depositional environment and hydrocarbon source potential of the lower miocene oil shale deposit in the aleksinac basin serbia abstract the most prolific oil shale deposit in serbia is located in the aleksinac basin and is assigned to the lower miocene depositional environments and hydrocarbon potential were assessed for the aleksinac oil shale and coal layers through bulk geochemical organic petrographical biomarker and carbon isotope data from core samples from a single well maturity parameters vitrinite reflectance tmax biomarker isomerisation ratios prove that the organic matter om is immature a lower lacustrine oil shale sequence is comprised of alternating sandstone and clay rich rocks and some thin coal beds indicating strong variations in depositional environment this stratum is covered with thick sandstone 50 m terminated by the main 4 m thick coal seam that was deposited in a low lying mire as evidenced by high total sulfur and mineral matrix contents the plant input was dominated by angiosperms a relative rise in water level led to the drowning of the swamp and to the deposition of a 60 m thick upper oil shale in a lacustrine environment the om of the oil shale is dominated by kerogen type i lamalginite biomarker data suggest a stratified water column that likely formed due to differences in salinity the stratified water column led to a strictly anoxic environment and photic zone euxinia in a mesosalinar hydrologically closed lake which enabled the accumulation of uncommonly high amounts of organic material average toc 18 0 wt with excellent preservation average hi 743 mg hc g toc

the effect of clay minerals on diasterane sterane ratios to examine the effect of clay minerals on diasterane sterane ratios the mineral compositions of three sample sets of sedimentary rocks displaying a wide range of diasterane sterane ratios were analysed quantitatively diasterane sterane ratios do not to correlate with clay content but depend on the amount of clay relative to the amount of organic matter clay toc ratios this correlation may explain the high diasterane sterane ratios in crude oils and extracts derived from certain carbonate source rocks based on the concentrations of regular and rearranged steroids in the sample sets it is proposed that diasterenes are partly reduced to diasteranes and partly degraded during diagenesis in a ratio largely determined by the availability of clay minerals it is suggested that the hydrogen atoms required for reduction of the diasterenes originate from the water in the interlayers of clay minerals

negative estuarine circulation in the ria of pontevedra nw spain an along estuary negative circulation was measured in the ria of pontevedra nw spain on may 13 1998 this two layered circulation pattern with near bed water moving seaward and near surface water landward was generated by the existence of two different water masses at intermediate depths water in the inner part of the estuary was a mixture of estuarine water and eastern north atlantic central water enacw which had entered the estuary some days before due to an intense upwelling event water in the middle part of the estuary was a mixture of estuarine water and fresh water coming from the river discharge which had been higher during the days previous to may 13 this water mass distribution gave rise to the existence of denser water in the inner part of the estuary than in the middle one generating the observed negative circulation pattern

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

a newly discovered norisoprenoid 2 6 15 19 tetramethylicosane in cretaceous black shales a novel c24 acyclic isoprenoid 2 6 15 19 tetramethylicosane tme has been unambiguously identified using a synthesised standard in the saturated hydrocarbon fractions and in the kerogen pyrolysates of samples from a lower albian black shale from southeastern france in addition a novel c26 acyclic isoprenoid 10 ethyl 2 6 15 19 tetramethylicosane etme was tentatively identified these compounds appear to be structurally strongly related to the relatively well known c25 isoprenoid 2 6 10 15 19 pentamethylicosane pme and their co occurrence in these sediments and similar 13c contents indicates a common origin this suggests an alternative biosynthetic pathway for the biosynthesis of pme via the methylation of tme rather than the tail to tail coupling of farnesyl and geranyl these irregular isoprenoids are likely to have originated as parts of ether lipids in some unknown archaea but exactly which organisms biosynthesised these compounds remains uncertain

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

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

extended 8 14 secohopanes in some seep oils from pakistan abstract an alkane fraction isolated from pakistani oil seep samples using liquid chromatography on us y molecular sieves has been shown to contain six pseudohomologous series of tetracyclic compounds that have mass spectral characteristics of 8 14 secohopanes with carbon numbers extending to 35 this is the first report of extended 8 14 secohopanes in a crude oil although extended 8 14 secohopanes with up to 32 carbon atoms have previously been reported from a chinese coal of jurassic age the kovats indices of these extended 8 14 secohopanes are reported from measurements using capillary gas chromatography columns with nonpolar and polar stationary phases

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

triassic oils and potential mesozoic source rocks peace river arch area western canada basin abstract triassic oils and their potential mesozoic source rocks in the peace river arch region western canada basin have been examined using various analytical techniques triassic oils are divided into two groups 1 and 2 on the basis of biomarker composition triassic outcrop samples from the rocky mountain foothills are mature to overmature and contain type ii iii organic matter with toc s ranging from 0 1 to 15 0 wt and hi values up to 445 subsurface core samples from the triassic montney formation are mature to overmature with toc s rarely up to 2 8 wt and hi values up to 398 the triassic doig formation has good to excellent source potential and moderate to high maturity with toc values over 5 0 wt and hi values commonly in excess of 300 the jurassic nordegg member ranges from early mature to overmature with toc s as high as 23 5 wt and hi values greater than 600 where maturity is low oil source rock correlations are established based on biomarker signatures between the group 1 oils and the doig formation group 2 oil was sourced by the nordegg member

variations in abundances and distributions of isoprenoid chromans and long chain alkylbenzenes in sediments of the mulhouse basin a molecular sedimentary record of palaeosalinity abstract the abundances and distribution patterns of mono di and trimethylated 2 methyl 2 4 8 12 trimethyltridecyl chromans mttcs and long chain alkylbenzenes in extracts of marl 66 samples anhydrite 15 and halite 1 strata of the salt iv formation of the oligocene mulhouse basin are reported the distributions of the methylated mttcs indicate salinity changes of the upper part of a density stratified water column of the basin these variations are explained by a tectonically or climatically induced change in the supply of water of relative lower salinity to form a layer overlying the deeper water brine hence it is suggested that mesohaline 3 5 15 conditions in the surface waters were established as a result of periodic incursions of marine water and subsequent evaporation conversely during periods when the surface water was derived mainly from fresh water from the hinterland lower average salinity in the surface layer resulted the distributions of long chain alkylbenzenes also appear to record these changes

complex patterns of steroidal biomarkers in tertiary lacustrine sediments of the biyang basin china gas chromatography gc gas chromatography mass spectrometry gc ms and gas chromatography mass spectrometry mass spectrometry gc ms ms with co injected synthetic standards were used to analyse the biomarker patterns of some tertiary lacustrine clayey dolomites from the biyang basin china the lithology low pr ph ratio and high gammacerane content of these sediments indicated that high salinity prevailed during their deposition the distributions of steroidal hydrocarbons were particularly unusual and several pseudohomologous series including regular steranes c27 c29 4 methyl steranes c28 c30 including dinosteranes 3b ethyl steranes c29 c31 lanostanes c30 c32 and a variety of other 3b alkylated steranes were identified 3b n propylcholestane 3b n propylstigmastane and 4 4 dimethylcholestane were identified using authentic standards and this is the first time these compounds have been unambiguously characterised in sediments crown copyright 2001 published by elsevier science ltd all rights reserved

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

carbon isotopic composition of individual biomarkers in gilsonites utah abstract carbon isotopic compositions of saturated hydrocarbon aromatic hydrocarbon nso resin and asphaltene fractions of vein forming gilsonites cowboy bonanza independence wagonhound and harrison veins in the ne uinta basin utah are all similar and isotopically resemble mahogany zone shale extracts of the green river formation 13 c 29 to 31 individual molecular fossils in the gilsonites show a wider variability in compositions indicative of their paleoecological origins within the eocene uinta greater green river paleolake system carbon isotopic compositions of c28 and c29 steranes 13 c 25 to 32 pristance and phytane 33 to 34 and perhydro carotene carotane 13 c 33 2 suggest that organisms producing these compounds grew near the lake surface the c33 carotenoid lexane is isotopically identical to the c40 carotenoid carotane supporting a common c40 carotenoid precursor two groups of hopanes can be differentiated in the gilsonites based on carbon isotopic compositions c29 c31 and c32 hopanes and moretanes 40 9 to 44 3 consistent with a source from midwater bacteria and c30 hopanes and moretanes 51 0 and 60 5 for which the strong 13c depletion suggests at least partial derivation from methylotrophs the isotopic signatures of these molecular fossils suggest the source beds of the gilsonites were deposited in a stratified paleolake system with a depositional environment similar to that which formed the mahogany zone shales of the piceance creek basin algal biomarkers in the gilsonites are isotopically uniform throughout the area of the gilsonite vein occurrence 1500 km3 and resemble those in the mahogany zone shale in the piceance creek basin over 50 km to the east this remarkable lateral uniformity suggests that very similar photic zone water conditions existed across the entire uinta piceance creek paleolake system at the time of deposition of the gilsonite source bed mahogany zone shale sterane isotopic compositions are effective for the genetic correlation of the solid bitumens immature oils in contrast the carbon isotopic compositions of the bacterial biomarkers in the gilsonites vary significantly suggesting that conditions in deeper waters of the paleolake system were more variable carbon isotopic signatures of individual hopane biomarkers in the green river formation appear to be valuable for identifying different source facies characteristics within the same paleolake depositional system

geochemical characteristics across the oxic anoxic interface rote faule front within the kupferschiefer of the lubin sieroszowice mining district sw poland abstract samples of profiles from lower zechstein in the lubin sieroszowice mining district sw poland were collected within and at different distance to the oxidized facies rote faule developed within the zechstein strata around the zary pericline the samples include kupferschiefer underlying weissliegendes sandstone and overlying zechstein limestone from rote faule zones adjacent cu mineralized strata and drill cores from the pb zn mineralized zone more distant to the rote faule front the kupferschiefer samples show differences in ore paragenesis and composition of organic matter which are accompanied by variations in base metal and trace element contents and isotope ratios of organic carbon and carbonates the results from rock eval analyses provide evidence for an oxidative alteration of organic matter in kupferschiefer samples within and adjacent to the rote faule zones related to base metal mineralization the extent of this alteration is reflected by differences in the temperature of maximum pyrolysis yield t max hydrogen and oxygen indices hi oi in contrast to kupferschiefer from pb zn mineralized areas organic matter is characterized by lower hydrogen equivalents and by higher t max values the changes in the isotopic composition of organic carbon and carbonates reflect the alteration of organic matter kerogen within or close to rote faule zones is enriched in 13 c caused by the preferential release of isotopically light organic compounds through progressive degradation of organic matter the opposite tendency towards lower 13 c values of calcite provides evidence for organic matter remineralization isotopic exchange reactions of carbonate with the isotopically distinct oxidizing brines at temperatures between 100 and 120 c caused decreasing 18 o values of calcite the regional zonation in the kupferschiefer with respect to sulfide paragenesis and base metal composition in the mines is explained by metal precipitation from oxidizing brines through decreasing eh conditions during the infiltration of the brines into the reduced kupferschiefer relationships between selected trace elements organic carbon and sulfur contents and hi values are consistent with that model of ore formation

neoproterozoic early cambrian biota and ancient niche a synthesis from molecular markers and palynomorphs from bikaner nagaur basin western india abstract the time frame of present study is neoproterozoic early cambrian an enigmatic and consequential time in the history of earth the present study elucidates the terminal proterozoic biota and palaeoenvironment by characterizing the soluble and insoluble fractions of organic matter extracted from sediment core samples recovered from marwar supergroup bikaner nagaur basin western india the normal alkanes range from c15 to c33 wherein c19 to c21n alkanes predominate and carbon preference index ranges from 1 12 to 1 19 pristane phytane ratio varies between 0 9 and 1 2 the kerogen matter occurs as homogenous laminae and discrete organic remains which are mostly derived from microbial mat triterpenoids include cheilanthanes and hopanes which are confirming evidences of microbial input algal presence has also been confirmed from palynological data green algae evolved to be a major biota during the neoproterozoic early cambrian time and this is validated by the appreciable abundance of c29 steranes in the bitumen fraction the amorphous pieces of kerogen residues lack any visibly distinct internal features however a very few simple ornamented acritarchs like micrhystridium sp lophosphaeridium sp and leiosphaeridia sp are observed in the organic residues micro ftir spectroscopy of the amorphous organic particles reveals the presence of long chain aliphatic components and unusually high c c aromatic ring stretching band the organic remains were deposited in restricted marine water and elevated saline condition as indicated by several salinity biomarkers the present study clearly demonstrates a microbial mat dominated niche with significant eukaryotic green algae that had been capable of surviving in the high salinity of the terminal proterozoic oceans

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

pyrite framboids and their development a new conceptual mechanism it has been suggested that the two morphologies of sedimentary pyrite framboids and euhedra may reflect two distinct pathways of pyrite formation framboids form indirectly via iron monosulphides whereas euhedra form from direct precipitation from solution a third pathway which is bridging these two forms is proposed here namely the continuous growth from a monosulphide globule through framboids to a euhedral single crystal it is also suggested that framboids probably occur over a range of three orders of magnitude from the least complex microframboids through framboids to polyframboids

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

bering sea earthquake of february 21 1991 active faulting along the bering shelf edge on february 21 1991 an ms 6 8 shallow earthquake occurred in the eastern bering sea in an area which previously has shown no significant seismic activity the earthquake was located on the bering shelf close to the shelf edge near one of the elongate basins zhemchug basin that follow the outer shelf to better understand the causes of this unusual event we relocated the earthquake and its aftershocks determined its source mechanism and depth and examined multichannel seismic observations of structures near the epicenter the event was relocated from regional and teleseismic p and s arrival times using a nonlinear inverse technique as were the 19 previous well recorded bering sea earthquakes in global catalogs 1964 1987 the 1991 mainshock epicenter was located on the western flank of zhemchug basin the only four previous events with small 1 location errors relocated at the outer shelf near the pribilof islands the focal mechanism for the 1991 event determined by inversion of teleseismic broadband body waves and centroid moment tensor data shows oblique normal faulting with the t axis oriented north south one nodal plane dips steeply to the northeast and strikes parallel to the basin axis subparallel to faults that bound zhemchug basin this earthquake may be due to slip on one of these normal faults several of which are seen to offset young strata on a multichannel seismic line 30 km south of the earthquake it has previously been suggested that the large canyons that cut the bering shelf and the adjacent outer shelf basins are fault controlled but this event and its aftershocks provide the first strong evidence to support the hypothesis that these structures are currently active and produce earthquakes seismic activity along the bering shelf edge may provide a good explanation for felt reports of several large events in the 1800s that have so far been difficult to associate with interplate activity along the aleutian trench or with any other seismically active structure

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

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

obliquity oblateness feedback are climatically sensitive values of obliquity dynamically unstable a new model is presented for feedback between rotational and climatic variations operative on time scales of 104 107 years due to the combined effect of planetary perturbations to the earth s orbit plane and luni solar torques on the oblate figure of the earth the obliquity varies by 1 on a 4 104 year time scale associated changes in the seasonal and latitudinal pattern of incident solar radiation cause major glaciations mass transport from the oceans to the polar ice sheets during these glaciations can change the gravitational oblateness of the earth by amounts approaching 1 as the rate of spin axis precession is directly proportional to the oblateness the climatically forced mass transport can by dynamically significant a simple parameterization of us coupled orbital rotational climatic system suggests that there is a strong tendency for the system to evolve away from climatically sensitive values of the obliquity this may explain the mid pleistocene transition from an obliquity dominated regime to the present regime in which most climatic variability is concentrated at longer 105 year periods

phenyldibenzofurans and phenyldibenzothiophenes in marine sedimentary rocks and hydrothermal petroleum abstract the phenyl derivatives of dibenzo b d furan and dibenzo b d thiophene so far not reported in geological samples have now been identified in some sedimentary rocks bitumen and hydrothermal petroleum through a comparison of their retention times and mass spectra with those of authentic standards all four possible positional isomers were detected for each phenyldibenzo b d furan phdbf and phenydibenzo b d thiophene phdbt their elution sequence is 1 4 2 and 3 phenyldibenzo b d furan and 1 4 2 and 3 phenyldibenzo b d thiophene on apolar stationary phases in contrast to phenyldibenzofurans the distributions of the thiophene series is controlled mainly by the organic matter maturity in the most mature samples 4 2 and 3 phdbts prevail over 1 phdbt while less mature samples contain mainly 4 phdbt or 1 phdbt and 2 3 phdbts occur at comparable concentrations however in samples of low maturity in addition to the phenyldibenzo b d thiophene c 18 h 12 s series other structural isomers of c 18 h 12 s possessing very similar mass spectra were detected these are likely to be either naphthylbenzo b thiophenes and or phenylnaphtho b thiophenes phdbfs and phdbts are likely to be intermediate products in the formation of more condensed heterocyclic polycyclic aromatic compounds like triphenyleno 1 12 bcd thiophene and triphenyleno 1 12 bcd furan and benzobisbenzofurans and benzobisbenzothiophenes which are commonly detected in geological samples

c40 monoaromatic lycopane derivatives as indicators of the contribution of the alga botryococcus braunii race l to the organic matter of messel oil shale eocene germany abstract a novel series of sedimentary aromatic lycopane derivatives cyclolycopatrienes has been found in an outcrop sample from the messel oil shale the predominant monoaromatic compound 4 from this hydrocarbon series has been isolated using reversed phase hplc and its structure determined using 1d and 2d 1h nmr spectroscopy as well as from identification of the ruo4 degradation products from examination of its structure related to that of lycopane and from its stable carbon isotopic composition this compound and related isomers can be considered as new proxies for botryococcus braunii race l in sediments deposited under freshwater and or brackish conditions

polycyclic alkanes in a biodegraded oil from the kelamayi oilfield northwestern china abstract a comparison is made of the distributions of certain classes of saturated hydrocarbon biomarkers in an unaltered oil and a severely biodegraded oil from the kelamayi oilfield in the zhungeer basin of northwestern china both oils are thought to have the same source rock the n alkanes acyclic isoprenoids carotenoid derived alkanes and regular c27 c29 steranes which are present in the nondegraded oil were not detected in the biodegraded sample additionally the biodegraded oil shows an increase in the abundance oil and the presence of 17 h 25 norhopanes 17s h 25 norhopanes c 10 demethylated tricyclic terpanes and a c 10 demethylated c23 tetracyclic terpane which were not detected in the nondegraded oil c26 and c25 regular steranes appear to show a much greater resistance to microbial attack than the c27 c29 regular steranes as indicated by an isomer distribution for these low molecular weight steranes that is expected for nondegraded samples in the biodegraded oil unknown tricyclic compounds showing a base fragment ion of m z 219 and a similar carbon number abundance to the steranes in the nonbiodegraded sample are present in relatively high concentrations in the biodegraded oil these compounds are also present in very low abundance in some nondegraded oils from the kelamayi basin indicating that their much higher concentration in the microbialy altered oil is possibly due to their resistance to biodegradation however at present their derivation from the microbial alteration of steranes cannot be ruled out several series of bicyclic compounds are also present in higher concentrations in the biodegraded oil

the role of organically bound sulphur in stratiform ore sulphide deposits abstract low and high molecular weight organic sulphur compounds were analyzed in a selected number of samples of the permian kupferschiefer poland their significant presence in these mature samples supports the hypothesis that during deposition and shortly thereafter labile organic sulphur compounds must have been very abundant this assumption has led to a new model for metal accumulation based on a slow and gradual release of sulphur from these labile organic sulphur compounds during increasing diagenesis

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

accumulation of copper in the permian kupferschiefer a result of post depositional redox reactions abstract within the central european zechstein basin the permian kupferschiefer has been deposited under anoxic conditions in most parts of the basin the metal content does not exceed values commonly observed in black shales however in areas near to the zechstein sea shore which are simultaneously related to rift zones a significant base metal enrichment is observed organic geochemical analyses of the copper mineralized sections in the kupferschiefer from southwest poland show that significant changes in the composition of organic matter are associated with the metal enrichment processes porphyrins commonly abundant constituents of the shale have been decomposed by oxidizing fluids additionally aliphatic hydrocarbons have been largely removed from the bitumen and alkylated aromatic systems were affected by side chain degradation this particular type of alteration is explained by ascending oxidizing solutions which transported high amounts of base metals from lower permian red beds into the kupferschiefer horizon acting as a geochemical trap the metal precipitation is suggested to be a result of thermochemical sulphide production with organic matter acting as hydrogen source in areas such as the lower rhine basin in the bottom section of the kupferschiefer the base metals lead and zinc as well as barium have been accumulated from basinal carboniferous formation waters copper enrichment is not observed because potential source rocks are missing in this area however the observed compositional changes of the organic matter do not point towards thermochemical redox processes

flash pyrolysis of kerogens from algal rich oil shales from the eocene huadian formation ne china abstract the hydrocarbon composition of the kerogen fractions of two samples hd 20 and hd 21 from oil shale layer 4 in the eocene huadian formation ne china were investigated by analytical flash pyrolysis 650 c 10 s followed by gas chromatography mass spectrometry py gc ms organic petrography showed that the two kerogens were almost entirely derived from algal remains but contained very different algal maceral compositions with 40 of the macerals in hd 20 being of macroalgal origin that were not present in hd 21 py gc ms yielded high concentrations of n alkanes from both kerogens but with different molecular weight profiles due to the different algal contributors to the two kerogen samples the hydrocarbon pyrolysates generated at 650 c from hd 21 in which the green microalga botryococcus braunii was identified showed a higher proportion of longer chain alkanes and alkenes presumably from cracking of the botryococcus algaenan we also identified a c40 monoaromatic lycopane derivative which was absent in the hd 20 the high hydrocarbon potential of both kerogens can be attributed to common microalgal sources whereas the macroalgae which is abundant in hd 20 makes only a minor contribution to the hydrocarbon products

sensitivity of biomarker properties to depositional environment and or source input in the lower toarcian of sw germany abstract a sequence of lower toarcian sediments which are highly contrasting in their depositional environment over a 5 m depth interval has been investigated in detail for the variability of geochemical properties which are used for source characterization and oil to source correlation lower liassic marls are representative of a well aerated shallow water environment in contrast to the immediately overlying bituminous shales which are deposited under extremely reducing conditions various properties have been found to vary considerably within these two units amongst the most important are carbon isotopic composition of the kerogen the pristane phytane ratios nickel as opposed to vanadyl porphyrins and the c27 dia regular steranes although maturation within the profile does not change some of the maturation dependent biomarker properties such as the monoaromatic steroid side chain cracking and the tm ts ratio exhibit large changes which can be assigned to diagenetic processes another maturation dependent property the 20s 20r epimerization of c29 steranes exhibits smaller changes which could also be due to early diagenetic processes the study suggests that reducing and oxidizing conditions i e eh and ph in the sediment exert an influence on several biomarker precursor product pathways in maturation studies initial variations due to depositional conditions have therefore to be taken into account

distribution of isoprenoid hydrocarbons and alkylbenzenes in immature sediments evidence for direct inheritance from bacterial algal sources abstract alkanes having unusual saturated isoprenoidal and methyl branched structures have been isolated from the bitumen of several sediments the methanogenic biomarkers 2 6 10 15 19 pentamethyleicosane and squalane were found in sediments which also contained bacteriogenic glycerol ethers however in one ether containing sediment 2 6 10 13 17 21 hexamethyldocosane was tentatively identified and this compound was found in place of the established alkane biomarkers other hydrocarbons found were regular c21 and c23 isoprenoid alkanes compounds which cannot be derived from phytol two isoprenoids of the type 3 7 11 polymethylalkane previously reported only in petroleums 8 methylheptadecane a probable biomarker for cyanobacteria and a number of its homologs and other methyl branched alkanes ubiquitous branched chain alkylbenzenes and a homology of trimethylalkylbenzenes were also isolated most or all of the compounds reported here are probably not catagenetic products but may represent direct algal or bacterial bioinputs

molecular indicators of palaeoenvironmental conditions in an immature permian shale kupferschiefer lower rhine basin north west germany from free and s bound lipids a study of the distributions of free and s bound biomarkers and their 13c values in the extract of a bulk sample of the permian kupferschiefer from the lower rhine basin has been carried out to provide a more detailed characterization of the biological inputs the distributions and isotopic compositions of selected components released from nickel boride desulphurization have been compared with those of components in the free fraction the free biomarkers occur in greater abundance than their s bound counterparts the distribution and carbon isotopic composition of both free and bound components in the extract indicate a major cyanobacterial and algal input likewise the free and bound aromatic hydrocarbons contain components which reveal an origin from the carotenoids of chlorobiaceae green sulphur bacteria providing molecular evidence for the occurrence of photic zone anoxia in the water column most of the components in the complex mixture of mono di tri and tetra aromatics in the free aromatic hydrocarbon fraction result from cyclization and aromatization reactions

the werra cyclotheme upper permian fore sudetic monocline poland insights into fluctuations of the sedimentary environment from organic geochemical studies abstract a study of the extracts of samples recording a transgressive regressive succession of the werra cyclothem zechstein upper permian from the southern margin of the european permian basin the fore sudetic monocline poland provides an insight into major sources of organic matter and diagenetic processes the studied cross section comprises all lithologies representative for the european basin including transgressive sandstones weissliegend and organic rich shales kupferschiefer followed by carbonates as well as regressive anhydrites with intercalations of rock salt due to the variable influence of overlapping diagenetic processes that affected the organic matter i e maturation and late diagenetic oxidation related to base metal mineralisation a reliable comparison of the biomarker results is only possible for the major upper part of the section ca 38 m including carbonates and evaporites but not for the oxidised first 2 3 m from the base of the kupferschiefer the transition from carbonate to evaporate sedimentation is associated with a shift to predominant even c numbered n alkanes increased abundance of carotanes and high homohopane index reflecting enhanced reducing conditions the presence of the c25 regular isoprenoid squalane biphytane and the rapid decrease in the pristane phytane ratio in the evaporites are mainly controlled by the important contribution from both halophilic and methanogenic archaea the occurrence of gammacerane in the anhydrites suggests development of water column stratification at some stages of the sea regression this is associated with appearance of specific aryl isoprenoids with a lycopane carbon skeleton most likely related to botrycoccus braunii race l algae lycopane derivative occurrence suggests that such an algal race could have occurred since permian currently known recent eocene the presence of the abundant freshwater brackish algal biomarkers in evaporititic deposits can be envisaged in the costal part of the zechstein basin with temporary salt wedge estuary water stratification the algae bloomed in the top fertile fresh brackish water layer fed by rivers and the algal biomass was deposited on the sea floor covered with evaporitic brine the stratification periodically broke down during precipitation of the rock salt presumably due to a decrease in riverine water input as revealed by characteristic disappearance of gammacerane and hopane distributions similar to those observed for the carbonate rocks the methylphenanthrenes phenanthrene ratio was used together with methyldibenzothiophenes dibenzothiophene ratio to assess maturity these maturity estimations indicate that the peak of oil window has been reached which is confirmed by other biomarker maturity parameters based on sterane and hopane distributions the maturity stage of oil generation and expulsion was further confirmed by the presence of solid bitumen as cements in the sandstone underlying kupferschiefer and bitumen veins and lenses in the carbonates

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

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

biomarker geochemistry of a foreland basin the oligocene menilite formation in the flysch carpathians of southeast poland black shales of the menilite formation the source rock for oils in the carpathian overthrust belt display a large variability in their bulk and molecular geochemical parameters biomarker and stable carbon isotope analyses indicate a variable contribution from different algae particularly dinoflagellates and diatoms and cyanobacteria this is reflected by specific predominantly sulfurised biomarkers e g c35 homohopanoids c25 highly branched isoprenoids and marine n alkanes and by particular distributions of steranes and 4 methylsteranes comprising 24 nor and 24 methyl 27 norcholestanes and related novel steranes with a methylation at c 23 the presence of hopanoids of methanotrophic origin 13c up to 57 implies a temporarily enhanced full methane cycle in a marine environment which affected the isotopic composition of organisms dwelling in the upper photic zone the presence of isorenieratene derivatives indicate periods of euxinic conditions within the photic zone in all investigated sub basins

organic geochemistry depositional history and hydrocarbon generation modelling of the upper permian kupferschiefer and zechstein limestone strata in south west poland abstract the upper permian zechstein limestone carbonates in the south western part of the polish zechstein basin contain small quantities of organic matter usually less than 0 1 wt toc and have poor hydrocarbon potential in contrast the kupferschiefer shales have excellent hydrocarbon potential with toc as high as 10 8 wt predominantly algal type ii kerogen generally thermal maturity of the organic matter is 0 6 0 9 vitrinite reflectance while locally is as high as 1 45 the kimmerian and laramian tectonic events significantly influenced the regional burial and thermal history the main subsidence of the kupferschiefer zechstein limestone complex took place during the late permian late triassic period with additional burial during the jurassic and late cretaceous hydrocarbon generation from the kupferschiefer source rocks occurred from middle triassic to late jurassic times reaching maximum rates during the jurassic the cretaceous subsidence had only a minor influence on the maturity and transformation of organic matter expulsion started between late triassic in the western part of the study area and early jurassic in the eastern part then ceased by the late jurassic early cretaceous erosion the total amount of generated and expelled hydrocarbons from source rocks was small because their thickness was limited therefore kupferschiefer shales cannot be considered as source rocks for liquid hydrocarbons but may be a potential source for gas accumulated in the zechstein limestone and rotliegend reservoirs

generation of nitrogen and methane from sedimentary organic matter implications on the dynamics of natural gas accumulations nitrogen n2 contents of natural gases in rotliegend and buntsandstein reservoirs of the north german basin regionally approach 100 a review is given of the various hypotheses primordial origin volcanic or magmatic origin radiogenic origin atmospheric origin organic origin inorganic nitrogen in sedimentary rocks presented to account for nitrogen anomalies in this area and other parts of the world the objective of the present study was to investigate sedimentary organic matter in particular coals as a potential source of molecular nitrogen in the subsurface comparison of reservoir sizes and gas generation potentials indicates that carboniferous coal measures which are considered as the source of the natural gas in the north german basin can readily account for the nitrogen quantities found in present day reservoirs laboratory pyrolysis experiments were carried out to investigate the kinetics of generation of methane and molecular nitrogen from coals of different type and rank under experimental conditions nitrogen is formed at higher temperatures than methane supporting the concept of a fractional generation of methane and nitrogen in natural systems based on the kinetic parameters derived from laboratory experiments methane and nitrogen generation rates from coals were calculated for geologic heating rates gas containing more than 50 nitrogen is generated under these conditions at temperatures in excess of 300 c nitrogen rich gases are thus formed only in the final stage of gas generation after methane generation has practically ceased it is concluded that the amounts of gas encountered in nitrogen rich gas accumulations represent only a small fraction possibly 1 of the total gas generation potential of this area while the bulk of the generated gas has escaped to the atmosphere the present day composition of the reservoir gases reflects the composition of only the most recently generated gas on a geologic time scale

organic matter maturity and hydrocarbon potential of the lower oligocene menilite facies in the eastern flysch carpathians tarcău and vrancea nappes romania abstract bulk organic geochemical and molecular composition data have been used to analyse the hydrocarbon potential and organic matter maturity of the lower oligocene menilite facies from two adjacent tectonic units of the eastern flysch carpathians tarc u and vrancea nappes romania due to the importance of these source rocks in hydrocarbon exploration in entire paratethys realm the data show strong variability in organic matter quantity and quality organic carbon content reaches peak values in the siliceous facies of the lower menilite member up to 8 6 wt toc which contains type ii kerogen with increasing contribution of flysch sedimentation mixed type ii iii kerogen gains importance the biomarker distribution reveals strong variation in the supplied organic matter common for flysch influenced sedimentary environments terrigenous input is marked by epicuticular wax imprint in n alkane distribution and occurrence of conifer biomarkers while marine organic matter origin is expressed by the occurrence of short chain n alkanes and hopanes especially in the siliceous facies thus these source rocks can be classified as oil prone and subordinately mixed oil gas prone the maturity in the outer tectonic unit vrancea is low t max 425 c r o 0 4 but increases towards the inner tarc u nappe t max 430 c r o 0 5 reaching onset of hydrocarbon generation the studied rocks have good petroleum potential but hydrocarbons were generated only in more mature tarc u nappe where solid bitumen veins were observed bitumen impregnation of numerous vitrinite grains possibly suppressed vitrinite reflectance thus leading to more accurate maturity assessment based on molecular proxies biomarker maturity indices the observed difference in maturity levels between the nappes results from the more inner position of the sampled tarc u nappe succession within the orogen relative to the vrancea unit this is related to different burial histories as well as variation in subsequent erosion and exhumation levels the actual hydrocarbon potential in the studied area varies due to local interplay of these critical factors

unusual distributions of long chain alkenones and tetrahymanol from the highly alkaline lake van turkey long chain c37 to c40 alkenones with di tri and tetra unsaturation are very abundant in sediment trap material and holocene to late pleistocene core samples from the earth s largest soda lake lake van turkey thus the known distribution range of these typical biomarkers for haptophyte microalgae is extended to highly alkaline environments the observed unsaturation patterns differ strikingly from those found in open marine haptophytes and sediments by an enhanced relative abundance of the tetra unsaturated compounds especially the c37 4 methyl ketone their preponderance is suggested to be a facies marker pattern for lacustrine and marginal marine areas of sedimentation using published u37k calibrations no reliable absolute temperatures were obtained for the lake van samples accordingly marine sea surface temperature determinations based on long chain alkenones should be applied with caution when a contribution of these compounds from coastal or nonmarine sources can not be excluded the presence of tetrahymanol and gammacer 3 one in the lake van materials is attributed to organic matter contributions of ciliates the relative abundance of long chain alkenones and of tetrahymanol gammacer 3 one is considered to reflect changes in the environmental conditions in particular in the hydrological setting we suggest that times of pronounced stagnation are recognised by very high tetrahymanol gammacer 3 one concentrations together with drastically increased stanol stenol ratios and intervals of enhanced convection or of high freshwater input are characterised by high alkenone contributions

geochemical and isotopic composition of organic matter in the kupferschiefer of the polish zechstein basin relation to maturity and base metal mineralization vs the present depth of the kupferschiefer soluble organic matter som yields and relative proportions of saturated and aromatic hydrocarbons of the som provide evidence for an oxidative alteration of organic matter in highly mineralized kupferschiefer samples near the rote faule zones this is confirmed by differences in the composition of the saturated and aromatic hydrocarbon fractions of the soluble organic matter saturated hydrocarbons from rote faule samples are dominated by short chain n alkanes and higher abundances of pristane and phytane relative to heptadecane n c17 and octadecane n c18 respectively compared with samples more distant to the rote faule zone compositional changes of the aromatic hydrocarbon fractions with decreasing distance to that zone are characterized by the occurrence of polycyclic aromatic hydrocarbons and elevated ratios of phenanthrene to methylphenanthrenes that are attributed to demethylation reactions and resulted in a decrease of the methylphenanthrene index mpi 1 kupferschiefer samples from the barren zone of the polish basin do not show these alteration patterns the observed variations in organic matter composition with burial depth are consistent with changes due to increasing thermal maturation maturity assessment is achieved from mpi 1 and the methyldibenzothiophene ratio mdr from the relationship between the maturity of organic matter in terms of vitrinite reflectance values and depth of the kupferschiefer strata a continuous increase in reflectance of vitrinite is obtained within the polish basin the alteration pattern of organic matter related to base metal mineralization of the kupferschiefer corresponds to changes in the isotopic composition of organic carbon and calcite kerogen within or close to rote faule zone is enriched in 13c caused by the preferential release of isotopically light organic compounds through progressive degradation of organic matter the opposite tendency towards lower 13c and 18o values of calcite provides evidence for isotopic exchange between carbonate and the oxidizing ore bearing solutions and for organic matter remineralization in contrast organic matter and calcite from the kupferschiefer do not show regular trends in 13c with increasing thermal maturation