palaeoenvironment of the eocene eckfeld maar lake germany implications from geochemical analysis of the oil shale sequence abstract drill core samples from the depth interval between 19 4 and 32 0 m of the laminated central lake facies of the eocene eckfeld maar were investigated for biomarker and stable isotope composition bulk organic geochemical parameters c n hi and the molecular composition of the soluble organic matter indicate a dominance of particulate organic matter from land plants and microbially derived lipids in the lower part of the sedimentary succession an angiosperm dominated vegetation is indicated from the terpenoid biomarker composition abundant 4 methylsteroids in the 25 6 30 8 m section of the oil shale sequence reflect a contribution of algal derived biomass samples with high concentrations of methylsteroids are characterized by low amounts of triterpenoids related to the arborane skeleton and vice versa this pattern is interpreted as reflecting differences in autochthonous organic matter production vs microbial activity in the lowermost section 32 0 30 6 m a trend towards heavier 18 o and 13 c values indicates the evolution of permanently meromictic conditions in the lake and an increase in methanogenesis high 13 c values of siderites 10 throughout most of the sequence are consistent with permanently anoxic conditions at the sediment water interface the lighter 18 o values of siderites from turbidites relative to siderites from biogenic laminites are postulated to have been caused by temporary phases of increased precipitation followed by landslides and improved circulation within the lake depletion of the organic matter in 13 c average 13 c 29 4 in comparison with the fossil wood ranging from 23 1 to 26 6 is explained by the dominance of waxy lipid rich land plant material e g leaf waxes resins bark over wood supplied to the lake carbon cycling during anoxic decomposition of organic matter is assumed to further affect the 13 c values through the activity of anaerobic e g methanogenic bacteria resulting in a depletion of the biomass in 13 c the overall trend in the isotopic composition of organic carbon towards heavier values in the depth interval between 26 0 and 3 2 m is accompanied by decreasing c n ratios indicating an increase in aquatic organic matter production the geochemistry of the oil shale succession points towards a highly productive eutrophic ecosystem with intense microbial activity under meromictic conditions in the maar lake beside the high input of land plants to the biomass major contributions from bacteria and phytoplankton are indicated by the biomarker composition

sources and occurrence of c12c22n alkane distributions with even carbon number preference in sedimentary environments abstract the occurrence of c12 c22n alkanes with a strong even carbon number preference is reported in recent and miocene sediments encompassing marine and freshwater systems deposited under oxic and anoxic conditions it is therefore shown that these n alkanes can be found in a wider type of sedimentary environment than those previously described the occurrence in some cases of a parallel distribution of c14 c20n alk 1 enes is also illustrated a variety of biological sources including both marine and freshwater bacteria as well as fungi and yeast species is suggested to account for such distributions

comparative studies of organic matter petrography of the late palaeozoic black shales from southwestern poland abstract there are at least two sapropelic units associated with late palaeozoic black shales in central europe the older unit of late carboniferous age is the lower part of the anthracosia shales in the intrasudetic basin and the younger one is the well known zechstein kupferschiefer in both the foresudetic monocline and the northsudetic basin the first unit is of lacustrine origin while the second one represents deposition in a shallow marine depositional environment both units contain high amounts of organic matter thus being typical black shales the organic matter dispersed in these shales was studied petrographically in general the vitrinite reflectance of the shales studied indicates variable but moderate organic matter maturity 0 68 1 25 equivalent to the oil window detailed microscopic studies of the organic material dispersed in the lower unit of the anthracosia shales showed that liptinite especially alginite is the most abundant component secondary altered organic matter i e solid hydrocarbons rarely occurs organic components together with mineral matter constitute a lacustrine sapropelic association a humic terrestrial association and an intermediary association the character and predominance of alginite and lacustrine sapropelic association are indicative of an open lacustrine depositional environment in general this organic composition is typical of type i kerogen microscopic analysis of the kupferschiefer revealed a mixture of liptinite vitrinite and inertinite macerals and other organic components such as amorphous sapropelic mass asm and solid bitumens the most common organic components are liptinite macerals bituminite and alginite predominate and are diagnostic macerals of this unit the amount of bituminite locally exceeds 85 vol other liptinite macerals such as sporinite and liptodetrinite are present in significantly lower amounts one exception being asm which may be present in higher amounts humic constituents vitrinite and inertinite are rare present in small amounts in the kupferschiefer beds the organic matter composition points to type ii kerogen for this unit

biomarker distributions in australian oils predominantly derived from terrigenous source material oils found in many australian sedimentary basins contain a relatively high input of terrigenous organic source material a study of a large number of these oils has permitted a number of biomarker distributions to be determined that appear to be characteristic for oils derived from terrigenous source material these features include the presence of sesquiterpanes absence of tricyclic terpanes relatively high concentrations of a c24 tetracyclic terpane predominance of c29 steranes presence of two unidentified c27 and c30 terpanes and virtual absence of 18 h oleanane the latter observation is significant since it appears that 18 h oleanane appears only in oils of tertiary age derived from terrigenous source material an attempt has also been made to compare the results for the australian oils with published results for oils derived from terrigenous source material in other parts of the world the number of reports in the literature for these oils is fairly limited but it appears that some of the observations for the australian oils can be extended to them this study is an initial attempt to devise a classification scheme that can be used to determine the origin of an oil unambiguously from biomarker parameters in order for this approach to be successful a relatively large number of biomarker parameters need to be assigned as characteristic of a particular type of source material

oligocene miocene source rocks of the zhongcang basin implications for hydrocarbon potential differentiation between lake basins in central tibet abstract the oligocene miocene dingqinghu formation is widely distributed in lake basins of the bangong nujiang suture zone bnsz central tibet and has been reported as an important source rock layer however limited works have been conducted in the zhongcang basin to gain knowledge on hydrocarbon potential of this area and further investigate the organic matter om accumulation mechanisms of source rocks in the bnsz basins samples collected along two measured sections from the zhongcang basin were subjected to sedimentological organic geochemical and petrographic analyses sedimentological analyses indicate that all samples were deposited in prodeltic to deep lake environments total organic carbon toc values and pyrolysis data suggest a poor to fair hydrocarbon source potential of the middle dingqinghu formation with the exception of om rich samples locate in a marker bed of the upper part vitrinite reflectance ro values of the upper part and middle lower part samples range from 0 41 to 0 50 and 0 52 to 0 61 indicating immature and marginal mature stages respectively these maturity levels were also supported by specific maturity indices of sample extracts such as ratios of c31 22s 22s 22r homohopanes and c29 steranes bulk geochemistry maceral composition of kerogen and extract biomarkers demonstrate that om rich samples were deposited in fresh to brackish waters with type ii iii kerogen mainly derived from algae and higher plants while poor to fair samples have less higher plant contribution but relatively high bacterial content that probably originated from more saline environments the paleoclimate induced environmental reorganization is likely responsible for the differential om accumulation in the zhongcang basin relatively wet climates would facilitate primary productivity of the lake as well as development of swamps on the delta resulting in deposition of mixed terrestrial and aquatic om with higher toc whilst dry conditions would restrict the development of river systems and promote the establishment of saline environments causing decreased total om input but increased proportion of halophilic bacterial om in addition we summarized published data of the dingqinghu formation in the bnsz basins and preliminarily reconstructed paleogeography of central tibet two types of drainage patterns were confirmed in this area a long lived hierarchical drainage system is developed in the lunpola area while single lake systems were prevalent in other basins including the zhongcang basin the hierarchical drainage pattern could minimize clastic dilution effects during tectonic active and or relatively wet periods and prevent the establishment of hypersaline environments during the dry period the drainage center in this kind of hierarchical system has lower sedimentation accumulation rate and could receive much more aquatic om at any climatic conditions we argue that tectonic induced drainage organization primarily controlled the hydrocarbon potential differentiation between lake basins of central tibet

organofacies and paleoenvironment of lower carboniferous mudstones dishuiquan formation in eastern junggar nw china abstract the sedimentary rocks of the dishuiquan formation represent an important potential source for volcanic rock reservoirs and record the transition of the depositional environment from marine to terrestrial during paleo junggar oceanic subduction the source rock potential and paleoenvironment of mudstones from dishuiquan formation in eastern junggar were determined by organic petrography rock eval molecular and stable carbon 13 c analyses toc s 2 and hydrogen index hi values suggest a fair to good organic richness in mudstone samples from the c 2 well moreover an early mature to mature state for all the samples is inferred based on the rock eval and biomarker parameters the maceral composition molecular geochemistry and carbon isotopic results for kerogen reveal that all the mudstone samples are characterized by a mixed organic matter assemblage types ii iii with relatively high percentages of terrigenous organic matter the low to intermediate values of pr ph and the high abundances of carotene and gammacerane indicate the presence of a dysoxic reducing high salinity sedimentary environment during the deposition of the dishuiquan formation numerous parameters derived from the organic geochemical analyses indicate that the terrigenous organic matter increased with decreasing salinity and oxidation in the sedimentary environment this study concludes that a warm wet climate provided a continuous fluvial input of terrigenous plant debris and fresh water the organic geochemical data combined with the tectonic setting reveal a restricted semi closed marine depositional environment during the deposition of the dishuiquan formation in the early carboniferous

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

organic geochemical characteristics and depositional environments of the jurassic coals in the eastern taurus of southern turkey abstract in this study organic matter content type and maturity as well as some petrographic and physical characteristics of the jurassic coals exposed in the eastern taurus were investigated and their depositional environments were interpreted the total organic carbon toc contents of coals in the feke akkaya kozan gedikli and kozan kizilinc areas are 24 54 66 78 and 49 15 respectively the feke akkaya and kozan kizilinc coals have low hydrogen index hi values while the kozan gedikli coals show moderate hi values all coal samples display very low oxygen index oi values the kozan gedikli coals contain type ii organic matter om the feke akkaya coals contain a mixture of type ii and type iii om and the kozan kizilinc coals are composed of type iii om sterane distribution was calculated as c27 c29 c28 from the m z 217 mass chromatogram for all coal samples tmax values for the feke akkaya kozan gedikli and kozan kizilinc coals are 439 412 and 427 c vitrinite reflectance values ro for the feke akkaya and kozan kizilinc coal samples were measured as 0 65 and 0 51 and these values reveal that the feke akkaya and kozan kizilinc coals are at subbituminous a or high volatile c bituminous coal stage on the basis of biomarker maturity parameters these coals have a low maturity the pristane phytane pr ph ratios for the feke akkaya kozan gedikli and kozan kizilinc coals are 1 53 1 13 and 1 25 respectively in addition all coals show a homohopane distribution which is dominated by low carbon numbers and c35 homohopane index is very low for all coal samples all these features may indicate that these coals were deposited in a suboxic environment the high sterane hopane ratios with high concentrations of steranes low pr ph ratios and c25 c26 tricyclic ratios 1 may indicate that these coals formed in a swamp environment were temporarily influenced by marine conditions

stable hydrogen isotopes of bison bone collagen as a proxy for holocene climate on the northern great plains abstract isotopic analyses of fossil and archaeological bison remains can provide information about the biology of prehistoric bison and the ecological conditions in which they lived hydrogen isotope ratios 2h 1h measured as d of bison bone collagen should ultimately reflect through bison diet those average ratios of local precipitation which vary systematically according to location and climate to confirm this d values were measured from bone collagen samples collected from geographically distinct populations of modern bison in north america the d values of these groups differed in a manner consistent with that of the modern isotopic and climate gradients at each geographic location archaeological bison bone samples representing eight temporally distinct populations covering early middle and late prehistoric age sites from southern saskatchewan were collected and analyzed while the mean d value of each group was consistent with variations in hydrogen isotope composition observable from precipitation in the northern plains significant differences were found between some of the sampled cohorts these differences represent climate differences at each of the sampled time periods the temporal climatic patterns revealed by the d values of prehistoric bison population bone collagen compares favourably with other models of southern saskatchewan holocene climate change as reconstructed using other proxy climate archives the d values of bone collagen from prehistoric bison demonstrate a potential for use as a specific paleoclimate proxy which can be directly linked to the 14c age and lifetime of the sampled animal

liptinite as an indicator of environmental changes during formation of coal seam no 207 upper silesia poland the coal seam no 207 was a subject of palynological and petrographic studies according to the results of the vitrinite random reflectance measurements supplemented by moisture and calorific value determinations the rank of this coal is matching the boundary between sub bituminous and bituminous coals the aim was to reconstruct the environmental conditions during the biochemical stage of seam formation as well as the facies development throughout the seam profile the maceral incident and fluorescence mode and microlithotype compositions incident light supplemented by palynological analyses show that there were two main facies developments in the authors opinion they correspond with a phase of ombrogenous raised bog marked by the presence of crassidurite with densosporites variabilis and a wet forest swamp phase represented by vitrite and clarite with more diverse spore assemblage including densospores other minor but distinctive sediments a cannel layer and a reeds facies both occurring in the lower part of the seam above the tonstein horizon a dry forest type of sedimentation is recognized

distribution isotopic variation and origin of sulfur in coals in the wuda coalfield inner mongolia china abstract this paper describes coal petrographic characteristics sulfur abundance distribution and isotopic signature in coals in the wuda coalfield inner mongolia northern china petrographic studies suggest that depositional environment influences petrographic composition the no 9 and no 10 coal seams which are thought to have formed on a tidal delta plain have high collodetrinite contents up to 66 1 indicating enhanced gelification and bacteria activity during coal accumulation and also have the highest sulfur content 3 46 and 3 42 both organic and pyritic sulfur isotope values 12 3 to 5 8 and 18 7 to 1 1 respectively are variable and generally tend to be more negative in high sulfur coals than those in low sulfur coals in the wuda coalfield the negative sulfur isotope values indicate that a large portion of sulfur in the high sulfur coals has a bacterial origin sulfur isotopic compositions and variations within the section were used to propose a model to explain the origin of sulfur in these coals the presence of pyritized rod like bacteria cyanophyte s gelatinous sheaths and degraded algae organic matter suggests that bacteria and perhaps algae may play an important role in the formation of these high sulfur coals

surface analysis of pyrite in the no 9 coal seam wuda coalfield inner mongolia china using high resolution time of flight secondary ion mass spectrometry abstract the chemical composition of pyrite in coal can be used to investigate its geological and mineralogical origin in this paper high resolution time of flight secondary ion mass spectrometry tof sims was used to study the chemical composition of various pyrite forms in the no 9 coal seam st d 3 46 from the wuda coalfield inner mongolia northern china these include bacteriogenic framboidal massive cell filling fracture filling and nodular pyrites in addition to fe 54fe 56fe 57fe other fragment ions were detected in bacteriogenic pyrites such as 27al si 28si 29si 30si 40ca cu 63cu 65cu zn 64zn 66zn 67zn 68zn ni 58ni 60ni 62ni and c3h7 tof sims images show bacteriogenic pyrites are relatively rich in cu zn and ni suggesting that bacteria probably play an important role in the enrichment of cu zn and ni during their formation intense positive secondary ion fragments from framboidal aggregates such as 27al 28si 29si alo ch2 c3h3 c3h5 and c4h7 indicate that formation of the framboidal aggregates may have occurred together with clay mineral and organic matter which probably serve as the binding substance the intense ions of 28si and 27al from massive pyrites also suggest that their pores incorporated clay minerals during crystallization together with the lowest 28si 23na value the intense organic positive secondary ion peaks from cell filling pyrites such as c3h3 c3h5 c3h7 and c4h7 indicate that pyrite formation may have accompanied dissolution or disintegration of the cell the intense p peak was observed only in the fracture filling pyrite and the highest 28si 23na value of fracture filling pyrite reflects its epigenetic origin together with xrd and rees data the stronger 40ca in nodular pyrite than other pyrite forms shows seawater influence during its formation

concentration and mode of occurrence of trace elements in marine oil shale from the bilong co area northern tibet china abstract the bilong co oil shale zone is located in the south qiangtang depression this zone together with the shengli river changshe mountain oil shale zone in the north qiangtang depression northern tibet plateau represents a potentially large marine oil shale resource in china with the aim of better understanding geochemistry of marine oil shale 18 samples from the bilong co area are studied and 56 elements in them are determined the contents of mo se cd cs as bi u rb pb th li sr and zn are enriched from 1 3 to 35 0 times as compared with the average concentration in the crust clarke values whereas the other elements are slightly higher lower than the respective clarke values compared to common australian oil shales the contents of ce co cs f ga hf nb nd pb pr rb sc sn th and zr in the bilong co oil shale samples exhibit relatively high levels whereas as br cd cr cu dy er eu ho lu mo ni se tb tm u v y yb and zn are relatively depleted however the distribution patterns of trace elements are quite similar indicating that trace element speciation in oil shale is governed by general processes rather than by individual geochemical mechanisms within one particular sample the elements in the bilong co oil shale may be classified into three groups of association according to their modes of occurrence i e groups a b and c group a si al k na ti zr sc th sn nb ga ta be hf cs li rb ash rees is strongly correlated with ash yield and mainly has an inorganic affinity group b cr w mg mn br f sr ba has weakly or negatively positive correlation coefficients with an exception of f with ash yield group c zn bi cd ca fe pb hg co cu ni p mo se u as v shows negative correlation coefficients with ash yield with an exception of bi and possibly has an organic affinity

tectonic evolution of the early mesozoic blueschist bearing qiangtang metamorphic belt central tibet this is the published version copyright 2003 american geophysical union all rights reserved

sedimentary and organic geochemical investigation of tertiary lacustrine oil shale in the central tibetan plateau palaeolimnological and palaeoclimatic significances article i nfo the zhuonai lake and lunpori oil shale located in the central tibetan plateau were deposited in a tertiary lacustrine environment in the hoh xil and lunpola basins respectively a combined investigation of sedimentary organic geochemistry and organic carbon isotope was performed to define source rock potential the palaeoenvironment and source of the organic matter three types of facies sequences are developed in the zhuonai lake section and oil shale mainly occurs in the oil shale marl sequence the oil shale silty claystone and oil shale marl facies sequences are developed in the lunpori section both oil shales are finely stratified especially for the lunpori oil shale with thickness of the laminae about 10 m which contains abundant pyrite crystals and fossilized fish bones both the zhuonai lake and lunpori oil shale contain high values of total organic matter toc s2 and hydrogen index hi indicating the oil shales have good oil source rock potential tmax values show an immature stage of organic matter for the zhuonai lake oil shale and thermally marginally mature for the lunpori oil shale because of difference in their burial history lunpori oil shale shows the characteristics of amorphous organic matter aom dominance odd over even predominance maximum n alkanes peak at nc25 or nc23 higher proportion of c29 sterane light 13 corg values 30 0 to 27 4 high concentrations of phytane pr ph ratio ranging from 0 02 to 0 18 high values of gammacerane index up to 25 26 and presence of carotane which are consistent with a reducing stratified and hypersaline palaeo lake with main contribution of algae and bacteria to the organic matter om oil shale samples from the lower and upper part of the zhuonai lake section are characterized by low h c ratios and high o c ratios amorphous humic om and vitrinite dominance odd over even predominance with long chain n alkanes dominance heavy organic carbon isotope and c29nc27 sterane distribution in agreement with a main contribution of land plant the heavy organic carbon isotope suggests the expanding of c4 land plant during the early miocene while the most samples show characteristics of aom dominance maximum peak at nc29 or nc31 and high c27 sterane concentration consistent with a main contribution from algae to the om the pr ph ratio cannot be applied as a measure for redox conditions in the section because of maturity effects biomarker analysis indicates that the salinity during the deposition of the zhuonai lake oil shale was not enhanced the oligocene lunpori oil shale and the early miocene zhuonai lake oil shale recorded the variation of palaeolimnological water chemistry the development history of the palaeo lakes from the oligocene saline to the early miocene fresh water reflects the variation of palaeoclimate from dry to humid in the central tibetan plateau

hydrocarbon generation potential and miocene pliocene paleoenvironments of the kangal basin central anatolia turkey abstract this study deals with the organic geochemical characteristics hydrocarbon generative potential and miocene pliocene paleoenvironments of the kangal coal district which developed in a limnic depositional environment and contains the hamal etyemez and kalburcayiri coal fields in the southern part of the sivas basin central anatolia around kalburcayiri the average thickness of each of the two coal seams approximately 10 m are currently being exploited based on open cast methods the coal from which is used by the nearby lignite fired kangal power station an attempt was made to elucidate depositional conditions through proximate and ultimate analyses coal petrography and the geochemical characteristics of the kangal coals these coals have a huminite reflectance value of rmax 0 40 accordingly from the standpoint of coal rank this is a dull brown coal of the subbituminous c type huminite is the most widespread maceral type while gelinites are the most often encountered macerals relative to liptinites the proportion of inertinites is high on the basis of maceral composition the depositional environment of the kangal coals was determined to be either a forest swamp or a lake bottom the distributions of the c27 and c28 c29 steranes for all these coal samples are very similar c29 c27 c28 tricyclic terpanes have low concentrations in all samples of the kangal coals and are dominated by low molecular weight compounds c20 c24 with a maximum at c23 total organic carbon toc wt values of the kalburcayiri samples are 4 64 30 64 wt in the hamal samples 0 83 2 53 wt and in the etyemez samples 8 91 10 39 wt on the basis of tmax values the samples are in the immature early mature stage according to rock eval pyrolysis data the coals have hydrocarbon source rock potential but the coaly shales and other organic matter rich levels have no hydrocarbon source rock potential the high inertinite levels and high vitrinite inertinite ratios suggest that the kangal coals have more potential for gas generation than oil

geochemical and palynological investigation of the shengli river marine oil shale china implications for paleoenvironment and paleoclimate abstract the shengli river oil shale located in the north qiangtang depression northern tibet plateau represents a potential large marine oil shale resource in china a geochemical and palynological investigation of the oil shale was performed to reconstruct paleoenvironment and paleoclimate during deposition the total organic carbon toc contents 15 05 20 34 and s 2 values 103 27 129 12 mg hc mg rock of oil shale samples are high and the organic matter consists mainly of type ii kerogen the thermal maturity assessed from pi 0 033 0 036 and t max 433 436 shows an immature to early mature stage of the organic matter analyzed oil shale samples from the shengli river area are characterized by a dominance of low carbon number molecular compositions with high c 21 c 21 2 10 2 83 low pr ph 0 63 0 75 and high concentrations of c 27 sterane and homohopanes c 31 c 35 indicating reducing environments highly saline conditions and a prevalent contribution of algae to organic matter accumulation the analyzed oil shale samples have an uncommonly heavy c isotopic composition ranging in 13 c values of bulk organic matter from 20 79 to 21 78 the enrichment in 13 c is mainly attributed to the high productivity of algae rather than solely the result of hypersalinity composition of palynofloras from oil shale samples suggests that the climate of the qiangtang basin region during the deposition of oil shales was warm and humid or sub humid

geochemical application of sterane and triterpane biomarkers to a description of oils from the taranaki basin in new zealand abstract the distributions of sterane and terpane biomarkers in a suite of 25 oils from onshore and offshore regions of the taranaki basin of new zealand have been determined by gc ms features of these distributions include the presence of relatively high concentrations of a number of c 24 tetracyclic terpanes the virtual absence of tricyclic terpanes a predominance of c 29 normal iso and dia steranes and the presence of a number of non hopanoid triterpanes in one member of the suite urenui 18 h oleanane is the most abundant component m z 191 ion chromatogram of the terpane class of biomarkers based upon the distributions of 18 h oleanane the mckee and moturoa families of oils can be delineated these terpane distributions are qualitatively similar to those encountered in crude oils from a number of far eastern basins and from the handil field of the mahakam delta indonesia the taranaki oils are of approximately the same thermal maturity maturity parameters calculated from the distributions of c 29 steranes and of 17s h 21 h and 17 h 21s h hopanes confirm recent findings of incomplete nuclear isomerisation in oils derived from tertiary sediments an attempt has been made to correlate the mckee 1 and maui 4 crude oils with potential source rocks from depths of 3708 m and 3825 m respectively the rocks studied have attained insufficient maturity to have been the sources of these oils

release of kerogen bound hopanoids by hydropyrolysis hydropyrolysis was used to determine the concentrations of kerogen bound hopanoid hydro carbons the samples characterized were a recent sediment priest pot english lake district and three source rock kerogens green river shale draupne shale and jet rock shale the hydropyroly zate of a hopanoid producing bacterium methylobacterium organophilum showed that this procedure does not overly obscure the original isomer compositions of the samples characterized although signifi cant side chain cleavage does occur which is inevitable with any pyrolysis method notable diaerences are observed between the composition of pyrolyzates and bitumen extracts for each of the source rock kerogens the overall level of hopane isomerization within the pyrolyzate is significantly lower than in the corresponding extracts this is particularly the case for the draupne sample the pyrolyzate of which contains 17b 21b hopanes though these are absent in the bitumen diaerences in isomeric com position of the pyrolyzates are in line with the isomer contents of the bitumen extracts the abundance of kerogen derived hopanes is highly variable both in terms of absolute concentration and also relative to the concentration of hopanes in the bitumen this is in part due to maturity diaerences but deposi tional environment and diagenetic conditions may also exert a control on kerogen bound hopane con centration these results show that hydropyrolysis provides valuable data on the concentration of kerogen bound hopanes whilst largely preserving their original isomeric composition 1998 elsevier science ltd all rights reserved

a stable carbon isotope and biological marker study of polish bituminous coals and carbonaceous shales abstract biological marker and carbon isotopic compositions of coals and carbonaceous shales from the upper carboniferous strata of the upper silesian uscb lower silesian lscb and lublin lcb coal basins were determined to assess depositional conditions and sources of the organic matter n alkane sterane and isoprenoid distribution and carbon isotope ratios are consistent with an origin from higher plants in some cases pristane phytane pr ph ratios of carbonaceous shales roof and floor shales are 29 stereoisomers typical but not conclusive of higher plant origin carbonaceous shales exhibit a wider range of sterane composition suggesting local significant input of algal organic matter significant amounts of benzohopanes and gammacerane are present in some coals although benzohopanes are present at least in small amounts in samples from many different environments they have been reported to occur most commonly in marine environments the present study seems to provide the first example where benzohopanes have been reported in significant amounts in terrestrial organic matter gammacerane is abundant in rocks or sediments deposited in carbonate or highly saline marine environments the finding of high gammacerane concentrations in the coals expands the depositional settings in which it has been observed and questions its utility as an independent indicator of hypersaline carbonate environments stable carbon isotope composition of coals and type iii kerogen in carbonaceous shales as well as correlation of stable carbon isotope composition of saturated and aromatic hydrocarbons in carbonaceous shales from both the uscb and the lscb indicate terrigenous origin bitumens are always co genetic with associated coals and kerogens isotopic data reveal that sofer s genetic classification of oils is not applicable to organic matter in coals

the effect of biodegradation and water washing on the occurrence of alkylphenols in crude oils abstract biodegraded oils from california and nigeria were analysed to assess the impact of biodegradation upon alkylphenol occurrence in crude oils the extent of biodegradation in the 13 californian samples ranged from very mild full n alkane distribution present to moderate complete degradation of c 15 n alkanes and significant reduction of acyclic isoprenoids corresponding to a range of n alkanes and acyclic isoprenoids stage 5 the data from the naturally degraded sample suites were compared to the results of an in vitro aerobic biodegradation experiment conducted with a north sea oil biodegradation resulted in significant reduction in total alkylphenol abundance and preferential depletion of c 3 and c 2 alkylated compounds in the nigerian and laboratory degraded samples these effects were most pronounced in oils in which the methylated naphthalenes had been biodegraded biodegradation stage 4 or 5 there was no clear relationship between alkylphenol abundance or molecular distributions and the extent of biodegradation in the californian samples although alkylphenol distributions in the biodegraded samples were generally dominated by the c 3 compounds simple oil water partition calculations showed that these distributions were consistent with the effects of water washing

circulation near axial seamount year long moored current measurements from 1987 to 1988 on the saddle 1860 m between axial volcano and brown bear seamount show an oscillating flow with a broadband frequency centered at about 4 days and a long term average flow of about 4 cm s southward the measurements at sill depth also suggest a possible alternating exchange of water north and south of the cobb eickelberg seamount chain with warmer water 0 05 c coming from the north however measurements near the top of the volcano at about 1400 m show a weaker but northward mean flow and the 4 day oscillation barely exists conductivity temperature and depth ctd observations on the east side of the volcano infer possible intensification of southward flow adjacent to the juan de fuca ridge similar to that found with combined ctd and current meter observations about 100 km to the south southward flow is hypothesized along the entire east side of the ridge on the west side the axial brown bear saddle may be near a convergence zone between southward and northward currents which then flow westward the highly energetic environment on the saddle suggests other gaps in the ridge and seamount chains may be important in determining the fate of the hydrothermal effluents the general oceanic flow at the top of the caldera however is more tenuous and the depth of change between these two regimes cannot be determined

a molecular isotopic study of 13c enriched organic matter in evaporitic deposits recognition of co2 limited ecosystems abstract biomarkers were analysed in a surface sediment from la trinitat saltern ponds and a miocene marl from the northern appenines both are characterised by enriched 13 c values for bulk organic matter and for biomarkers i e heavier than 20 exceptions are long chain c 22 c 34 n alkanes and c 16 c 20 fatty acids which have values typically lighter than 20 suggesting that they are not derived from aquatic organisms but from surrounding terrestrial vegetation the enriched 13 c values for biomarkers of different algae and bacteria suggest that the local microbial mat ecosystem may have been co 2 limited

relative timing of crustal plateau magmatism and tectonism at tellus regio venus crustal plateaus subcontinent sized regions of thickened crust that stand 1 4 km above surrounding low lying plains define a major physiographic province of venus thus their mode of emplacement plays a fundamental part in the evolution of the entire planet local topographic lows up to several hundred kilometers across filled with radar dark volcanic flows termed intratessera floodlava basins itbs are common within crustal plateaus itbs record abundant crustal plateau volcanism and have implications for crustal plateau emplacement and evolution we ask the fundamental question did itbs develop before during or after crustal plateau development to address this question we mapped in detail the geology a particular itb in tellus regio to determine temporal relationships between itb volcanic flows and local crustal plateau tectonism mechanical arguments and crosscutting relationships indicate that itb volcanism occurred during crustal plateau formation extending the timing relationships resolved at this basin we suggest that itb magmatism played a major role in crustal plateau genesis the geologic history discerned is consistent with the upwelling model for crustal plateau evolution in which early surface extension and volcanism would be expected in a hotspot environment conversely early widespread extension and volcanism would not be expected if crustal plateaus formed above a mantle downwelling because 1 predicted horizontal and radial convergence would obstruct early surface extension and 2 lower than normal geothermal gradients would impede rather than enhance volcanism

geochemical characteristics of tertiary saline lacustrine oils in the western qaidam basin northwest china abstract based on the systematic analyses of light hydrocarbon saturate aromatic fractions and c isotopes of over 40 oil samples along with related tertiary source rocks collected from the western qaidam basin the geochemical characteristics of the tertiary saline lacustrine oils in this region was investigated the oils are characterized by bimodal n alkane distributions with odd to even c11 c17 and even to odd c18 c28 predominance low pr ph mostly lower than 0 6 high concentration of gammacerane c35 hopane and methylated mttcs reflecting the high salinity and anoxic setting typical of a saline lacustrine depositional environment mango s k1 values in the saline oils are highly variable 0 99 1 63 and could be associated with the facies dependent parameters such as pr ph and gammacerane indexes compared with other tertiary oils the studied tertiary saline oils are marked by enhanced c28 sterane abundance 30 or more of c27 c29 homologues possibly derived from halophilic algae it is noted that the geochemical parameters of the oils in various oilfields exhibit regular spatial changes which are consistent with the depositional phase variations of the source rocks the oils have uncommon heavy c isotopic ratios 24 to 26 and a flat shape of the individual n alkane isotope profile and show isotopic characteristics similar to marine organic matter the appearance of oleanane and high 24 24 27 norcholestane ratios 0 57 0 87 in the saline oils and source rocks confirm a tertiary organic source

chemical molecular and isotopic differentiation of organic facies in the tertiary lacustrine duaringa oil shale deposit queensland australia abstract total organic matter extractable organic matter bitumen and pyrolysates released on low temperature sealed tube pyrolysis of kerogen were analysed chemically and isotopically based on bulk bitumen and biomarker parameters the sediments are immature to a depth of approx 1300 m within the terrestrial and lacustrine depositional environments of the tertiary duaringa basin various organic facies have been classified according to inorganic input and maceral abundances of organic matter derived from land plant and algal sources the latter derived mainly from pediastrum and with a varying botryococcus content the lacustrine upper lamosite is chemically and isotopically distinct from the lower lamosite due to a changing algal community relative contributions from allochthonous land plants and for the lower lamosite a slightly more saline and restricted lake environment the lower lamosite is associated with the highest concentrations of c 28 c 30 4 methylsteranes and 13 c depletion in toc in the upper lamosite there is a strong positive correlation between botryococcus content and 13 c enrichment the organically lean claystones have sources nearly identical to the lamosites but the organic matter is diluted due to rapid influx of siliciclastics the terrestrial facies the cannel coal and carbonaceous shales are mainly distinguished from the lacustrine facies by higher relative proportions of c 29 steranes c 30 4 methylsteranes and 13 c values for the pyrolysed hydrocarbons intermediate between the two lamosite facies the carbonaceous oil shale has a composite geochemical signature intermediate between the two end members lamosite and cannel coal oleanane and ring a degraded triterpanes derived from lupane arborane and oleanane skeletons are distributed throughout all organic facies representing both autochthonous and allochthonous higher plant inputs higher concentrations of oleanane and des a lupane are associated with the terrestrial facies hopanes dominate over steranes in all organic facies and their concentration ranges are independent of facies for the lamosites the aliphatic biopolymer algaenan is implicated as the dominant source for n alkanes from analysis of their yields homologue abundances and individual 13 c values in the terrestrial facies resinites are paraffinic and are a major source for the n alkanes released on pyrolysis compound specific analysis of extractable and pyrolysate hydrocarbons allowed deconvolution of different source inputs to free lipids and kerogen for the lamosites low molecular weight n alkanes in the bitumen are derived mainly from a pediastrum source while botryococcus is associated with waxy n alkanes however the situation is reversed in the kerogen pediastrum algeanan has a longer average alkyl chain length than botryococcus algaenan the magnitude of the isotopic differences between single n alkanes released at different temperatures is useful in determining multiplicity of sources

biological marker compounds as indicators of the depositions history of the maoming oil shale abstract the eocene maoming oil shale from guangdong province occurs as a laterally uniform stratigraphic section typically 20 25 m thick from which the aliphatic hydrocarbon constituents of six representative samples were investigated using gc and c gc ms the sediments evaluated included the basal lignite a vitrinite lens from the overlying claystone and four intervals from the massive oil shale bed as expected the lignite and vitrinite differ markedly from the oil shales the lignite is dominated by bacterial hopanoids and components of higher plant origin including c 29 steroids and triterpenoids such as oleanenes visually the oil shale samples show corroded and degraded phytoclasts spores wispy particles of fluorescent organic material attributable to dinoflagellates and especially in the uppermost sample colonial algal bodies the distributions of biological markers in the oil shales show many features in common notably a dominance of dinoflagellate derived 4 methylsteroids and a significant proportion of higher plant derived n alkanes with marked odd over even carbon number predominance overall they exhibit several features that resemble characteristics of the messel shale the hydrocarbons of the lowest shale horizon suggest that there may have been a gradual transition between deposition of the original peat and the subsequent oil shales the aliphatic hydrocarbons of the uppermost shale are dominated by a number of c 31 and c 33 botryococcane homologues and other unusual branched alkanes possibly derived from green algae all of the samples are immature overall molecular and microscopic examination of the stratigraphic succession of the maoming oil shale suggests a shallow lacustrine environment within which peats were deposited this lake subsequently deepened to support abundant algal populations especially dinoflagellates culminating in a dominance of botryococcoid algae

mineralogy and organic petrology of oil shales in the sangkarewang formation ombilin basin west sumatra indonesia abstract the ombilin basin is filled by late eocene to early oligocene marginal fan deposits brani formation and lacustrine shales sangkarewang formation unconformably overlain by a late oligocene to early miocene fluvial sequence sawahlunto and sawahtambang formations and capped by an early to mid miocene marine sequence ombilin formation significant oil shale deposits occur in the sangkarewang formation intercalated with thin laminated greenish grey calcareous sandstones x ray diffraction shows that the sediments consist mainly of quartz feldspar carbonates and a range of clay minerals together in some cases with minor proportions of sulphides evaporites and zeolites feldspar and non kaolinite clay minerals decrease up the sequence relative to kaolinite suggesting a changing sediment source as the basin was filled calcite thought to be mainly of authigenic origin is also more abundant in the middle and upper parts of the sequence the organic matter in the oil shales of the sequence is dominated by liptinite macerals particularly alginite mainly lamalginite and sporinite cutinite also occurs in some samples along with resinite and traces of bituminite the dominance of lamalginite in the liptinite components suggests that the material can be described as a lamosite samples from the sangkarewang formation have vitrinite reflectance values ranging between 0 37 and 0 55 these are markedly lower than the vitrinite reflectance for coal from the overlying sawahlunto formation 0 68 possibly due to suppression associated with the abundant liptinite in the oil shales fischer assay data on outcrop samples indicate that the oil yield is related to the organic carbon content correlations with xrd data show that with one exception the oil yield and organic carbon can also be correlated directly to the abundance of carbonate calcite and inversely to the abundance of quartz plus feldspar this suggests that the abundance of algal material in the lake sediments was preferentially associated with carbonate deposition high yields of oil are noted in some samples as a percentage of the organic carbon content this may indicate that partial generation of hydrocarbons from the material has already taken place in association with thermal maturation of the sangkarewang succession

thermal maturity and organic composition of pennsylvanian coals and carbonaceous shales north central texas implications for coalbed gas potential thermal maturity was determined for about 120 core cuttings and outcrop samples to investigate the potential for coalbed gas resources in pennsylvanian strata of north central texas shallow 600 m 2000 ft coal and carbonaceous shale cuttings samples from the middle upper pennsylvanian strawn canyon and cisco groups in archer and young counties on the eastern shelf of the midland basin northwest and downdip from the outcrop yielded mean random vitrinite reflectance r o values between about 0 4 and 0 8 this range of r o values indicates rank from subbituminous c to high volatile a bituminous in the shallow subsurface which may be sufficient for early thermogenic gas generation near surface 100 m 300 ft core and outcrop samples of coal from areas of historical underground coal mining in the region yielded similar r o values of 0 5 to 0 8 carbonaceous shale core samples of lower pennsylvanian strata lower atoka group from two deeper wells samples from 1650 m 5400 ft in jack and western wise counties in the western part of the fort worth basin yielded higher r o values of about 1 0 pyrolysis and petrographic data for the lower atoka samples indicate mixed type ii type iii organic matter suggesting generated hydrocarbons may be both gas and oil prone in all other samples organic material is dominated by type iii organic matter vitrinite indicating that generated hydrocarbons should be gas prone individual coal beds are thin at outcrop 1 m 3 3 ft laterally discontinuous and moderately high in ash yield and sulfur content a possible analog for coalbed gas potential in the pennsylvanian section of north central texas occurs on the northeast oklahoma shelf and in the cherokee basin of southeastern kansas where contemporaneous gas producing coal beds are similar in thickness quality and rank

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