of higher rank however high humidity wet climate and low acidity within the mire could not be excluded a good correlation between biomarker parameters and paleoclimate data is observed indicating that biomarker patterns represent a valuable tool that reflect even slight paleoclimate changes in serbia during miocene

petrological and organic geochemical properties of lignite from the kolubara and kostolac basins serbia implication on grindability index abstract the influence of different coal lithotypes on grindability has been investigated using lignite from two of the most important upper miocene lignite basins in serbia kolubara and kostolac yellow xylite rich types demonstrated the most negative impact on hardgrove grindability index hgi all different types of xylite rich coal as well as total xylite rich coal from the kolubara basin have a negative influence on the grindability properties while only the yellow type of xylite rich coal from the kostolac showed a negative impact on hgi matrix coal does not show a clear effect on hgi a negative correlation between textinite content and hgi is observed in both basins whereas contents of other macerals do not show influence on grindability properties content of total organic carbon demonstrated the negative impact on hgi correlation analysis indicates that the negative impact of the yellow type of xylite rich coal and the sum of total xylite rich coal on the grindability properties partly can be related to content of total organic carbon and high amount of soluble organic matter matrix lithotype does not show any significant correlation with bulk geochemical parameters in both basins the peat forming vegetation of all samples from both basins were dominated by decay resistant gymnosperm coniferous plants belonging to one or several of the families taxodiaceae podocarpaceae cupressaceae araucariaceae phyllocladaceae and pinaceae lignite from the kolubara basin is characterized by a higher contribution of angiosperm vegetation than coal from the kostolac basin peatification of the kolubara coal occurred under more oxic conditions than the kostolac one analysis of biomarkers indicated that the negative impact of all types of xylite rich coal from the kolubara on hgi can be related to the higher proportion of angiosperms abundance of mid chain n alkanes and sesquiterpenoids aromatization of non hopanoid triterpenoids and hopanoids and intense degradation of wood tissues in a more oxic environment the positive impact of matrix coal on hgi in the kolubara samples can be attributed to elevated content of non aromatic hopanoids and low amounts of aromatic non hopanoid triterpenoids and sesquiterpenoids which seems to hinder the grindability properties

molecular indicators of diagenesis in lignite diastereomeric configuration of triterpenoid derived aromatic hydrocarbons abstract the ratio of tetramethyloctahydropicene diastereomers i and ii is shown to vary as a function of a depth b lithotype and c seam in a 100 m core of continuous coal taken from the latrobe valley victoria this is the first illustration that triterpenoid derived aromatic hydrocarbon diastereomers can be used as molecular indicators of diagenesis

oleananes in oils and sediments evidence of marine influence during early diagenesis abstract the oleananes as markers for the angiosperms provide valuable source and age information when present in an oil nevertheless they are not quantitatively related to the land plant input and indeed their presence reflects only a small leak in diagenetic processes leading primarily to aromatic oleanoids because they are minor products the abundance of oleananes in terrigenous oils and sediments may be highly sensitive to changes in early diagenetic conditions here we present evidence that contact of plant matter with seawater during early diagenesis enhances the expression of oleananes in a mature sediment or oil oleananes are absent or present at very low concentrations in samples from the base of an eocene coal seam affected by postdepositional seawater intrusion however their abundance increases toward the top of the seam in correlation with organic sulphur dibenzothiophene phenanthrene and the homohopane index similarly in deltaic sediments from the south sumatra basin oleanane hopane is strongly correlated with indicators of marine influence such as c 27 c 29 steranes and the homohopane index in each case increasing oleanane abundance is accompanied by a reduction in the extent of aromatisation and for the south sumatra basin the proportion of a ring contracted oleananes an angiosperm derived miocene coal from the philippines deposited under freshwater conditions shows abundant aromatic oleanoids but no oleananes these results show that oleananes need to be used with caution as age and source markers in fluvio deltaic and lacustrine petroleum systems on the other hand their sensitivity to early diagenetic conditions may make them useful in locating effective source rocks in such systems

early eocene equatorial vegetation and depositional environment biomarker and palynological evidences from a lignite bearing sequence of cambay basin western india abstract an investigation of palaeofloral distribution with depositional environment and palaeoclimatic condition of western indian subcontinent during early eocene period has been carried out from a lignite bearing succession of cambay basin western india the study of biomarkers palynological remains and petrography is taken as proxies for providing supportive evidence for our inference the petrographic results reveal that the sediments are thermally immature and coalification was extended up to the lignitic stage low rank b the palynological results show the dominance of angiosperms mainly members belonging to the arecaceae family throughout the studied section triterpenoids with oleanane ursane and lupane structure in extractable organic matter are derived from angiosperm wax pollen grains spinizonocolpites proxapertites dipterocarpuspollenites albertipollenites retipollenites arengapollenites lakiapollis and longapertites with pteridophyte spores and fungal fruiting bodies confirm the prevalence of tropical to subtropical climate during the deposition of the sediments sesquiterpenoids like longifolene 12 methanoazulene cadinane and selinene together with amyrin derivatives are the indicator of dipterocarpaceae family that grows in the extant tropical rain forests in se asia appearance of dinoflagellate cysts and the predominance of lower molecular weight part in n alkane series with the signature of submerged floating vegetation in the shale horizon indicate marine influence in the younger part of the mine section the presence of mangrove pollen such as spinizonocolpites proxapertites and acanthotricolpites further suggests that the lignite bearing sequence was deposited in marshy marginal marine environment

aliphatic and aromatic triterpenoid hydrocarbons in a tertiary angiospermous lignite abstract the hydrocarbon biomarker assemlage of a liptinite rich early tertiary angiospermous lignite has been characterized the biomarker fistribution for the lignite confirms the low maturity and previous paleobotanic interpretations the aliphatic hydrocarbon fraction consists predominantly of n alkanes showing a strong odd carbon predominance and numerous de a triterpenoids and triterpenoids derived from higher plants bacterially derived triterpenoids were represented primarily by homohopanes and hopenes the aromatic hydrocarbon fraction contains a series of mono di and triaromatic de a triterpenoids and mono tri and tetraaromatic triterpenoids derived from higher plants the concentration and abundance of monoaromatic triterpenoids containing one to three additonal degress of unsaturation have not seen previously observed in a single deposit as such a diagenetic scheme for angiosperm derived triterpenoids is presented which confirms and extends previous hypothesis

testing clumped isotopes as a reservoir characterization tool a comparison with fluid inclusions in a dolomitized sedimentary carbonate reservoir buried to 2 4 km constraining basin thermal history is a key part of reservoir characterisation in carbonate rocks conventional palaeothermometric approaches cannot always be used fluid inclusions may be reset or not present while 18o palaeothermometry requires an assumption on the parent fluid composition the clumped isotope palaeothermometer however is a promising technique for constraining the thermal history of basins in this study we test if clumped isotopes record temperatures of recrystallisation in deeply buried dolomitic reservoirs through comparison with fluid inclusion data the studied reservoir is the cretaceous pinda formation offshore angola a deeply buried dolomitised sedimentary carbonate hydrocarbon reservoir it provides an ideal test case as samples from industry wells are available over a relatively wide burial depth range of 2000 4000 metres below sea floor mbsf and the constituent dolomites are relatively homogeneous across this depth range fluid inclusion homogenisation temperatures for the pinda formation record a range of temperatures from 110 170 c increasing with depth these closely match present day ambient well temperatures indicating recent resetting of the fluid inclusions clumped isotopes however record temperatures significantly 20 60 c below fluid inclusion and well temperatures for the seven samples analysed the deepest five samples 2800 3700 mbsf record clumped isotope temperatures around 100 120 c interpreted to represent a deep burial recrystallisation event responsible for a massive re dolomitisation of the reservoir the lower clumped isotope temperatures 65 and 82 c of the shallower 2055 and 2740 mbsf samples are interpreted to represent physical mixing of two dolomite generations due to incomplete burial recrystallisation of an early shallow dolomite determination of temperature through clumped isotopes allows calculation of the parent fluid 18o values in the five deepest samples the fluid 18o values of 3 7 6 5 cluster around the modern day porewater composition 5 suggesting burial dolomitisation occurred in the presence of evolved brine mineral 18o values of 4 5 to 7 are lower than pristine cretaceous marine dolomite and are in accordance with burial recrystallisation clumped isotopes are therefore interpreted to record temperatures corresponding to open system burial recrystallisation events this study shows that clumped isotopes are a valuable tool in characterising the thermal history of deeply buried 2000 m carbonate hydrocarbon reservoirs

palaeoenvironment assessment of pliocene lom lignite bulgaria from bitumen analysis and preparative off line thermochemolysis abstract the dacian coal bearing province is located in nw bulgaria coal formation is thought to be connected with desiccation of the dacian basin during a prolonged regression in the late pontian and pliocene dacian romanian age a lom lignite sample was characterized via micropetrography bulk chemical analysis spectral methods and thermochemolysis the pollen record was poor suggesting coal formation under oxygen rich conditions during peatification straight chain alkanes alkan 2 ones alkanols des a triterpenoids aromatized triterpenoids aromatized hopane hopene hopanes and triterpenoids with a strong dominance of oleanane derived structures were present in the extracted bitumen the residue after extraction was subjected to preparative off line tetramethylammonium hydroxide tmah thermochemolysis the aliphatic products released were c22 c27 fatty acid fa methyl esters i e methoxymethyl esters c22 c28 even numbered diacids dimethyl esters with a smooth distribution and traces of i and ai c15 acid methyl esters trapped and bound fas were distinguished using tetraethylammonium acetate teaac treatment the main thermochemolysis products were phenols structurally related to lignin vanillyl and syringyl units were produced in similar amounts indicating nonwoody angiosperm vegetation as the main plant input to the palaeo swamp probably originating from marsh or grassland sources the bitumen provided unequivocal information for an angiosperm contribution to the mire while the results of the tmah pyrolysis revealed a concomitant angiosperm and gymnosperm input the biomarker assemblage makes the lom lignite unique in bulgaria all the other bulgarian neogene lignites being dominated by coniferous vegetation with only traces of angiosperm contributions

scotia sea regional tectonic evolution implications for mantle flow and palaeocirculation abstract the scotia sea and surrounding scotia arc have evolved over the past 40 ma by extension behind an east migrating subduction zone at the boundary between the south american sam and antarctic ant plates the considerable data set now available regional geology and geophysics earthquake seismology satellite altimetry global plate analyses suggest why east migrating subduction began what has been the driving force that has sustained it and what other processes have controlled the mode of back arc extension in the scotia sea a suite of six reconstructions has been developed based on this data set the reconstruction to 40 ma creates a compact cuspate continental connection between south america and the antarctic peninsula at the subducting pacific margin with fragments now dispersed around the scotia arc occupying positions within it compatible with their known geology the driving force has been subduction of south american ocean floor which began as a result of southward migration of the pole of south american antarctic plate rotation and a key modulator of back arc extension has been collision of ridge crest sections of the south american antarctic plate boundary with the east advancing trench cenozoic regional tectonic evolution has two other likely consequences which greatly increase its importance firstly this region saw the tectonic disruption of the final barrier to complete circum antarctic deep water flow that may have had a profound effect on palaeoclimate secondly it is possible that the rapid roll back of the hinge of subduction is related to shallow eastward flow in the sub lithospheric mantle both of these consequences are explored the reconstructions show that rapid roll back of the subduction hinge averaging 50 mm a over the last 40 ma with respect to the south american plate has been a feature of all of scotia sea evolution and provide a history of motion of several oceanic microplates most of which are now welded together within the scotia sea this will guide the location of seismometers and or dredge hauls to test the hypothesis of shallow mantle flow and help interpret the results the reconstructions also allow an assessment of the creation of deep water pathways that would have permitted the development of the present day antarctic circumpolar current acc an early miocene onset within the period 22 17 ma seems likely for the acc depending on the structure and palaeo elevation of davis bank and aurora bank sections of the north scotia ridge however the study shows there was a delay of one or more million years between initial provision of a deep water pathway and the major mid miocene change in global climate involving the general level of antarctic glaciation that may have been related if these changes were related then the delay suggests that other factors possibly rough elevated ocean floor but also non tectonic factors such as atmospheric co2 were important in determining palaeoclimate

coal and coal macerals as source rocks for oil and gas abstract the role of coals in the generation and migration of hydrocarbons is discussed from the viewpoints of chemistry and petrology extract data and considerations of volatile matter and maturity suggests that under geochemical conditions most coals can give rise to oil as well as gas a distinction is drawn between release of absorbed oil and formation of hydrocarbons by thermal breakdown of the coal matrix itself the generation and preservation of oil require not only that suitable lipidic structures be present but that the product oil can escape before being cracked to gas exinite preferably in large discrete particles is the most oil prone maceral vitrinite can form oil but subsequent migration depends on the availability of cracks and fissures in the coal matrix the most highly reflecting forms of inertinite e g fusinite have no inherent capacity to generate oil low reflectance inertinite such as is common in many australian coals may have minor source potential a speculative attempt is made to quantify the oil generating capacity of coal macerals and mixtures as a general broad rule on a weight basis exinite can produce ten times more oil than vitrinite and a hundred times more than inertinite approximate calculations suggest that thermal maturation of coals can account for all the known oil and gas reserves in the gippsland and cooper basins of australia even if only 1 of generated hydrocarbons is trapped

reconstruction of floral changes during deposition of the miocene embalut coal from kutai basin mahakam delta east kalimantan indonesia by use of aromatic hydrocarbon composition and stable carbon isotope ratios of organic matter the distribution of aromatic hydrocarbons and stable carbon isotope ratios of organic matter in a series of nine miocene embalut coal samples obtained from nine coal seams of kutai basin east kalimantan indonesia were studied the rank of the embalut coals ranged from lignites to low rank sub bituminous coals 0 36 0 50 rr based on measurements of huminite reflectance the aromatic hydrocarbon fractions of all coal samples were dominated by cadalene in the lower boiling point range and picene derivatives in the higher boiling point range of the gas chromatograms cadalene can be attributed to the contribution of dipterocarpaceae and various hydrated picenes to the contribution of additional angiosperms to the coal forming vegetation the picenes originate from alpha and beta amyrin however in some coal samples minor amounts of simonellite and retene were also detected which argues for an additional contribution of gymnosperms conifers to coal forming vegetation preferentially in the middle miocene and at the beginning of the late miocene the results of stable carbon isotope ratios d 13

provenance of late carboniferous sandstones in the pennine basin uk from combined heavy mineral garnet geochemistry and palaeocurrent studies abstract analyses of heavy mineral assemblages garnet geochemistry and palaeocurrent directions may each independently provide useful information on the provenance of sandstones but when such datasets are combined the number of options on the location of possible source areas can be greatly reduced also variations in heavy mineral signatures through a stratigraphical section can be explained in terms of switching between source areas rather than due to unroofing events in a single source area if palaeocurrent directions change at the appropriate levels likewise seemingly random changes in transport direction indicated by palaeocurrent variations through a short stratigraphical section can be shown by the heavy mineral data to be systematic and related to shifts between source areas illustrations of the mutual constraints provided by such combined datasets are drawn from late carboniferous successions of the pennine basin northern england where the contributions of detritus from several distinct source terrains and sediment pathways are well documented hallsworth c r morton a c claoue long j fanning c m 2000 carboniferous sand provenance in the pennine basin uk constraints from heavy mineral and detrital zircon age data sedimentary geology 137 147 185 chisholm j i hallsworth c r 2005 provenance of upper carboniferous sandstones in east derbyshire role of the wales brabant high proceedings of the yorkshire geological society 55 209 233 examples are given of how mineralogically distinct and geographically separated provenances can be identified how variations in heavy mineral suites can be used to identify whether variations in palaeoflow represent variations in provenance and how localised mixing recycling in incised channels can be inferred the final example defines the regional extent of the widespread northerly derived fluvial yeadonian sandstones and provides evidence for the mixing of more local sediment supplies at the basin margins

changes in hydrocarbon maturity indices with coal rank and type buller coalfield new zealand abstract the buller coalfield south island new zealand is an inverted late paleogene basin that contains middle eocene bituminous coals which exhibit considerable variation in both coal rank across basin and coal type in seam twenty two fractionated bitumen extracts of brunner coal measures coal samples from 12 drillholes were analyzed by gc and gc ms to characterize the effect of coal rank and type on conventional hydrocarbon maturity indices at the beginning and end of the oil window 0 56 1 26 ro max the carbon preference index pristane phytane and isoprenoid n alkane ratios evolve throughout the high volatile bituminous b rank stage while other biomarker ratios 18 h 22 29 30 trisnorneohopane 17 h 22 29 30 trisnorhopane ts tm 18 h 21 h 30 norneohopane c 29 ts 17 h 21 h 30 norhopane and c 30 diahopane hopane do not show appreciable change in value until medium volatile bituminous rank various aromatic based ratios appear to be more effective in delineating rank throughout the entire oil window in particular the methylphenanthrene index and vitrinite reflectance are positively correlated over the entire bituminous rank range however subtle changes in depositional conditions variable coal type complicate these rank estimates within a given coal seam variation in cpi isoprenoid n alkane and hopane sterane ratios appear to be related to the hydrogen content of the coal while the homohopane index and the oleanane hopane ratio covary with sulfur content as with depressed vitrinite reflectance values mpi is similarly lowered in the perhydrous samples the mechanisms that control these hydrocarbon parameters during deposition and diagenesis are complex and convoluted however changes in bacterial activity and community with marine incursion appear to play an important role due to these anomalies none of the hydrocarbon maturity indices calculated can be singularly used to constrain coal rank

distribution of aliphatic des a triterpenoids in the dajiuhu peat deposit southern china abstract aliphatic des a triterpenoids have been tentatively assigned in samples taken from a 260 cm thick peat sequence from the dajiuhu basin of southern china using gas chromatography mass spectrometry gc ms the compounds possessing the carbon skeletons of oleanane ursane or lupane are generally considered as the microbial degradation products of plant triterpenoids under anoxic conditions abundant aliphatic des a triterpenoids were observed only in peat samples during the transitional period from the last glaciation to the early holocene 9 5 11 6 cal 14 c ka bp among these des a lupane is the only saturated ring a degraded compound whilst mono and di unsaturated des a triterpenes are dominated by oleanane and ursane derivatives the mono and di unsaturated des a triterpenes show a strong correlation r 2 0 94 in abundance indicating that they may be derived from the same source or process des a lupane shows no correlation in abundance with the mono or di unsaturated des a triterpenes r 2 des a triterpenoids corresponds to the interval with relatively high sedimentation rate 0 3 mm per year these data indicate that the abundance of aliphatic des a triterpenoids in the dajiuhu peat deposit in the early holocene may result from the prevailing reducing conditions in the water table or surficial sediment and or rapid preservation of the early diagenetic products our study highlights the potential application of des a triterpenes in the reconstruction of palaeoenvironments based on peat sequences

timing and climatic consequences of the opening of drake passage age estimates for the opening of drake passage range from 49 to 17 million years ago ma complicating interpretations of the relationship between ocean circulation and global cooling secular variations of neodymium isotope ratios at agulhas ridge southern ocean atlantic sector suggest an influx of shallow pacific seawater approximately 41 ma the timing of this connection and the subsequent deepening of the passage coincide with increased biological productivity and abrupt climate reversals circulation productivity linkages are proposed as a mechanism for declining atmospheric carbon dioxide these results also indicate that drake passage opened before the tasmanian gateway implying the late eocene establishment of a complete circum antarctic pathway

provenance of eastern magallanes foreland basin sediments heavy mineral analysis reveals paleogene tectonic unroofing of the fuegian andes hinterland abstract documenting variations in the composition of foreland basin detrital sediments is a useful tool for reconstructing the kinematic history of associated orogenic systems herein we report the results of our sem eds heavy mineral analysis of the late cretaceous to early miocene eastern magallanes basin of southernmost argentina our data indicate that campanian to middle eocene sediments had a mafic ophiolitic provenance which we interpret as being derived from the patagonian fuegian magmatic arc and the mafic floor of the preceding rocas verdes marginal basin upper middle eocene to lower miocene heavy minerals on the other hand indicate a metamorphic metasedimentary provenance which we interpret as being derived from the cordillera darwin metamorphic complex together these data indicate an abrupt shift in sediment provenance in middle to late eocene time thereby corroborating recent interpretations of the basin s detrital zircon geochrononology and providing further support for temporal and possibly genetic relationships between development of the patagonian orocline the opening of drake passage and the oi 1 glaciation of antarctica

organic geochemistry and petrography of tertiary coals and carbonaceous shales from argentina a series of eight tertiary coal and carbonaceous shale samples with vitrinite reflectance values between 0 50 and 0 58 were extracted fractionated and the saturated and aromatic hydrocarbons analysed for characteristic components by gc and gc ms additionally a microscopical study was undertaken in order to obtain a more precise picture of the samples under investigation the saturated hydrocarbon fractions displayed the typical n alkane distribution for coals of this rank with cpi values between 2 0 and 3 1 among the branched cyclic compounds pristane and homohopane were recognised as relevant components pointing to an oxic depositional environment detection of benzohopanes c32 c35 in the aromatic hydrocarbon fractions suggests that bacteriohopanetetrol was a significant constituent of the coal biomass taking into consideration the pr ph ratios ash contents and microscopical characteristics of the samples aspects of the possible degradation of hopanetetrol to homohopane are discussed resin derived diterpenoids with the phyllocladane and kaurane skeleton were tentatively identified and although minor compounds they are interpreted to be a sign of the contribution of podocarpaceae and araucareaceae to the coal swamp aromatic compounds were dominated by alkylnaphthalene derivatives presumably formed by c ring cleavage and aromatisation of higher plant derived pentacyclic triterpenois which were main components in the high boiling range of the fractions investigated angiosperms especially fagaceae are postulated as source for these polycyclic compounds and hence for some of the polyalkylated aromatic bicyclics detected

chemostratigraphic evidence of higher plant evolution in the taranaki basin new zealand correlation between palynological and biomarker records of higher plant development during the cretaceous and paleogene in taranaki basin new zealand is good gymnosperms particularly podocarps were the chief members of coastal plain swamp flora during the late cretaceous and contributed significant quantities of diterpanes often dominated by isopimarane to organic rich sediments angiosperms increased in relative abundance through the paleocene and became the dominant higher plants in the eocene their contributions to coaly sediments are characterized by various triterpanes particularly 18 h oleanane and its c24 a ring degraded counterpart this change in dominance of higher plant groups can be followed by the use of an angiosperm gymnosperm index agi based on the relative concentrations of selected triterpanes and diterpanes in mz 191 and mz 123 mass chromatograms plant biomarker distributions do not provide as precise age indications as do pollen assemblages but they may be more representative of the vegetation growing in a particular area of a peat swamp

occurrence and palaeoenvironmental significance of aromatic hydrocarbon biomarkers in oligocene sediments from the mallik 5l 38 gas hydrate production research well canada abstract the aromatic hydrocarbon biomarker distributions of thirty oligocene sediment samples with different lithology lignite clay and sand from the japex jnoc gsc et al mallik 5l 38 gas hydrate production research well canada were analyzed using gas chromatography mass spectrometry gc ms the compositions vary with lithology indicating a change in palaeoenvironmental conditions at the time of deposition aromatic diterpenoids of the abietane type are more abundant in the lignite samples than in the clay samples and represent a gymnosperm e g conifer dominated palaeovegetation in contrast in the clay samples aromatic triterpenoids are generally preserved as major constituents indicating angiosperm dominated vegetation the sand samples contain only minor amounts of aromatic terpenoids but show a preference for diterpenoid gymnosperm markers to recognise gymnosperm versus angiosperm dominated palaeoenvironments a new ratio termed the angiosperm gymnosperm aromatic ratio agar has been developed thus the terpenoid distribution in the deltaic sediments provides information on the compositional changes in the plant community at the mallik site lignites and the hinterland clays over time concomitantly the changing dominance in the plant communities allows an insight into varying climatic conditions during the late oligocene in the area additionally the aromatic biomarker composition has been used to assess the level of thermal maturity of the organic matter in the mallik samples and indicates a prevailing immature character

a comparison of terpenoid and leaf fossil vegetation proxies in paleocene and eocene bighorn basin sediments abstract plant derived terpenoids long recognized as biomarkers can help reveal the major taxonomic groups of land plants present in ancient environments even if rocks and sediments do not preserve plant macro or microfossils previous studies have used simple di to triterpenoid ratios to reconstruct floral changes in the geologic past but few have compared terpenoid ratios with estimates of floral composition from fossils further reconstructions have not taken into account differences in biomarker production i e concentration relative to leaf biomass between different types of plants here we have examined terpenoids from early cenozoic fluvial rocks from the bighorn basin wyoming usa where fossil flora has been studied in detail we analyzed the distributions of diterpenoids triterpenoids and n alkanes from leaf wax in a total of 43 samples from 15 stratigraphic horizons of late paleocene 63 ma to early eocene 53 ma in age in nearly all samples triterpenoids derived from angiosperms were significantly lower in abundance than conifer specific diterpenoids a finding that contrasted with plant fossil evidence for the same rocks this suggests that di to triterpenoid ratios severely underestimate the abundance of angiosperms in paleovegetation angiosperms dominated n alkane production among modern plants and we propose a new paleovegetation proxy based on the ratio of diterpenoids conifers to n alkanes angiosperms corrected for lipid production estimated from extant vegetation using diterpenoids and alkanes we infer the composition of paleovegetation to be similar to that inferred from plant fossils although the approach works well for the bighorn basin we stress the new paleovegetation proxy will need to be evaluated for other time periods communities paleogeography and depositional environments with pollen or megafossil data available