biomarker maturity parameters for high maturities calibration of the working range up to the oil condensate threshold abstract in a study of oils and source rocks from the kimmeridge clay united kingdom and the hanifa qatar formations several biomarker maturity parameters with working ranges up to vr e vitrinite reflectance equivalent 1 0 oil condensate threshold have been identified and calibrated this represents a significant improvement compared to commonly used biomarker maturity tools sterane and hopane isomerisation with their maturity maximum of approximately vr e 0 7 early part of oil window these new parameters are 1 the absolute concentrations of steranes and hopanes decreasing gradually with increasing maturity 2 the ratio of tricyclic terpanes tricyclic terpanes hopanes increasing with maturity 3 the ratio of diasteranes 14 h 17 h steranes depending both on maturity and on source rock lithology and 4 the ratio of t s t m 22 29 30 trisnorneohopane 22 29 30 trisnorhopane increasing rapidly at very high maturities during artificial maturation experiments the biomarker maturities described in the natural samples were also known to be time temperature dependent up to rather severe laboratory heating conditions this corresponds with the working range up to high maturity levels as observed in the natural samples

organic geochemistry in a sequence stratigraphic framework the siliciclastic shelf environment of cretaceous series se france for a better understanding of siliciclastic shelf environments correlation between sequence stratigraphy and organic geochemistry is used our study is focused on the cretaceous deposits of marcoule gard france particularly on a close packed siltites layer 200 400 m thick which is well characterized as a marine flooding facies of a single trangressive regressive cycle during the uppermost albian and the lower cenomanian the stratigraphic data indicate a change in the depositional environment from offshore to shoreface organic geochemistry is used in order to characterize origin and variability of the organic matter in relation to the stratigraphic data the study is carried out on core samples from 2 drill holes mar 203 and mar 501 analyses of the aliphatic and aromatic hydrocarbons were performed using gc ms and focused on biomarker distributions the biomarkers indicate a contribution of mixed terrestrial and marine organic matter the changes in molecular signatures are related to variations in the source of organic matter marine versus terrestrial preservation conditions largely influenced by clay and early diagenesis environmental oxidation reduction and acidic conditions as well as bioturbation various environmental zones characterized by different molecular signatures can be distinguished resin derived biomarkers can be assigned to higher plant material input and may reflect the evolution and diversity of gymnospermae versus angiospermae during the transgressive regressive cycle the relative sea level variations are clearly correlated with the nature and the preservation of the organic matter for example the pr ph and pr n c 17 ratios as well as the regular steranes distributions underline the maximum flooding surface evidenced by other studies we observe a good correlation between the organic data and sequence stratigraphy changes in geochemical signatures reflect the 3rd order depositional cycles

the microbial input in carbonate anhydrite facies of a sabkha palaeoenvironment from guatemala a molecular approach abstract nine representative rock samplesincluding four anhydrites an oil stained dolomite and a laminated mudstone source rock from a sabkha type palaeoenvironment la felicidad 1 well guatemala have been compared in order to tentatively characterize each facies by a geochemical signature each sample has been studied by using basic parameters toc rock eval pyrolysis yields and analyses of alkanes and aromatics by computerized gc ms the following families of compounds have been reviewed n alkanes branched and cyclic alkanes n alkylbenzenes benzohopanes monoaromatic steroids d ring aromatic 8 14 secohopanoids alkylnaphthalenes alkylphenanthrenes alkyldibenzothiophenes and triaromatic steroids despite close geochemical relationships of all the sample a more in depth investigation taking into account molecular patterns and semi quantitative data reveals significant differences among the samples anhydrites may be differentiated from carbonates which illustrates the efficiency of organic geochemistry in environmental palaeoreconstruction even in organiccarbon lean sediments toc 0 04 0 08 in anhydrites in these anoxic marginally mature sediments the strong predominance of triterpanes over steranes tt to st 20 associated with other molecular features leads to the conclusion that the main contribution to the organic matter of all facies is by bacteria several prominent components including novel families iso c23 and iso c27 alkanes tetracyclic terpanes d ring aromatic 8 14 secohopanoids 1 phenylpentadecane undecylnaphathalene and their mono and dimethylated counterparts have been interpreted as derived from halophilic bacteria these conclusions may be extended to all crude oils from the same area which may be considered as true bacterially derived petroleums the la felicidad 1 well data are discussed with reference to other palaeosabkha type sequences from the sw aquitaine basin france in which the bacterial input is less important however in these sabkha sequences 1 phenylpentadecane undecylnaphthalene and related structures have also been identified

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

paleoenvironmental characterization of a jurassic sequence on the bombarral sub basin lusitanian basin portugal insights from palynofacies and organic geochemistry abstract a middle upper jurassic sedimentary succession has been cut by the ramalhal 1 borehole in the bombarral sub basin lusitanian basin portugal the succession comprises the brenha montejunto abadia and lourinha formations which are composed of limestones marls sandstones and clays the main objective of this study was to characterize the organic matter using palynofacies and geochemical analyses to determine the depositional paleoenvironments and the hydrocarbon generation potential the total organic carbon content is generally less than 1 wt but reaches 4 1 wt in one sample due to the presence of perhydrous coal the rock eval pyrolysis results reveal lower values hi usually nether to 100 mghc gtoc showing that the studied samples have type iii kerogen and a low potential for oil generation the t max values varies between 319 and 443 c and biomarker data obtained for these samples indicate a maturation ranging between immature and eventually mature the palynofacies data indicate predominance of the phytoclast group 80 with different degradation degrees and a modest contribution of palynomorph group especially sporomorphs and the amorphous organic matter aom group solid bitumen was observed in some samples from the montejunto and brenha formations determining the relative percentages of the kerogen groups allowed for the identification of seven intervals that established variations in the depositional environment

water column euxinia and wildfire evidence during deposition of the upper famennian hangenberg event horizon from the holy cross mountains central poland a palynological study of the uppermost famennian section from kowala quarry holy cross mountains central poland allowed recognition of two miospore zones lv retispora lepidophyta apiculiretusispora verrucosa and ln retispora lepidophyta verrucosisporites nitidus based on palynology and sedimentology the black shale within the upper part of the section is identified as equivalent to the hangenberg black shale which is known globally this black shale contains compounds characteristic of photic zone euxinia including isorenieratane and its derivatives such compounds are absent in the organic poor marls and shales occurring below the ln zone and are present only as traces in the layers just above the black shale indicating fluctuations in the oxygen minimum zone during uppermost famennian sedimentation palynofacies show high amounts of amorphous organic matter and prasinophyte concentrations in the black shale and a subsequent significant decrease of amorphous organic matter concomitant with a rapid increase of terrestrial input mainly miospores with common tetrads in the layers above the black shale this supports the relatively rapid change in the taxonomic composition of phytoplankton caused by fluctuations of the chemocline the whole succession corresponds to one sea level rise and fall the presence of high concentrations of peri condensed polycyclic aromatic hydrocarbons and large amounts of small charcoal particles at the hangenberg event horizon indicate the occurrence of wildfires such observations suggest that atmospheric o2 levels had exceeded the critical threshold of 13 above which wildfires may occur by latest famennian time

frasnian famennian biotic crisis undervalued tectonic control the prime cause of the late devonian kellwasser crisis culminating in a mass extinction event near the frasnian famennian f f boundary remains conjectural nevertheless rapid sea level fluctuations of uncertain origin during tectono eustatic highstand paired with repeated oceanic anoxia and climatic changes are usually thought at present to be one of the main immediate triggers the cathles hallam model of stress induced changes in plate density accompanying rapid rift formation furnishes an alternative for understanding the enigmatic sudden eustatic variations in the non glacial time late devonian tectonic extension causing rifting and volcanicity appears to be strongly marked in several regions of eurasia particularly in kazakhstan and eastern laurussia all larger devonian continents were more or less tectonically affected a subtle record of this tectonic rearrangement is implied even for distant and apparently quiet carbonate platforms in local extensional block faulting and tilting hydrothermal mineralisation geochemical anomalies and localized blooms of siliceous biota interpreting the late frasnian regressive transgressive pattern in terms of the cathles hallam tectono eustatic model two major rifting events are hypothesized one at about the beginning of the rhenana zone and a second principal pulse in the late linguiformis zone that encompassed the f f transition developing the veimarn milanovsky scenario of the global extensional pulse it is assumed that the key endogenous factors were related to episodic super plume activity the tectonically triggered changes climaxed in thermal and nutrient pulses and induced the stepdown ecosystem destabilization observed in the f f bio crisis minor cometary strike s might have eventually participated in this prolonged multicausal environmental stress mainly due to additional thermal shocks but perhaps effective on a regional scale only

influence of palaeoweathering on trace metal concentrations and environmental proxies in black shales the mineralogical and chemical compositions of lower carboniferous tournaisian marine black shale from the kowala quarry the holy cross mountains poland were investigated this study focuses on disturbances in palaeoenvironmental proxies caused by palaeoweathering which progressively changed the major and trace element abundances palaeomagnetic investigations reveal that the devonian carboniferous succession was weathered during the permian triassic by the infiltration of oxidizing fluids related to karstification following post variscan exhumation the weathering process led to vermiculitization of chlorite partial dissolution of calcite and replacement of pyrite by hematite and goethite moreover the concentrations of some trace metals including co cu pb mo ni as and u significantly decreased consequently some elemental abundance ratios that are used as environmental proxies including u th ni co and v cr were altered elements that are bound to iron sulphides e g mo appear to be especially prone to mobilization by even a lightly weathered black shale the documented weathering including changes in elemental concentrations can potentially create misinterpretations of the original palaeoenvironmental conditions in addition the palaeoweathering of the studied samples appears to have substantially changed the carbon oxygen nitrogen and molybdenum stable isotope values the nitrogen and molybdenum stable isotope ratios in particular appear to be most sensitive to the effects of weathering and therefore are good indicators of palaeo weathering processes the major cause of these changes is the decay of organic matter and pyrite for the organic carbon stable isotopes ratios the main factor that controlls this process appears to be the preferential degradation of labile organic matter a combination of the total organic carbon toc total sulphur ts content mo concentration and stable isotope compositions seems to be the most useful for identify palaeo weathering our results suggest that reductions in ts and mo in tandem with diminished mo stable isotope values in the absence of obvious changes to the toc content provide the most compelling evidence of palaeo weathering

response of a late miocene mediterranean reef platform to high frequency eustasy the upper miocene reef complex of mallorca a third order depositional sequence shows how carbonate deposition responds to high frequency sea level cycles this reef complex displays a fractal architecture of hierarchically stacked high frequency units from fourth to seventh order the building blocks are sigmoidal units bounded by unconformities not parasequences these sigmodds are stacked in sets of sigmoids the sets are stacked in cosets and these in turn are stacked in sets of cosets all these accretionary units have characteristics of depositional sequences but differ from the model developed by exxon and from other carbonate sequence stratigraphy models these departures result from changes in carbonate production in relation to sea level fluctuations which determined the changes in accommodation in the absence of significant subsidence all these high frequency sequences are composed of four systems tracts 1 a lowstand systems tract formed during the early rise of a sea level cycle and composed of progradational reef to open shelf facies thinning toward the basin 2 an aggrading systems tract formed during sea level rise and composed of thick lagoon to open shelf deposits without landward shift of facies 3 a highstand systems tract formed during the high part of a sea level cycle and composed of progradational reef to open shelf facies thinning toward the basin with lagoon beds thin or absent and 4 an offlapping systems tract formed during sea level fall and composed of thin downlapping reef facies passing into a condensed open shelf section which correlates with an erosion surface on the platform top two bounding surfaces can be recognized by lithofacies changes between these systems tracts the erosion surface on top of the offlapping systems tract and the downlap surface at its base both surfaces merge basinward into a condensed section the sequence boundary which corresponds to the lowest point of the sea level cycle is the erosion surface landward and within the correlative condensed section basinward

relationship between petroleum composition and depositional environment of petroleum source rocks crude oils of nonmarine source can be distinguished from those of marine shale source and from oils originating in marine carbonate sequences by using a battery of geochemical parameters as demonstrated with a sample suite of nearly 40 oils a novel parameter based on the presence of c30 steranes in the oil was found to be a definitive indication of a contribution to the source from marine derived organic matter a second novel parameter based on monoaromatized steroid distributions was effective in helping to distinguish nonmarine from marine crudes and can be used to gauge relative amounts of higher plant input to oils within a given basin sterane distributions were similarly useful for detecting higher plant input but were less effective than monoaromatize steroid distributions for making marine versus nonmarine distinctions concentrations of high molecular weight paraffin can also be effective nonmarine indicators but are influenced by maturation and biodegradation processes certain algal derived nonmarine oils may show little high molecular weight paraffin response oils from carbonate sources with a few exceptions can be distinguished by having low pristane phytane ratios low carbon preference indexes and high sulfur contents gammacerane indexes and carbon isotope ratios of the whole crude are not effective in distinguishing these types of environmental differences on a global basis

characterization of organic matter in late cretaceous black shales of the eastern alps kainach gosau group austria abstract bituminous marls occur at the base of the late cretaceous kainach gosau basin eastern alps they interfinger with local coaly layers and are overlain by a turbiditic sequence forty outcrop samples with different lithologies were studied by rock eval pyrolysis seven bituminous marls one coaly sample two siltstones from the turbiditic sequence and solid bitumen from the paleozoic basement have been characterized in detail by organic geochemical and petrographic techniques the organic matter from bituminous marls can be subdivided into allochthonous terrigenous material mainly recycled vitrinite which is present in all samples in similar amounts and autochthonous hydrogen rich organic matter alginite liptodetrinite which is most probably of lacustrine origin organic richness varies from 0 4 to 2 3 toc the amount of the autochthonous organic matter is controlled primarily by different oxygen concentrations sedimentological lack of bioturbation and geochemical data e g pristane phytane ratios homohopane indices c 30 c 29 ts ratios distribution of phenol and alkylphenols in the pyrolyzate suggest that the water column above the sediment surface was suboxic to dysoxic but probably not anoxic high energy events were responsible for short periods with enriched oxygen in the water column the organic matter in the resulting sediments is of a residual type drift wood was transported from the nearby shore into the lake paleontological evidence proves a temporary marine influence vitrinite reflectance and tmax indicate maturation levels ranging from the beginning to the peak stage of oil generation despite the fact that some hydrocarbons have already been generated hi values of kerogens of bituminous marls reach 605 mg hc g toc most analysed bituminous marls produce a high wax paraffinic oil during maturation and are good sources for oil pyrolysis gas chromatography and biomarker data indicate that changing wax contents of oils generated from bituminous marls might be a function of different oxygen concentrations in the water column coaly samples have a very good gas potential

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

lacustrine shales and oil shales from stellarton basin nova scotia canada organofacies variations and use of polyaromatic hydrocarbons as maturity indicators abstract the post acadian stellarton basin is a small pull apart basin in northern nova scotia the coal brook member which is the main focus of this study contains the thickest and most extensive development of oil shales within the late carboniferous stellarton formation bulk and molecular geochemistry indicate that the organic rich oil shales and black shales contain type i ii kerogen with a mixed assemblage of aquatic and terrestrial organic matter that is dominated by the former biomarker evidence indicates that these sediments were deposited under deep anoxic and fresh to brackish water lake conditions organofacies distinctions were made on the basis of several parameters that are independent of maturity and therefore suggest organic matter changes the organofacies identified are the result of water level fluctuations that are climate controlled all of the aromatic compounds evaluated as maturity parameters were seen to experience alterations in proportion to temperature in the form of either depth or geologic age that can be correlated with maturity these alterations are believed to result from changes in molecular composition maturity parameters based on the alkylbenzothiophenic and alkylnaphthalenic compounds are shown to be effective maturity parameters in lacustrine sequences particularly over the higher maturity ranges where standard maturity parameters based on steranes and hopanes are not effective

concentrations of silicified cephalopods within upper frasnian carbonate concretions from the holy cross mountains poland abstract concentrations of silicified juvenile cephalopods from upper frasnian carbonate nodules from the ja wica quarry in the holy cross mountains are described here for the first time using conodonts the age of the investigated cephalopod rich nodules has been determined as the linguiformis conodont zone and may correspond to the upper kellwasser event the concentrations of silicified juvenile ammonoids described here resulted from a combination of biological and physical factors related to environmentally driven mass mortality induced by storms and perhaps additionally by anoxia following mass spawning and post mortem transport with the aid of bottom currents which enabled them to drift to small depressions on the sea floor rapid silification led to excellent preservation of the fossil assemblage

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

degradation and maturity controls on oil field petroleum column heterogeneity in the gullfaks field norwegian north sea abstract a geochemical mapping of the gullfaks reservoir petroleum column based on 226 reservoir core extracts and 23 drill stem test dst and repeat formation test rft oil samples indicates the presence of statistically testable lateral compositional heterogeneities in the petroleum column these different petroleum populations can be related to lateral filling of the field from two source basins and a more pervasive subsequent episode in reservoir biodegradation petroleum maturity gradients within the field were detected using conventional biomarker gc ms methods on saturated hydrocarbon fractions the degree of biodegradation was monitored by quantitative gc of n alkanes in whole oil samples using a squalane internal standard the observed compositional differences in the gullfaks petroleum column are consistent with diffusion being the primary mixing process thermal convection being eliminated on both compositional and modeling grounds compositional differences between core extracts and dst samples from the same intervals suggest that fractionation of petroleum might occur during testing and that interpretation of reservoir petroleum columns from mixed sample sets should be treated cautiously

distinctive hydrocarbon biomarkers from fossiliferous sediment of the late proterozoic walcott member chuar group grand canyon arizona abundant extractable hydrocarbons in association with well preserved kerogen have been recognised in a dolostone from the chuar group approx 850 ma the biomarkers present include c15 c30 acyclic isoprenoids c26 c28 steranes c27 c35 hopanes and extended tricyclic terpanes among the striking characteristics of the distributions are the dominance of steranes and methyl steranes lacking side chain alkylation and the presence of putative c29 c35 neohopanes and gammacerane the high abundance of steranes is consistent with the presumed eukaryotic affinities of several types of microfossils including chuaria present in associated mudstones this stratum is the oldest in which gammacerane has been found and suggests contributions from protozoa to the depositional environment which appears to have been hypersaline there is a strong correlation between the carbon isotopic composition of the kerogen and that of the various polarity fractions of the bitumens chemical degradation and pyrolysis of the kerogens yielded n alkanes with similar characteristics to the bitumens but there are differences in the patterns of distribution of the acyclic isoprenoid sterane and triterpane biomarkers

characterization of model evaporitic environments through the study of lipid components abstract a saline circuit has been studied as a model of coastal evaporite system the lipid composition of diverse salt ponds encompassing calcite gypsum and halite domains has been determined most of the lipid materials has been found in the carbonate samples and is related to algal cyanobacterial debris lipids in the gypsum domain are of heterotropic microbialorigin and extreme halophilic bacteria constitute the main lipid contribution in the halite samples n alkane distributions with high predominance of n docosane constitute a previously described feature of sedimentary evaporitic conditions that is charateristics of the intermediate calcite gypsum samples in the calcite domain the presence of c20 highly branched isoprenid olephines tetrahymanol and the large amounts of phytol constitute likely precursors of lipids usually found in evaporitic environments i e c20 highly branched isoprenoid alkanes gammacerane and high phytane pristane ratios their occurence point to dehydration and hydrogenations as two main diagenetic processes leading to the formation of evaporitic molecular markers

the mesozoic cenozoic organic facies in the lower tagus sub basin lusitanian basin portugal palynofacies and organic geochemistry approaches abstract studies of the mesozoic and cenozoic sequence crossed by the barreiro 4 borehole provide an improved understanding of the organic matter deposited in the lower tagus sub basin lusitanian basin portugal and the implications for the potential source rock and depositional environment this study focused on 43 samples middle jurassic to neogene that were subjected to palynofacies and organic geochemistry analyses total organic carbon rock eval pyrolysis and molecular biomarker analysis the palynofacies data indicate that the sequence contains mainly phytoclasts non opaque phytoclasts however the middle jurassic samples are dominated by amorphous organic matter aom continental and or marine palynomorphs are present in all the samples the cretaceous samples are characterized by small amounts of kerogen that have high contents of solid bitumen the total organic carbon toc content is generally less than 1 wt the rock eval s1 and s2 parameters vary from 0 01 to 3 50 mghc g rock and 0 15 to 34 03 mghc g rock respectively with the highest values corresponding to the cretaceous samples the hydrogen index hi and oxygen index oi values range from 35 to 552 mghc g toc and 4 to 180 mghc g toc respectively the tmax values range from 416 to 437 c the biomarker analysis showed that n alkanes with 15 30 carbon atoms are present and usually have a unimodal distribution with a predominance of low to medium molecular weight compounds the cpi values range between 0 63 and 3 65 and the pristane phytane ratios vary between 0 48 and 1 64 indicating alternation of oxic anoxic conditions along the sequence the distribution of terpanes shows small amounts of tricyclic and tetracyclic terpanes in most of the samples except for some cretaceous samples and a predominance of pentacyclic terpanes the amount of 17 h 22 29 30 trisnorhopane tm usually exceeds the amount of 18 h 22 29 30 trinorneohopane ts the 20s 20s 20r and ratios of the c29 steranes generally have values below the range of equilibrium indicating an immature stage of the om

significance of coniferous rain forests and related organic matter in generating commercial quantities of oil gippsland basin australia contrary to the conventional belief that humic coal generates primarily gas 3 billion bbl of recoverable oil has been discovered in the humic coaly succession of the fluviodeltaic latrobe group upper cretaceous tertiary that serves as both the reservoir and the source for hydrocarbons in the offshore gippsland basin of southeastern australia evidence for generation of liquid hydrocarbons from the coaly succession includes 1 similarity of n alkane distribution in the oil and in the coal extracts 2 high wax content of oil up to 27 by weight 3 high ratio of pristane phytane in oil 5 6 and 4 dominance of c29 steranes in the oil in the gippsland basin coniferous rain forests dominated by kauri vegetation flourished in a raised bog setting present temperate climate and kauri vegetation of new zealand are considered to be the modern analog to the gippsland basin the coniferous vegetation provided large quantities of hydrogen rich exinite macerals such as cutinite and resinite with potential to generate oil high rainfall raised ground water level low oxygen high acidity and low nutrient conditions of a raised bog setting were suitable for preserving organic matter a comparison of gas chromatograms of oils in the gippsland basin with gas chromatograms of oils generated by hydrous pyrolysis in the laboratory from the immature source rocks suggests that the paraffinic fraction of the oil was derived from coal and the naphthenic fraction was derived chiefly from resin

the drowning of a carbonate platform an example from the devonian carboniferous of the southwestern holy cross mountains poland the broad middle devonian carbonate platform of the holy cross mountains was fragmented during the frasnian and afterwards submerged as isolated blocks and transformed into a topographic depression the section exposed in the ostrowka quarry illustrates a well documented drowning of the last small fragment seamount of this carbonate platform which submerged during late devonian and early carboniferous times the recognized facies succession reflects a progressive stepwise lowering of the sediment surface through time from a peritidal lagoonal environment to a deep water anoxic basin the frasnian shallow water carbonate platform is represented by lagoonal facies with peritidal sediments small scale deepening upward cycles punctuated with emersion surfaces are a feature of this stage they resulted from a combination and continuous balance between carbonate production subsidence and low order eustatic sea level fluctuations the carbonate platform aggraded at rates around 100 125 m ma the shallow water peritidal carbonates are separated from the post platform deposits by an unconformity surface developed during subaerial exposure the flooding of the faulted block of galezice in the pre late marginifera time and the subsequent initial drowning resulted primarily from a rapid sea level rise small dimension of the seamount and its cemented upper surface were the most important factors that facilitated the sediment removal and thus suppressed the sediment accumulation a condensed section was deposited on the top of the seamount its stratigraphic succession and rare cephalopod storm beds account for a model of redistribution of sediment over the swell disintegrated by small scale faulting during drowning the seamount traversed down through the photic zone at an average rate not higher than 20 25 m ma transformation of the swell into a basin accelerated in the late tournaisian anchoralis zone it is manifested by an increase of deposition rate and by a lithology of alternating limestones and clays with participation of fine grained calciturbidites the associated tephra deposits and syndepositional ferruginous hydrothermal mineralization were the result of extensional tectonics on the facies evolution the drowning was completed in the visean with deposition of black siliceous shales in the starved basin the death of the devonian carbonate platform in the galezice area illustrates well the famed paradox of drowned platforms as the subsidence rate was much slower during the drowning than during the phase of the platform aggradation

is there evidence for a substantial contribution of prokaryotic biomass to organic carbon in phanerozoic carbonaceous sediments the role of prokaryotes bacteria and archaea in producing biomass and reworking settling and buried organic matter is of paramount importance since it exerts a major impact on the composition of sedimentary organic matter and ultimately petroleum this key role of prokaryotes in combination with a biomarker fingerprint often dominated by prokaryotic molecular fossils e g hopanoids has led to the assumption that prokaryotic biomass is a substantial source for organic carbon in carbonaceous sediments however biosynthesising and reworking organic matter does not necessarily imply sourcing organic matter by the prokaryotes and the abundance of biomarkers does not always reflect relative contributions to sedimentary organic matter in this paper the existing evidence for a substantial prokaryotic biomass contribution to sedimentary organic carbon oc is critically evaluated this shows that despite the often prominent presence of prokaryotic biomarkers in sediments evidence for a substantial prokaryotic contribution to sedimentary oc is generally lacking this is demonstrated by i the application of the carbon isotopic mass balance principle in various sedimentary settings ii an alternative explanation for the proposed dominant role of heterotrophic reworking in the oxford clay iii a summary of the effects of bacterial oxidation in organic matter rich turbidites and iv recent data showing that the evidence for recalcitrant carbon in prokaryotes is scant although these observations do not rule out substantial contributions of prokaryotic carbon to oc in phanerozoic carbonaceous sediments this remains to be demonstrated and the final answer awaits the development of new technologies to full characterise sedimentary oc

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

deciphering the upper famennian hangenberg black shale depositional environments based on multi proxy record abstract presented for the first time in this paper are the results of a detailed multi proxy investigation conducted on the hangenberg black shale hbs from the polish part of the laurussian shelf which provide details about the environmental conditions in existence during deposition of the shale and the role played by anoxic conditions in the mass extinction events that occurred at the end of the devonian times inorganic and organic redox indicators indicate that bottom water redox conditions changed periodically from being mainly anoxic euxinic to oxic or being partially depleted in oxygen u th values above 1 25 ni co values above 7 and v v ni values above 0 8 recorded from the lower part of the hbs all point to anoxic euxinic conditions being present as do high total organic carbon contents toc above 10 and degree of pyritisation dop values around 0 75 however the presence of benthic fauna over the lower part of the hbs attests to opportunistic colonisation of the seafloor during oxic episodes evidence for similar episodes has also been recognised over the middle part of the hbs e g u th values below 1 25 ni co values below 4 v v ni values below 0 8 toc values of 3 to 5 5 and dop values of 0 4 to 0 75 plus the common occurrence of benthic fauna anoxic conditions returned during the deposition of the upper part of the hsb though they were not as well developed as when the lower part of the shale was laid down of interest is the presence of small pyrite framboids and isorenieratene biomarkers in all the analysed samples which suggest that euxinic conditions persisted in the photic zone of the water column a twenty centimetre thick layer of volcanogenic deposits tuffites is present in the middle part of the hbs the geochemical characteristics of which are typical of ocean floor basalts the occurrence of volcanogenic material below and within the hbs together with an absence of calcium carbonate over its upper part the presence of abundant tetrads just above the black shale and a drastic decrease in faunal frequency in the upper part of the hbs imply that volcanism may have caused oceanic acidification or hypercapnia that in turn potentially may have influenced the hangenberg mass extinction event

biological markers in lacustrine chinese oil shales s u m m a r y a major objective in molecular organic geochemistry is the assessment and characterization of sedimentary depositional environments from the occurrence of specific biological marker compounds related to particular source organisms the aliphatic hydrocarbon distributions of petroleums and or sediments from chinese freshwater and hypersaline lacustrine environments are described and contrasted in the search for diagnostic features among their biological marker distributions the eocene maoming oil shale which crops out in guangdong province shows major differences in hydrocarbon composition through its stratigraphic succession these variations reflect changes in lithology and in the origins of the sedimentary organic matter as seen from petrographic examination the lower lignite and vitrinite layers contain significant contributions of biological markers from bacterial sources plus components derived from terrigenous higher plants such as c29 steroids in contrast the overlying shales show a dominance of dinoflagellate derived 4methylsteroids and culminate in an horizon with botryococcane homologues as their dominant alkanes thus the geochemical profile suggests that a swampy environment in which peats accumulated deepened to support populations of dinoflagellate and finally blooms of botryococcus green algae the aliphatic hydrocarbons of a series of sediments and petroleums from the eocene hypersaline sequence of the jianghan basin in southern hubei province shows various features that may be typical of such facies these include a dominance of even numbered n alkanes high amounts of phytane and gammacerane and an abundance of c35 hopanes similar characteristics are observed in shales from the eocene green river formation and in rozel point crude oil a petroleum thought to originate from sediments deposited under hypersaline conditions the same features also appear in a lower tertiary evaporitic mudstone from south of the renqui oil field in hebei province together with 4 methylsteranes fl carotane and 18c h oleanane a marker for terrigenous higher plants these data illustrate the potential of biological markers in the differentiation of different lacustrine environments and suggest that such characteristics may provide signatures for environmentally similar but geographically distant deposits

organic geochemical characterisation of depositional palaeoenvironments of source rocks and oils in brazilian marginal basins abstract an investigation of bulk isotopic and molecular features of a wide selection of source rocks and oils from brazilian marginal basins ranging from lower cretaceous to tertiary in age provides a number of organic geochemical criteria that characterise and distinguish their depositional palaeo environments the methods employed include evaluation of organic carbon contents rock eval pyrolysis vitrinite reflectance measurements determination of carbon isotope ratios elemental and visual kerogen analysis assessment of oils and solvent extracts by liquid and gas chromatography and quantitative biological marker investigations using gc ms for aliphatic hydrocarbons and uv vis spectrophotometry for metalloporphyrins selected data were evaluated using principal component analysis the results enable the recognition and differentiation of seven depositional regimes lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate marine deltaic marine highly anoxic with a predominance of calcareous mudstone lithology and marine anoxic with predominance of siliciclastic lithology diagnostic features in the biological markers from these depositional environments include the carbon number distributions of n alkanes pristane phytane ratios absolute concentrations of carotane higher acyclic isoprenoids c 30 hopane and steranes and the abundance of the latter relative to 4 methylsteranes the occurrence and abundance of particular biological markers such as gammacerane tricyclic and tetracyclic terpanes 18 h oleanane 28 30 bisnorhopane and 25 28 30 trisnorhopane and the relative abundances of nickel and vanadyl porphyrins

application of biological markers in the recognition of palaeohypersaline environments the hydrocarbon fractions of a marl sample from a messinian basin in the northern appenines and four oils rozel point oil utah and three seep oils from sicily were studied

origin of organic matter and paleoenvironment conditions of the late jurassic organic rich shales from shabwah sub basin western yemen constraints from petrology and biological markers abstract late jurassic organic rich shales from shabwah sub basin of western yemen were analysed based on a combined investigations of organic geochemistry and petrology to define the origin type of organic matter and the paleoenvironment conditions during deposition the organic rich shales have high total sulphur content values in the range of 1 49 4 92 wt and excellent source rock potential is expected based on the high values of toc 7 high extractable organic matter content and hydrocarbon yield exceeding 7000 ppm the high total sulphur content and its relation with high organic carbon content indicate that the late jurassic organic rich shales of the shabwah sub basin were deposited in a marine environment under suboxic anoxic conditions this has been evidenced from kerogen microscopy and their biomarker distributions the kerogen microscopy investigation indicated that the late jurassic organic rich shales contain an abundant liptinitic organic matter i e alginite structureless amorphous organic matters the presence of alginite with morphology similar to the lamalginite alga and amorphous organic matter in these shale samples further suggests a marine origin the biomarker distributions also provide evidence for a major contribution by aquatic algae and microorganisms with a minor terrigenous organic matter input the biomarkers are characterized by unimodal distribution of n alkanes low acyclic isoprenoids compared to normal alkanes relatively high tricyclic terpanes compared to tetracyclic terpanes and high proportion of c27 and c29 regular steranes compared to c28 regular sterane moreover the suboxic to anoxic bottom water conditions as evidenced in these late jurassic shales is also supported based on relatively low pristane phytane pr ph ratios in the range of 0 80 1 14 therefore it is envisaged here that the high content of organic matter toc 7 wt in the analysed late jurassic shales is attributed to good organic matter om preservation under suboxic to anoxic bottom water conditions during deposition

origin of organic matter from tectonic zones in the western tatra mountains crystalline basement poland an example of bitumen source rock correlation abstract solid bitumens of unknown origin found in brittle tectonic shear zones cutting the crystalline basement of the western tatra mts show uniform geochemical characteristics that suggest a uniform source for the original hydrocarbons on the basis of gc ms data a similarity between these solid bitumens and organic matter dispersed in the mesozoic source rocks of podhale trough and sedimentary cover of the northern tatra mts is observed the organic matter in the mesozoic source rocks shows a higher maturation level than that in the solid bitumens the molecular composition of the organic matter in both the solid bitumens and the basement rocks is significantly different from that in the paleogene sedimentary rocks infilling the podhale trough these immature to early mature paleogene sedimentary rocks contain organic compounds typical of terrestrial plants both conifers simonellite and retene and angiosperms lupane oleanane and taraxastene which are absent in the solid bitumens and in the mesozoic source rocks water co2 fluid inclusions in quartz sealing the shear zones have marine like salinity a dominance of cacl2 and mg2 depletion suggesting genetic affinity to dolomitised carbonate rocks such as potential middle triassic source rocks the low maturity of the solid bitumen in the shear zones relative to its mesozoic source can be explained by continued maturation of the mesozoic source rocks after expulsion and migration into the shear zones the results of hydrocarbon generation modeling indicate that oil expulsion from the mesozoic source rocks its migration through the shear zones and the subsequent maturation of the mesozoic source rocks all occurred within a short oligocene time interval

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

depositional environment and factors controlling β carotane accumulation a case study from the jimsar sag junggar basin northwestern china abstract a combined investigation of bulk geochemistry and molecular geochemistry was carried out on 31 source rock samples from the lower permian lucaogou formation in the jimsar sag of the junggar basin northwestern china geochemical characterization reveals the depositional environments and other factors favorable for the generation and accumulation of carotane an important hydrocarbon precursor many core samples have a total organic carbon content 1 and rock eval s2 values 2 mg hc g rock suggesting relatively high hydrocarbon generation potential biomarkers in the lucaogou source rock extracts are characterized by short to long chain n alkanes a wide range of pr ph ratios 0 74 1 42 and carotane index values carotane cmax 0 16 1 92 high concentrations of c29 sterane relatively low tricyclic terpane content and moderate gammacerane index values 0 14 0 29 this is consistent with a weakly oxidizing to weakly reducing depositional environment with fresh to brackish water conditions rapid input of terrigenous organic matter and a relatively small contribution of aquatic algal bacterial organic matter cross plots of biomarker parameters and the carotane index show that carotane in the lucaogou source rocks is mainly derived from terrigenous organic matter and is found predominantly in sediments deposited in weakly reducing brackish environments it does not appear to have been affected by thermal maturation

organic geochemistry and palynofacies of the early middle frasnian transition late devonian of the holy cross mountains southern poland abstract geochemical and palynological investigation of the lower to middle frasnian reef to basin succession at the well known kowala quarry holy cross mountains demonstrates the variable character of organic matter om deposited in different oxidative reductive conditions during sedimentation of the basinal deposits anoxic conditions in the water column prevailed in the organic rich sediments deposited during the palmatolepis punctata zone set d anoxia occurred in the photic zone as inferred from the presence of isorenieratane aryl isoprenoids and gammacerane in the same kind of deposits but occurring during the palmatolepis hassi zone set f anoxia apparently occurred mainly in the deeper parts of the basin and only sporadically reached the photic zone this interpretation is based on the lack of isorenieratane traces of aryl isoprenoids and the presence of gammacerane in the investigated samples the basinal clay enriched sediments of sets d and f are divided by an organic poor set e typical for the carbonate platform fore reef environment characterized by oxic conditions a palynostratigraphical study of the frasnian section from the kowala quarry allowed recognition of two miospore zones geminospora semilucensa perotrilites donensis sd and archaeoperisaccus ovalis verrucosisporites grumosus og relatively small quantitative and qualitative changes of the organic particles miospores tracheids prasinophytes and acritarchs are interpreted primarily in terms of sea level fluctuations and enhanced productivity in particular the appearance of abundant abnormally large mature leiospheres in set d can be the result of progressive eutrophication related to environmental changes recorded in the recently detected major positive carbon isotope anomaly as during the frasnian famennian mass extinction interval this eutrophication could have been stimulated by a rapid increase in primary production and subsequently expanding anoxic conditions but it is evident only in the early phase of the middle frasnian 13 c excursion the processes of the secondary hydrothermal fluid migration taking place after the lithification of the sediments caused partial om oxidation the products of these processes are such phenyl derivatives of aromatic hydrocarbons as phenylphenanthrenes terphenyls phenyldibenzothiophenes and phenyldibenzofurans moreover an oxygen compound rarely described from sedimentary om dibenzo p dioxin and its methyl and dimethyl derivatives seems to be the additional product of hydrothermal om oxidation

mechanism for the enrichment of organic matter in the liushagang formation of the weixinan sag beibuwan basin china abstract eocene lacustrine organic rich shales mudstones and shales in the middle member of liushagang formation designated as ls2 are the most important source rocks in the beibuwan basin located in the northwest of the south china sea in this study we explored the mechanisms responsible for the accumulation of organic matter in source rocks from ls2 of weixinan sag by investigating the paleoclimate paleoredox paleoproductivity and lithological characteristics of the parent rocks using biomarkers and elemental geochemistry data based on our analytical data the deposition of the source rocks from ls2 occurred in a warm humid paleoclimate with moderate chemical weathering as indicated by cia indexes and sr cu ratios the sr ba ratios and gammacerane indexes indicated that the source rocks from ls2 were deposited in a freshwater paleolake the corg p ratios and redox sensitive elements rses toc bivariate diagrams demonstrated that the organic rich shales and mudstones shales deposited under anoxic and oxic suboxic conditions respectively the levels of toc copper cu molybdenum mo and c30 4 methylsterance index in the organic rich shales were higher than those of the mudstones and shales indicating greater algae bloom and paleoproductivity during the deposition of the organic rich shales compared to during the sedimentation of the mudstones and shales combined with la yb ree sio2 tio2 al2o3 tio2 nb ta and cr co ratios it is considered that the parent rocks of the organic rich shales were granite of relatively intermediate lithological compositions with greater levels of nutrients such as phosphorus p mo cu compared to those of the mudstones and shales large scale decomposition of dead algae led to oxygen depletion which created favorable conditions for the preservation of organic matter and the release of p from the sediments to water the increased content of p in water subsequently aggravated algal blooms such a positive feedback loop was conducive to the formation of organic rich shales the inter relationships of algal blooms controlled by p paleoproductivity and paleoredox conditions play an important role in the accumulation of organic matter in organic rich shales from ls2 of weixinan sag beibuwan basin

the ratios of dibenzothiophene to phenanthrene and pristane to phytane as indicators of depositional environment and lithology of petroleum source rocks abstract the ratio of dibenzothiophene to phenanthrene and the ratio of pristane to phytane when coupled together provide a novel and convenient way to infer crude oil source rock depositional environments and lithologies such knowledge can significantly assist in identifying the source formation s in a basin thereby providing valuable guidance for further exploration the ability to infer this information from analysis of a crude oil is especially valuable as frequently the earliest samples in a new area may be shows and or drill stem test samples from exploratory wells which are characteristically drilled on structural highs stratigraphically remote from the source formation s a cross plot of dibenzothiophene phenanthrene versus the pristane phytane ratios measured on seventy five crude oils from forty one known source rocks ranging in age from ordovician to miocene consistently classified the oils into the following environment lithology groups marine carbonate marine carbonate mixed and lacustrine sulfate rich lacustrine sulfate poor marine and lacustrine shale and fluvial deltaic carbonaceous shale and coal the dibenzothiophene phenanthrene ratio alone is an excellent indicator of source rock lithology with carbonates having ratios 1 and shales having ratios the dibenzothiophene to phenanthrene and the pristane to phytane ratios can also be used to classify source rock paleodepositional environments the classification scheme is based on the premise that these ratios reflect the different eh ph regimes resulting from the significant microbiological and chemical processes occurring during deposition and early diagenesis of sediments the dibenzothiophene phenanthrene ratio assesses the availability of reduced sulfur for incorporation into organic matter and the pristane phytane ratio assesses the redox conditions within the depositional environment interpretation of these ratios has been aided by quantitative biomarker analysis and by carbon isotope data for pristane and phytane obtained by gas chromatography isotope ratio mass spectrometry

maturation sequence of continental crude oils in hydrocarbon basins in china and its significance abstract the continental hydrocarbon containing basins in china not only ubiquitously possess immature marginal mature oils as defined by c 29 sterane ratios but a complete oil maturation sequence can also exist the present paper studies the characteristics of immature oils their formation and distribution the study revealed that immature oils were not thermal degradation products of kerogen since the vitrinite reflectance r o of source rocks is between 0 4 and 0 6 the immature oils are derived from the soluble in organic solvent organic matter generated during low temperature hydrocarbon generation at the late stage of diagenesis the immature oils in china belong to paraffin base oils which originated from aquatic or terrestrial lipids but not resins the maturation sequence of oils is composed of immature low mature and high mature members corresponding to the different levels of hydrocarbon generation the recognition of this evolution sequence has proved to be of practical significance when we understand the amounts of oil reservoirs of different maturation the exploration direction can be guided by the corresponding resource volume comparison taking the qaidam basin as a good example most of the oils discovered recently are low mature but there are good prospects of finding mature and high mature oils

geochemical characterization and depositional environment of source rocks of small fault basin in erlian basin northern china abstract a combined investigation of molecular geochemistry elements and carbon isotopic composition of carbonate distribution was carried out on the early cretaceous mudstones of the tengger formation in the erlian basin northern china to define source rock geochemical characteristics depositional environment and tectonic setting of small faulted basin the biomarkers of mudstone extracts are characterized by short to middle chain n alkanes high cpi values 1 12 a wide range of pr ph 0 4 1 94 relatively high concentrations of c 29 sterane and the presence of relatively low tricyclic terpanes and low gammacerane index values 0 01 0 25 which is consistent with a relatively oxic to anoxic depositional environment of fresh to brackish water conditions with a major contribution of terrigenous organic matter input and a low contribution of aquatic algal bacterial organic matter the oxic to anoxic depositional environment of small fault basins and a fresh and brackish water conditions are also confirmed by reduced sulphur organic carbon ratio and element distribution in these small fault basins the cross plots of 13 c carb and toc show that productivity has an obvious control on source rock development the differences in tectonic settings cause variations in productivity redox conditions and terrigenous organic matter input which account for the distinctly different geochemical characteristics and depositional environment of source rocks in small fault basins

molecular and petrographic indicators of redox conditions and bacterial communities after the f f mass extinction kowala holy cross mountains poland abstract pyrite framboid diameter analysis and organic geochemistry of the triangularis crepida boundary section at kowala holy cross mountains poland imply suboxic to oxic and sporadically euxinic bottom waters during the lower famennian in addition morphological web like structures typical for microbial mats as well as the recognition of 2 methylhopanes and monomethyl alkane cyanobacteria biomarkers is evidenced of microbial activity after the global frasnian famennian f f extinction event the presence of cyanobacterial mats also suggests suboxic to oxic environments and at the same time photic bottom water conditions however isorenieratane and its derivatives were detected in almost all samples the presence of this well known biomarker of green sulfur bacteria implies that euxinic conditions were present in the upper part of the water column at least intermittently or that temporal euxinia occurred in the water column presence of euxinic conditions is confirmed by the occurrence of small sized pyrite framboids which were particularly dominant in the lower part of the section the shift towards low 13 c values in both micritic limestones and in sedimentary organic matter seen at the beginning of the period of diminished photic zone might reflect an influx of newly respired co 2 to surface waters caused by enhanced respiration at depth after the f f transition in the checiny zbrza basin

the expression of the hangenberg event latest devonian in a relatively shallow marine succession pomeranian basin poland the results of a multi proxy investigation the uppermost famennian lowermost tournaisian interval has been analysed in detail using biostratigraphy sedimentology magnetic susceptibility and geochemistry in a reference section of the relatively shallow carbonate ramp environment within the pomeranian basin high resolution biostratigraphic study based on miospores allows recognition of the standard western european lepidophyta nitidus ln and verrucosus incohatus vi zones as well as the convolutispora major zone a local pomeranian equivalent of the european standard hibernicus distinctus hd zone the sedimentary succession and specific phenomena recognized close to the devonian carboniferous boundary such as fluctuations in water column euxinia wildfire evidence relative sea level changes and perturbations of the carbon cycle reflected by positive carbon excursions display a pattern partly similar to that observed in many areas in europe during the hangenberg event although the hangenberg black shale horizon is not developed here these important microscale environmental perturbations were observed not only within the famennian ln miospore zone but in a wide interval between the ln and the lowermost local convolutispora major miospore zones lower part of hd standard miospore zone it is still uncertain whether the recognized event s were connected solely with the hangenberg event which was possibly complex and multi phased as is sometimes suggested or whether they represent a succession of regionally limited post hangenberg events this question needs to be further investigated on broader stratigraphic and geographical scales

biomarker distributions in crude oils and source rocks from different sedimentary environments abstract the saturated and aromatic hydrocarbons from a significant number of oils and source rocks derived from terrestrial and marine organic matter have been analysed by gc and gc ms results show that certain classes of biomarkers including bicyclic sesquiterpanes tricyclic terpanes pregnanes methylsteranes rearranged steranes hopane sulfides benzohopanes long chain alkylbenzenes and pentacyclic triterpanes can be used to distinguish differences in source input and or depositional environments variations in the distributions of the naphthalenes phenanthrenes fluorenes dibenzofurans dibenzothiophenes naphthobenzothiophenes and triaromatic steroid hydrocarbons may also reflect disparities in source input or sedimentary environments

geochemistry of oils from the northern timan pechora basin russia abstract a geochemical study of 36 oils from the northern timan pechora basin indicates four oil types two types of sulfur rich oils range 1 4 2 5 sulfur can be identified on the basis of both gross and molecular properties these oils are found primarily in the toravey south toravey and roman trebs fields they are also present in the offshore prirazlom field thereby extending the geographic range of sulfur rich oils into the pechora sea another oil type exhibits a distinctive odd predominance of n alkanes in the range n c 11 through n c 19 and a diminished abundance of n alkanes greater than c 19 these oils which occur primarily in the a titov and labogan fields show striking similarities to ordovician sourced oils from other paleozoic basins throughout the world their biomarker and isotopic compositions for example bear a strong resemblance to oils generated from the ordovician viola limestone of the anadarko basin the fourth oil type occurs in the northwestern portion of the basin in the khylchuyu field some mixing between the various types is evident light oils and condensates of the peschano ozyor shtokman rusanov and vasilkovo fields cannot be readily assigned to any of these four types the upper devonian domanik formation is generally thought to be the major oil source in the timan pechora basin however geochemical characteristics of timan pechora oils analyzed do not closely resemble those of other upper devonian source oils such as those generated from the duvernay formation of western canada these differences might reflect variations in the organic matter preserved in the two basins during the late devonian or may indicate that the upper devonian is not an important hydrocarbon source in the northern timan pechora region the results suggest that the timan pechora oils analyzed are generated from paleozoic carbonate or calcareous shale source rocks at least one of which appears to be of ordovician age

geological constraints on cave development in the plateau gorge karst of south china wulong chongqing abstract the houping tiankeng cluster is a part of the south china karst unesco world natural heritage site within the distinctive wulong plateau gorge karst 200 km of cave passages have been documented to date this paper focuses on detailed tectonic and morphological research on the luo shui kong cave enriched with u series dating of speleothems and complemented by morphometric analysis of the san wang dong and er wang dong caves all of these caves exhibit three regional levels of cave development 1 1040 1020 m a s l 2 900 840 m a s l and 3 740 660 m a s l the houping tiankeng area is a carbonate rock sequence several hundred meters thick overlain by the less soluble lower ordovician strata limiting recharge points to faults exposing underlying easily soluble formations this leads to the domination of concentrated high volume inflow and thus results in caves of large volume in the plateau gorge karst shafts connecting the surface with cave passages located underneath formed along faults changing the hydrogeological pattern through karst water capture and remodeling of existing conduits albeit mainly by increasing their overall dimensions rather than by deepening them the most favorable structures for cave level development are two sets of joints conjugated with gently inclined bedding since these joints are characterized by a small vertical extent downward development is limited hence most of the passages are wide but not deep canyons and typical of a water table cave pattern places where the fault plane is eroded from the surface and where at the same time an underneath cave chamber ceiling expands upwards are particularly predisposed to the formation of a tiankeng

facies patterns and depositional environments of palaeozoic cephalopod limestones abstract in the eastern anti atlas morocco a platform and basin topography was established during the late devonian probably as a result of early variscan tensional tectonics cephalopod limestones were deposited on shallow pelagic platforms platform slopes and shallow slowly subsiding basins on the platform a transition from land areas into nearshore quartzose brachiopod coquinas crinoidal limestones condensed cephalopod limestones and finally into nodular limestones is observed the latter often become disintegrated into incipient debris flows which pass into nodular limestone marl alternations of a shallow basin deeper basins with shale sedimentation lack cephalopod limestones similar facies types also occur in the late devonian of the montagne noire france rheinisches schiefergebirge west germany moravian karst czechoslovakia holy cross mountains poland and in the early carboniferous of the cantabrian mountains spain due to strong late variscan compressional tectonics and limited outcrops detailed facies patterns could not be mapped in these regions but the same facies types as in the eastern anti atlas suggest similar coast platform slope and shallow basin topographies during cephalopod limestone deposition water depth on the platforms was in the order of several tens to about one hundred metres as is inferred from repeated subaerial exposures and distinctive depositional and faunal floral features water depth in the adjacent shallow basins might have reached several hundreds of metres cephalopod limestones represent a typical stage in the evolution of geosynclines characterized by extremely low sedimentation rates 1 5 m m y 1 this stage is preceded by deposition of thick neritic clastics and or carbonates and is succeeded by deposition of deep water clastics or flysch

organic petrology and organic geochemistry of devonian black shales in southwestern ontario canada abstract the hydrocarbon source rock potential of the devonian marcellus and kettle point black shales in southern ontario has been assessed using rock eval pyrolysis gas chromatography gas chromatography mass spectrometry and incident light microscopy both formations contain sufficient hydrogen rich organic matter type ii to be considered possible source rocks the kerogen is predominantly marine in origin this organic matter was deposited in a clastic algal dominated environment and mainly consists of unstructured bituminite and unicellular alginite the organic microfacies indicate shelf paleodepositional settings with a transition to an open basinal region the optical reflectance fluorescence and geochemical rock eval tmax extract yields distributions of steranes and terpanes maturity data indicate that the organic matter in the kettle point formation is immature whereas in the marcellus formation it has reached the early stages of hydrocarbon generation and expulsion some devonian oils occurring in this area have characteristics similar to the marcellus extracts suggesting that more mature equivalent units from the appalchian basin could be their source

biomarkers as environmental indicators in a carbonate complex example from the middle to upper devonian holy cross mountains poland abstract autochthonous biomarker distributions were studied in an array of different subfacies of a devonian carbonate complex represented in platform reef and off platform shelf basinal systems it revealed that biomarkers are sensitive indicators of depositional environments and may serve to refine palaeoenvironmental interpretations of carbonate complexes based on classical sedimentological facies analyses the contrasting biomarker composition of the carbonate platform and reef complex versus shelf basin deposits is here interpreted as the effect of both more diverse biotic sources of a primary organic matter in the former environments highly scattered results of sterane distribution and contrasting styles of decay and bacterial reworking of the primary biomass peritidal dolostones deposited under anoxic to suboxic conditions and with scarce sedimentological evidence of elevated salinity reveal the highest potential of organic matter preservation among other platform reefal facies their biomarker composition includes several compounds indicating hypersaline conditions and anoxia whereas others in particular gammacerane indicate that the water column was stratified during sedimentation this observation constrains environmental interpretation of these deposits pointing to shallow subtidal lagoons with elevated salinity and low oxygen near bottom waters most probably originating from a salinity controlled stratification of the water column biomarkers diagnostic of green sulphur bacteria were found in both peritidal lagoonal dolostones and shelf basinal facies this indicates the existence of photic zone anoxia in the latter environment thus suggesting a shallow position of the redoxcline the frasnian famennian mass extinction event s apparently had no impact on the biomarker distribution in the shelf basinal system continuous across the stage boundary

preservation and diagenesis of hopanoids in recent lacustrine sediments of priest pot england abstract absolute concentrations of various bio and geohopanoids have been determined in a 24 cm long core from anoxic recent sediments of priest pot a small highly productive lake in the english lake district samples were soxtherm extracted derivatised by methods targeted at specific hopanoid groups and quantified by gc ms periodic acid sodium borohydride treatment was used to cleave the side chains of highly functionalised hopanoids producing products more amenable to our detection methods biohopanoids are extremely abundant totalling up to 3000 g g dry sediment particularly those with composite or highly penta and hexa functionalised side chains suggesting that these are important precursors to sedimentary hopanoids in priest pot downcore biohopanoid abundance profiles show a general diagenetic decline with a marked dip at 5 8 cm which we interpret as a change in bacterial input since this is most marked in the composite hopanoids rather than bacteriohopanetetrol we suggest that these two hopanoid groups have at least partly different sources and may thus have potential as environmental markers the geohopanoids are also abundant totalling up to 1700 g g dry sediment being dominated by the and bishomohopanoic acids and bishomohopanol and hop 17 21 ene downcore plots show no apparent conversion of free bio to geohopanoids with depth which suggests that incorporation into kerogen may be commencing at an early diagenetic stage in the sediments

tricyclic terpanes in precambrian bituminous sandstone from the eastern yanshan region north china a bituminous sandstone at the base of the xiamaling formation precambrian is a fossil oil pool which was thermally altered into reservoir bitumen 760 ma ago this reservoir bitumen was extracted fractionated and analyzed for biomarkers a novel series of extended tricyclic terpanes c18 c23 with a 13 n alkyl side chain configuration was identified by co injection of two standards c18 c20 and gc ms analysis some bicyclic sesquiterpanes c18 norditerpanes regular extended tricyclic terpanes c18 c24 no c22 and alkylcyclohexanes were also detected the source of the organic matter its alteration in the sandstone reservoir and the origin of its novel tricyclic terpanes are all inferred to be microbial

organic geochemical evaluation of cretaceous shale samples from the orange basin south africa abstract organic geochemical evaluation of thirty two aptian to campanian shale samples from seven wells drilled on the shelf of the orange basin southwestern atlantic margin was carried out in order to determine their origin depositional environment thermal maturity and hydrocarbon potential the shale samples selected to represent highstand lowstand and transgressive systems tracts were analysed by rock eval pyrolysis for total organic c characteristics and by gas chromatography gc and gas chromatography mass spectrometry gc ms for n alkanes aliphatic isoprenoid hydrocarbons and biomarkers steranes hopanes and tricylic terpanes for most of the shale samples rock eval data hydrogen hi and oxygen index oi point to mainly type iii terrigenous organic matter only a few samples of turonian age reveal a higher proportion of marine organic matter being classified as type ii iii or type ii biomarker parameters suggest that the samples are deposited under suboxic to oxic environmental conditions rock eval data and biomarker maturity parameters assign for most of the samples a maturity level at the beginning of the oil window with some more mature samples of aptian albian and cenomanian age the hydrocarbon generation potential is low for most of the shelf shales as indicated by the s2 s3 ratio and hi values exceptions are some samples of turonian and aptian age

effects of source thermal maturity and biodegradation on the distribution and isomerization of homohopanes in petroleum abstract the distributions of c31 c35 17 21 h homohopanes in marine petroleums can be used to describe redox conditions in the source rock depositional environment for example high c35 homohopane indices c35 c31 c35 are typical of petroleums generated from source rocks deposited under anoxic marine conditions where the c35 backbone of the precursor bacteriohopanetetrol is preferentially preserved homohopane distributions have been used to distinguish petroleums from different organic facies of the same source rock homohopane distributions are altered by secondary processes for example the c35 homohopane index decreases with increasing api gravity and thermal maturity of related oils from the monterey formation offshore california similar decreases in the homohopane index are observed for expelled oils from monterey source rock during hydrous pyrolysis biodegradation can result in selective loss of high or low molecular weight homologs apparently depending on the bacterial population in the reservoir bacterial demethylation of homohopanes appears necessary to explain 25 norhopanes in at least one biodegraded oil hydrous pyrolysis studies of the phosphatic and siliceous members in the monterey formation show that identical heating conditions result in different homohopane c 22 epimer ratios furthermore a reversal in the trend of the epimer ratio at high experimental temperatures is observed for the phosphatic but not for the siliceous lithology this could be caused by the combined effects of isomerization and differential thermal destruction of epimers at high temperatures possibly mediated by rock mineralogy

palynofacies and source rock potential of jurassic sequences on the arruda sub basin lusitanian basin portugal abstract the study of the organic matter present in sedimentary rocks is fundamental for the characterization of the potential source rocks as well as to define the depositional paleoenvironments parameters of organic petrology and organic geochemistry and their variations along sedimentary successions are essential tools to achieve these goals two borehole successions freixial 1 and benfeito 1 from arruda sub basin lusitanian basin that comprise siliciclastic carbonate deposits of jurassic age have been studied in order to characterize the organic matter and its vertical variability as well as its hydrocarbon potential palynofacies and geochemical data indicate both marine including zooclasts and terrestrial organic matter where the phytoclasts predominated despite an important contribution of the amorphous organic matter aom different types of solid bitumen were observed most of the analyzed samples have total organic carbon content toc lower than 1 wt and hydrogen index hi values lower than 100 mghc g toc revealing types iii and iv kerogen however one set of samples exhibit toc values higher than 1 wt and higher hi values depicting a type ii kerogen the biomarker data showed a dominance of n alkanes with 15 30 carbon atoms having a unimodal distribution pristane phytane ratio varies between 0 04 and 1 84 indicating an alternation of oxic anoxic conditions along the sequences typical terpane distributions are characterized by the presence of tricyclic and tetracyclic terpanes as well as pentacyclic terpanes rare in carbonated samples from freixial 1 borehole the amount of 17 h 22 29 30 trisnorhopane tm usually exceeds the amount of 18 h 22 29 30 trinorneohopane ts the values of the ratio 22s 22s 22r epimers of c32 homohopanes revealed that most samples reached equilibrium values the 20s 20s 20r and isomerization ratios in c29 sterane calculated for the studied samples range between 0 19 0 61 and 0 20 0 70 respectively with several samples reaching the equilibrium values the vitrinite reflectance values are higher than 0 5 indicating that the organic matter reached the oil generation window according to the data obtained in this study the abadia montejunto cabacos and brenha formations can be considered potential source rocks of hydrocarbons gas and or oil in this section of the lusitanian basin