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

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

variations in the sterane carbon number distributions of marine source rock derived crude oils through geological time abstract the analysis of the sterane data of a large set of crude oils 414 derivedfrom marine carbonate 27 and siliciclastic source rocks 14 where influences of terrestrial or lacustrine derived organic matter can reasonably be excluded shows that there are increases in the relative content of c28 steranes and decreases in the relative content of c29 steranes through geological time there are no consistent variations in the relative content of c27 steranes through time with one major exception a proterozoic oil from oman palaeozolic and older crude oils are thus generally characterised by strong predominances of c29 steranes and low relative concentrations of c28 steranes significantly higher proportions of c28 steranes and lower proportions of c29 steranes occur in oils derived from jurassic and upper cretaceous source rocks these changes through time do not appear to reflect the chemical evolution of the sterols of one particular variety of marine organism the increase in c28 steranes may be related to the increased diversification of phytoplantonic assemblages in the jurassic and cretaceous possible sources of the c28 sterols necessary for the observed changes in crude oil steranes includes diatoms coccolithophores and dinoflagellates although the technique does not give an accurate means of determining the age of the source rock of a crude oil it is possible to distinguish younger crudes derived from the upper cretaceous and tertiary from palaeozoic and older crudes

oils and source rocks from pauls valley anadarko basin oklahoma u s a abstract thirty oils from the pauls valley area of the anadarko basin oklahoma have been analyzed for n alkane terpane and sterane distributions in an effort to classify genetically related oils ten rock samples from the area were also analyzed in an attempt to relate oil types to their possible source rocks the pauls valley area located near the southeast corner of the anadarko basin has producing formations ranging in age from middle ordovician to late pennsylvanian trapping mechanisms responsible for the accumulation of hydrocarbons vary from purely structural traps to fractured reservoirs to up dip truncations of reservoirs and up dip pinchouts of sandstones results show that 85 of oils in the area probably have a common source the woodford shale a group of oils reservoired in the viola group exhibit distinct geochemical characteristics and are thought to have a different source the differences between the oils from these two sources include enhanced c 24 tetracyclic terpane concentrations relative to c 26 tricyclic terpanes diminished c 28 30 tricyclic terpanes relative to t s and t m diminished c 30 steranes relative to their c 29 counterparts predominance of c 35 over c 34 extended hopanes and an even odd predominance of the normal alkane distribution extracts from the viola group generally exhibit the same qualities as the associated oils and the limestone is proposed as their probable source rock the predominance of c 29 steranes for oil samples which appear to have a marine source inferred by their n alkane distribution the presence of c 30 steranes and high levels of tricyclic terpanes suggests that caution be used in the interpretation of terrigenous sources based on the high abundance of c 29 steranes the deese group the springer formation the sylvan shale and the arbuckle group are not likely sources for the oils analyzed from the pauls valley area differences in api gravity and color previously used to classify oils in this region are not source related but are related to maturation and migration effects

characterization of rough walled fractures in crystalline rocks the full characterization of the rough surfaces of fractures and their resulting apertures is an important step in the drive toward an improved understanding of the factors which control fluid flow through rocks this is crucial in igneous and metamorphic rocks since fractures in these rocks may form the only significant pathways for fluid migration here we describe a three pronged approach for the full characterization of rough fracture surfaces in a selection of crystalline rocks using a suite of software developed in house firstly profiling is carried out using an optical method which converts images of epoxy fracture surfaces covered with dyed water into topographies using the lambert beer law many hardware and software optiprof developments give this method the upper hand over previous attempts at spectrophotometric analysis it is not possible to profile every fracture surface therefore numerical modelling of fluid flow is carried out using synthetic fractures with rough fracture surfaces that are representative of the natural rock fractures parafrac allows the analysis and parametrization of fracture surfaces and apertures synfrac enables the numerical synthesis of fracture surfaces and apertures with prescribed basic parameters both procedures take full account of the complex matching properties of the fracture surfaces as a function of wavelength as well as anisotropy within the properties defining the fracture surfaces and their resulting aperture they have been rigorously tested on a large suite of synthetic fractures as well as real rock fractures these tests have allowed relationships between the standard deviation of surface asperity heights the fractal dimension and the matching parameters to be related to the resulting aperture of the fractures

biochemical evolutionary significance of ordovician oils and their sources abstract geochemical data from several ordovician oils and kerogens from distinct basins in canada united states estonia and australia show some unique compositional characteristics the oils analyzed by gas chromatography and gas chromatography mass spectrometry are characterized by an odd dominance in the c9 c19 molecular weight range of normal paraffins and an odd dominated homologous series of cyclohexyl substituted normal paraffins the oils contain an unusually small amount of c20 components and pristane and phytane are conspicuous by their virtual absence the compositions of the oils and kerogens correlate closely and display characteristics that have not been observed in younger sediments the predominant organism found in the source kerogens for these unique oils is gloeocapsamorpha prisca a primitive prokaryotic organism data from the analysis of gloeocapsamorpha rich kerogens and the association of this organism with ordovician source rocks indicate a genetic relationship exists between the organism and the unusual oil chemistry the chemistry of the oils and kerogens suggests that gloeocapsamorpha was either non photosynthetic or that it fixed light using a chlorophyll that did not contain a phytyl side chain e g a bacteriochlorophyll the widespread occurrence of oils and kerogens possessing such a uniform composition appears unique to the ordovician certainly to the early paleozoic this suggests that paleocological conditions of ordovician anoxic environments were very similar and g prisca was particularly well adapted to these conditions

middle ordovician organic matter assemblages and their effect on ordovician derived oils two distinct middle ordovician oil prone organic matter assemblages occur in thermally immature to marginally mature petroleum source rocks from iowa the substantially more oil prone assemblage a generates the unique ordovician oil fingerprint which has been associated with the organic walled microfossil gloeocapsamorpha prisca the second assemblage b generates a more ordinary signature the two assemblages which are mixed or interbedded in many ordovician sediments of north america explain the variations in oils derived from ordovician source rocks these mixtures also aid in interpretation of the chemistry of g prisca core samples examined are from three wells in iowa penetrating the primarily carbonate sequence from the guttenberg member of the decorah formation down to the st peter sandstone microscopy rock eval pyrolysis and capillary gas chromatography on source rock bitumen extracts and nearby oils were used to evaluate the two assemblages solvent extracts from rocks containing predominantly assemblage a have the diagnostic ordovician gas chromatographic signatures with an odd preference in c11 c19 normal alkanes low amounts of heavier normal alkanes and virtual absence of isoprenoids including pristane and phytane although assemblage a occurs only in very thin beds it is potentially so oil generative that thicknesses in inches may be significant extracts from r cks containing predominantly assemblage b show reduced odd preference a full profile of normal alkanes and conspicuous occurrence of isoprenoids including pristane and phytane these samples from iowa are representative of middle ordovician source rocks found in most paleozoic basins of north america as well as baltic europe and australia therefore the conclusions drawn from these middle ordovician rock samples from iowa provide a basis to explain variations in ordovician derived oils found in many other areas

the origins of petroleum in the northern gulf of mexico abstract the distribution and chemistry of oils in the northern gulf of mexico and the adjacent onshore can be explained by multiple sources fades variations maturation and post generation alteration genetic families include jurassic smackover flexure trend upper cretaceous and paleogene oils smackover oils have high sulfur contents pristane phytane ratios c 35 c 34 hopane ratios 1 0 and c 30 c 29 hopane ratios usuall 1 0 flexure trend oils are similar and contain abundant extended hopanes high sulfur contents and v ni v 0 5 these oils are inferred to be sourced in upper jurassic lower cretaceous strata upper cretaceous oils contain a distinctive suite of tricyclic and nonhopanoid triterpanes oleanane is low or absent paleogene oils can be recognized by the presence of 18 h oleanane and a lack of extended hopanes these oils occur from south texas to southern and offshore louisiana two subfamilies can be recognized based on the relative abundance of triterpanes and steranes these oils have a presumed paleogene source mixing of oil types is quite prevalent at the geographic boundaries of oil types the initial control on the distribution of oil and gas in the northern gulf of mexico is provided by the areal extent of source rocks secondary control is due to cenozoic deposition which provides the thermal stress to generate as well as destroy oil salt tectonics provide conduits for migrating fluids to escape the zone of thermal destruction mesozoic source strata again become important in the deep gulf of mexico where cenozoic sediments thin

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

oil families and their potential sources in the northeastern timan pechora basin russia oil and rock samples collected throughout the northeastern timan pechora basin identify key oil families and correlate these oil families to stratigraphic units that sourced them based on distinctive molecular characteristics three distinctive hydrocarbon systems have been identified within the northeastern timan pechora basin hydro carbons both oil and gas are found in clastic and carbonate reservoirs from the lower silurian to the triassic three major oil families have been identified based on physical properties gas chromatography liquid chromatography and gas chromatography mass spectrometry family a oils are found in permian silurian reservoirs within the sorokin swell and upper devonian reservoirs within the eastern and western edges of the khoreyver depression this oil family is sourced from an upper devonian bitumen laminated carbonate mudstone informally known as the domanik facies family b oils are found only in upper devonian reservoirs within the central khoreyver depression this oil family is most likely sourced from upper devonian hypersaline marine mudstones with significant bacterial input many of the family b oils were generated at temperatures less than that for peak oil generation family c oils are found in carboniferous lower devonian reservoirs within the northern sorokin swell this family is sourced from marine mudstones that have gloecapsamorpha prisca as well as other marine algae present organic rich lower devonian and silurian shales contain similar molecular characteristics and are potential sources for the family c oils

tectonic and geodynamic setting of oil and gas basins of the soviet union within the territory of the soviet union and its offshore economic zone are about 70 sedimentary basins containing oil and gas the basins include almost all basin types described in present day plate tectonic classifications namely 1 intracontinental and pericontinental rifts suprarift syneclises and zones of pericratonic downwarps 2 ancient passive margins of continents with adjacent overthrust fold system 3 modern passive margins of continents 4 zones of convergence of lithospheric plates i e zones of subduction of oceanic plates below continental plates and 5 zones of collision of continental lithospheric plates basins of the first type include the pripyat dnieper donets aulacogen the viluy aulacogen of siberia the huge west siberian supra aulacogen basin the analogous yenisei khatanga basin and others the second type includes the volga urals basin with the ural foredeep azov kuban basin and terek caspian basin with the greater caucasus foredeeps and others the difference between these two types is rather arbitrary because the passive margins of continents also undergo the rift stage of development though their main stage of oil and gas accumulation corresponds to the post rift stage the third type is represented by the poorly studied prospective basins of the arctic margin of the soviet union the fourth includes numerous but relatively small basins of the far eastern and northe stern soviet union of which the east sakhalin west kamchatka and anadyr basins have proved to contain oil and gas rifting also played a role in the formation of the back arc group of these basins basins in central asia fergana south tadjik and the transcaucasia region south caspian belong to the fifth basin type the central asian basins lie within the area of secondary epiplatform orogenesis whereas the transcaucasian basins are with the area of primary epigeosynclinal orogenesis so far the only type of basin not identified within the territory of the soviet union is the pull apart basin the location and distribution of oil and gas deposits in the section of a basin prevailing types of traps and scale of potential resources are all features influenced by the geodynami type of the basin

origin and occurrence of 25 norhopanes a statistical study abstract the alkane fraction of more than 200 rocks biodegraded oils and non biodegraded oils have been analysed by means of computerized gc ms in order to investigate the effect of natural biodegradation on the occurrence of demethylated hopanes i e 17 25 norhopanes the results obtained indicate that 25 norhopanes are preexisting biomarkers the concentration of which is enhanced by selective biodegradation of more readily degradable homologs i e regular hopanes rather than by demethylation of hopanes in reservoirs however the use of 25 norhopane enrichment as a palaebiodegradation indicator in apparently non biodegraded oils is still valuable providing the initial background content in the corresponding source rocks is known furthermore 25 norhopanes appear to be diagnostic of specific environmental conditions marine and lacustrine source rocks dysoxic and not very hypersaline lastly one other novel bacterially resistant rearranged hopanoic compound namely a c29 neohopane is applicable for both biodegradation and maturation evaluation

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

geochemistry of selected oils and rocks from the central portion of the west siberian basin russia six analyzed oils produced from middle jurassic to upper cretaceous strata in the middle ob region of the west siberian basin show biomarker and stable carbon isotope compositions indicating an origin from the upper jurassic bazhenov formation the chemical compositions of these oils are representative of more than 85 of the reserves in west siberia kontorovich et al 1975 bazhenov sourced oil in cenomanian strata in the van egan field underwent biodegradation in the reservoir resulting in a low api gravity an altered homohopane distribution and the appearance of 25 norhopanes without alteration of the steranes high api gravity oil from the salym field has surpassed the peak of the oil window consistent with abnormally high temperatures and pressures in the bazhenov source rock from which it is produced the remaining oils are very similar including samples from valanginian and bathonian callovian intervals in a sequence of stacked reservoirs in the fedorov field bazhenov rock samples from the study area contain abundant oil prone marine organic matter preserved under anoxic conditions organic matter in a bazhenov core from the pokachev 58 well was compared with the oils because it is thermally mature and shows total organic carbon toc 13 8 wt and hydrogen index values hi 489 mg hc g toc representative of the average for the formation 10 7 wt for 840 samples 420 mg hc g toc for 75 samples other rocks in the middle ob region are far less likely to have generated these oils than the bazhenov formation no prospective source rocks older than middle jurassic were available geochemical analyses indicate a lack of thermally mature hauterivian or younger source rocks in the study area core samples from the lower cretaceous frolov formation either are thermally immature hauterivian or show little oil generative potential berriasian valanginian the upper jurassic vasyugan formation shows lower oil generative potential than the bazhenov formation the average toc for vasyugan rocks is 3 20 wt 240 samples average atomic h c ratios for vasyugan and bazhenov kerogens are 0 90 10 samples and 1 13 25 samples respectively the vasyugan formation cannot be excluded as a source rock because insufficient sample was available for biomarker analysis core from the lower to middle jurassic tyumen formation in the yemyegov 15 well was compared with the oils because it is thermally mature and shows toc and hi values 2 78 wt and 137 mg hc g toc respectively indicating slightly more favorable oil generative characteristics than the average for the formation 2 75 wt for 720 samples 95 mg hc g toc for 25 samples the core contains terrigenous gas prone organic matter that shows no relationship with the analyzed oils

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

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

organic geochemical study and genetic correlation of natural gas oil and menilite source rocks in the area between san and stryi rivers polish and ukrainian carpathians abstract we studied the source rocks and petroleum accumulations in the carpathian mountains of the polish ukrainian border area between the san and stryi rivers a total of 108 oligocene menilite formation rock samples 12 oil and 15 gas samples accumulated in the oligocene reservoirs and one oil and gas sample from an upper cretaceous reservoir were analysed the aim of this study was to evaluate the petroleum potential of the menilite formation in this area and to evaluate potential genetic correlations between source rock and petroleum the menilite formation represents a prolific source rock with toc content ranging from 2 to 7 wt locally exceeding 20 wt algal type ii and mixed type ii iii kerogens dominate but sometimes type iii kerogen and rarely type i kerogen occur thermal maturity of the oligocene menilite formation increases from outer to inner tectonic units from the immature in the boryslav pokuttya and skole units to the overmature in the southern parts of silesian and dukla units as a consequence petroleum potential decreases in the same order geochemical analyses reveal that oil and gas generation and migration processes within the carpathian flysch succession are complicated all analysed oils were generated from the menilite formation during early and peak stages of the oil window associated gas is of low temperature thermogenic origin sometimes containing an admixture of microbial gas high temperature thermogenic gas occurs only in the polish part of the silesian unit

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

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

oil generation in the michigan basin a biological marker and carbon isotope approach abstract palaeozoic strata in the michigan basin produced crude oils which despite their rather small volume and economic value are interesting because of the considerable age of the basin and because of the opportunity to study generation and migration of oils within a relatively simple but ancient geological setting based on n alkane profiles biological marker distributions and carbon isotope ratios the oils belong to three main families of different genetic origin and a few less important mixed types silurian oils from salina and niagara limestones have broad n alkane distributions and abundant isoprenoid hydrocarbons a strong phytane over pristane predominance and the lack of diasteranes indicate a carbonate source for these oils chemical maturity parameters show that they are more mature than the oils from the other main families from which they are also clearly distinguished by carbon isotope ratios of hydrocarbon fractions and single n alkanes oils found in the calcareous ordovician trenton formation contain n alkane cyclohexylalkane and alkyl phenanthrene distributions typical of immature oils many oils from the devonian dundee reservoirs are very similar in overall composition to the trenton oils devonian traverse oils are considered to be mainly from a devonian source with some contribution of ordovician type oil and are of intermediate maturity based on calculations using kinetic parameters of biological marker reactions considerably deeper subsidence of the devonian source rock in the past is implied

aromatic hydrocarbon composition of the permian kupferschiefer in the lower rhine basin nw germany the aromatic hydrocarbon composition of 25 samples of permian kupferschiefer from the lower rhine basin of nw germany has been investigated using gc gc ms and direct probe ms analysis two narrow sampled profiles were investigated with respect to compositional changes during kupferschiefer sedimentation and samples from 13 different wells covering a depth range from 350 to 1000 m were included in order to study temperature sensitive variations in the kupferschiefer trimethyl substituted aryl isoprenoids in the range from c11 to c21 occur these compounds presumably are degradation products of isorenieratane which is also present in the extracts within the profile the amount of a preferentially occuring c29 chroman increases from the bottom to the top of the kupferscheifer by a factor of about 2 5 the chroman distribution observed in the kupferschiefer points towards euhaline to mesohaline seawater during sedimentation moreover in the investigated profiles a terrestrial source input mainly in the bottom most part of the shale is reflected by the occurrence of a monoaromatic c24 chrysene derivative presumably derived from ring a degradation of pentacyclic triterpenes

modification of the petroleum system concept origins of alkanes and isoprenoids in crude oils kerogen the source material for petroleum can have a long history of alteration and diagenesis before crude oil forms a common assumption is that the bulk composition of the expressed oil reflects so much of these progressive alterations that most of the primary biological information of the original fixed carbon has been lost exceptions are trace constituents the biomarkers that comprise only a fraction of the organic material in most pristine crude oils analysis of the alkane acyclic isoprenoid fraction of a large number of crude oils and rock extracts from the timan pechora basin russia suggest that this fraction the main constituent of most crude oils is a direct product of liquefaction of biological debris that was preserved essentially unaltered to the point of oil generation therefore the primary biological provenance of this fraction is preserved in the oil fraction a set of gas chromatographic analyses of 242 crude oils as well as 83 solvent extracts from upper to middle paleozoic putative source rocks from the timan pechora basin russia were analyzed by a multivariate data analytical procedure new to organic geochemistry the distributions of n alkanes and acyclic isoprenoids 24 in all in the 325 samples could be reproduced by linear combinations of six end member compositions attributed to distinct biological inputs four of the six are assigned to primary producers waxes from higher plants cyanobacteria microalgae and the microorganism gloeocapsomorpha prisca these end members account for most of the n alkanes and acyclic isoprenoids in our samples the other two represent the products of secondary bacterial alteration of primary organics during sedimentation and low level bacterial alteration in the reservoir biodegradation each end member is composed of a spectrum of analytes whose abundances are related to one another by fixed ratios we surmise that each primary end member represents the breakdown of a resistant biopolymer that forms cell walls and partitions of a given biological group the n alkanes and acyclic isoprenoids in crude oils represent the weighted signatures of their various ancestors i e their primary organic inputs if the precursors of most oils are the products of a small set of chemically simple biopolymers then many of our assumptions concerning the importance of total organic carbon and the nature of the oil window must be reexamined

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

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

cavalli seamount northland plateau sw pacific ocean a miocene metamorphic core complex cavalli seamount 34 06 s 174 10 e is an irregular shaped flat topped seamount on the northland plateau sw pacific ocean in contrast to miocene lavas recovered from other seamounts in the area the rocks dredged from cavalli seamount consist of biotite schist with minor calc silicate bands mineralogy whole rock chemistry u pb dating of detrital zircons and sr and nd isotopic composition collectively indicate a siliciclastic carbonate protolith of latest cretaceous to paleogene stratigraphic age metamorphic index minerals are sillimanite andesine garnet ilmenite and k feldspar and indicate peak p t conditions of c 650 c and c 0 4 gpa u pb ar ar and fission track dating of minerals and micropalaeontological dating of associated limestones indicate rapid cooling in the interval 23 21 ma the schist contains chloritized and hematized slickenslides parallel to a penetrative lineation s c planes and conjugate microfractures and has limestone geopetal infillings parallel to foliation these features are consistent with the interpretation of cavalli seamount as part of the lower plate of an early miocene metamorphic core complex although other explanations are possible the core complex interpretation fits with regional early miocene events including crustal thickening as a result of allochthon emplacement in northern new zealand crustal thinning associated with rapid extension in the south fiji basin pacific trench rollback and abundant early miocene igneous activity

detecting the source of heinrich layers an organic geochemical study 1 there are controversies regarding the origin of heinrich layer 3 h3 the massive ice rafting and meltwater event in the north atlantic during the last glacial cycle spanning a time window between 29 and 30 kyr b p some argue in favor of a laurentide ice sheet source similar to other heinrich layers while a contending view argues for the european ice sheet source existing geochemical proxies such as 40ar 39ar 206pb 204pb or nd etc could not be used to distinguish among various sources of ice rafted debris in h3 because of their low abundances suggesting a background glacial sediment signal in order to circumvent this problem a biomarker based approach is used to characterize the provenance of h layers 2 3 and 4 and other non heinrich layers the presence of hopanes and steranes and their aromatic counterparts in the h layers is incompatible with recent sediments and is attributed to the transportation of organic matter because of the glacial erosion of source rocks the most diagnostic and useful signatures of this ancient organic matter in the h layers are the dominance of c34 hopanoids over c33 and the occurrence of isorenieratane along with palaerenieratane biomarkers signatures in h layers 2 and 3 of the labrador sea suggest no difference in their source hydrocarbon distributions suggest that these sediments were derived from the middle to late ordovician and silurian source rocks of the hudson bay of eastern canada biomarker data of the h layer 4 from the northwest atlantic reveal that the sediments of this layer have a similar source to the h layers in the labrador sea

biomarkers and carbon isotopes of oils in the jurassic smackover trend of the gulf coast states u s a abstract the geochemistry of 25 oils from 23 fields in alabama and the mississippi and louisiana arkansas jurassic salt basins was evaluated results show that the oils were generated by a carbonate source rock which was deposited under highly anoxic conditions and which contains mainly marine derived organic matter the mississippi and louisiana arkansas oils are geochemically similar indicating similar depositional environments for the source although the alabama oils were also derived from a carbonate source rock they are dissimilar to the mississippi and louisiana arkansas oils terpane biomarkers suggest that in addition to marine derived organic matter the source for the alabama oils had an organic input from a more near shore paralic environment i e with a component of terrestrially derived kerogen within each area the oils are similar therefore the norphlet and upper smackover oils in alabama share a common source and the upper smackover cotton valley and some of the lower tuscaloosa oils where production is from faulted structures in mississippi also share a common source maturities of the oils in the three areas vary from low in the updip mississippi salt basin high in the louisiana arkansas salt basin to very high in portions of alabama based on the maturity of oils in mississippi oil generation and migration commenced during the cretaceous when the source was at modest levels of thermal maturity oils migrated relatively short distances into nearby reservoir rocks some oils reached high maturities in the reservoirs resulting in abundant late forming bitumen and pyrobitumen deposition in pore spaces