recognition of 18β h oleanane in several crudes and tertiary upper cretaceous sediments definition of a new maturity parameter abstract ekweozor et al chem geol 27 11 28 and 29 37 first discovered an unknown compound with a gc retention time very close to that of the 18 h olenane peak in oils and tertiary sediments of the nigerian delta this compound was called j several authors wang et al advances in organic geochemistry 1981 pp 108 113 wiley chichester 1983 schoelle et al ibid pp 156 163 reported the occurrence of 18 h oleanane without underlying the presence of j because of their coelution in this study the presence of j has been confirmed in more than 150 rock extracts and 19 oils from different countries and is identified as the 18 h oleanane by comparison to retention time and mass spectrum and by its coelution with an authentic standard apart from tertiary sediments the 18 h and 18 h oleananes have also been found in upper cretaceous sediments which extends the occurrence of these compounds back in age a maturity correlation has been found between the relative concentration of 18 h oleanane and 18 h oleanane in fact an increase in the 18 h 18 h oleanane ratio has been observed with increasing depth in several wells the 18 h 18 h oleanane ratio has been correlated with other classical maturity parameters i e ts tm ro and tmax

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

alkyldibenzofurans in terrestrial rocks influence of organic facies and maturation abstract dibenzofuran dbf dibenzothiophene dbt and phenanthrene phe have been determined along with their methyl derivatives mdbfs mdbts mps in coals carbonaceous shales and mudstones of lower cretaceous to upper carboniferous ages from the elmworth gas field canada and from the sakoa madagascar and ruhr coal germany basins the samples contained mainly terrestrial organic matter with thermal maturities in the 0 7 1 9 mean vitrinite reflectance rr range the pronounced predominance of mdbfs over mdbts in the sakoa samples is typical of plant debris deposited in lacustrine swamp environments onset of intense mdbf generation occurs at fairly low rank 0 77 rr as indicated by elevated concentrations of 50 120 g mdbfs g total organic carbon toc influences of lithology organic matter type and maturity on distributions of the target compounds were extracted from the molecular concentration data by multivariate statistical methods such as principal components analysis pca and fuzzy c means cluster analysis with nonlinear mapping nlm a specific source effect on 1 mdbt concentrations suggests that lichens contributed to the senescent coal forming forest in the sakoa coal basin alkyldibenzofurans hence are potential lichen biomarkers mdbfs can be used as maturity indicators only beyond 1 0 rr where ruhr coals displayed a distinct increase in the 1 4 mdbf ratio

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

spatial variability in biogenic gas accumulations in peat soils is revealed by ground penetrating radar gpr 1 we performed surface and borehole ground penetrating radar gpr tests together with moisture probe measurements and direct gas sampling to detect areas of biogenic gas accumulation in a northern peatland the main findings are 1 shadow zones signal scattering observed in surface gpr correlate with areas of elevated ch4 and co2 concentration 2 high velocities in zero offset profiles and lower water content inferred from moisture probes correlate with surface gpr shadow zones 3 zero offset profiles depict depth variable gas accumulation from 0 10 by volume 4 strong reflectors may represent confining layers restricting upward gas migration our results have implications for defining the spatial distribution volume and movement of biogenic gas in peatlands at multiple scales

gas bubble transport and emissions for shallow peat from a northern peatland the role of pressure changes and peat structure gas bubbles are an important pathway for methane release from peatlands the mechanisms controlling gas bubble transport and emissions in peat remain uncertain the effects of hydrostatic pressure and peat structure on the dynamics of gas bubbles in shallow peat were therefore tested in laboratory experiments a peat monolith was retrieved from a raised bog and maintained in a saturated state three distinct layers were identified from noninvasive permittivity measurements supported by soil physical properties porosity bulk density phase i of the experiment involved monitoring for the accumulation of gas bubbles under steady pressure and temperature conditions the data showed evidence for gas bubbles being impeded by a shallow semiconfining layer at depths between 10 and 15 cm visible gas bubbles observed on the side of the sample box were recorded over time to estimate changes in the vertical distribution of volumetric gas content porosity estimates derived using the complex refraction index model crim suggest that gas bubbles enlarge the pore space when the exerted pressure is high enough phase ii involved triggering release of trapped bubbles by repeatedly increasing and decreasing hydrostatic pressure in an oversaturated condition comparison of changes in pressure head and methane density in the head space confirmed that the increasing buoyancy force during drops in pressure is more important for triggering ebullition than increasing mobility during increases in pressure our findings demonstrate the importance of changes in hydrostatic pressure on bubble size and variations in resistance of the peat fabric in regulating methane releases from peatlands

tracing early charged oils and exploration directions for the wenchang a sag western pearl river mouth basin offshore south china sea the wenchang a sag is the largest petroleum producing sub depression in the western pearl river mouth basin offshore south china sea the eocene wenchang formation and the early oligocene enping formation are the two major source rocks in the sag the oil discoveries in this region mainly originated from the enping fm how to objectively estimate the petroleum potential of the wenchang fm and trace the wenchang oils has long been the focus of research and exploration in this region in this paper inclusion oils obtained from reservoir sandstones as well as typical reservoir oils and potential source rocks were investigated by systematic geochemical methods oil oil and oil source rock correlations indicate that inclusion oils in the central and marginal areas of the wenchang a sag had similar geochemical characteristics and mainly originated from the wenchang source rocks the reservoir oils in the central area are derived mainly from the enping source rocks while in the marginal areas they have mixed characteristics of both the enping and wenchang formations combining the tectonic sedimentary evolution and petroleum generation histories it is concluded that the two source rocks in the wenchang a sag have generated oils but in the central areas the main stage of oil generation of the wenchang fm was much earlier than the formation time of the traps resulting in the dissipation of most of the early generated wenchang sourced oils in the marginal areas the main stage of oil generation of the wenchang fm was later and the wenchang oils not only could be captured as fluid inclusions in the reservoir quartz grains but also migrated and accumulated into oil pools in which they mixed with the enping sourced oils the early lithological and structural traps in the central and marginal areas of the wenchang a sag especially in the northern part of the shenhu uplift are the most prospective areas for further exploration of the sag

the diagenetic fate of taraxer 14 ene and oleanene isomers abstract the extractable organic matter in holocene to early miocene deep sea sediments from site 645 odp leg 105 in baffin bay contains almost exclusively biological markers of terrigenous origin pentacyclic triterpenoids of the ursene and amyrin oleanene type often occur as the most abundant compounds in the aliphatic hydrocarbon ketone and alcohol fractions of the sediment extract a specific diagenetic reaction involves the conversion of taraxer 14 ene into olean 12 ene in the upper 700 metres of the sedimentary sequence the taraxerene to oleanene conversion is complete before the onset of isomerisation of diasterenes at c 20 in the sediment as well as in laboratory simulation experiments olean 12 ene further isomerises to olean 13 18 ene and olean 18 ene the latter of which may be the direct precursor of 18 h and 18 h oleanane found in sediments containing more mature organic matter and in crude oils the subsurface interconversion of these triterpenoid skeletons indicate that oleanane does not necessarily start life as an oleanoid

identification of bicadinanes in jurassic organic matter from the eromanga basin australia cis cis trans and trans trans trans bicadinanes were identified in a jurassic crude oil and two jurassic rocks from the eromanga basin australia after the branched and cyclic alkane fractions had been enriched in bicadinanes using ultrastable y molecular sieves these biomarkers have previously been reported only from angiosperms and their occurrence in jurassic samples may indicate the early evolution of flowering plants in this basin

novel c26 tetracyclic degraded bicadinanes in oil sands from the haitoubei maichen sag of the beibuwan basin south china sea abstract three c 26 tetracyclic terpanes were detected in the saturated hydrocarbon fractions of oil sand samples especially rich in bicadinanes w t and r from the oligocene huizhou formation in the xw 1 well in the haitoubei maichen sag of the beibuwan basin their mass spectra show molecular ions of the three tetracyclic terpanes at m z 358 and their key fragment ions at m z 343 m 15 and m z 315 due to loss of an isopropyl group these characteristics are very similar to that of c 30 cis cis trans w and trans trans trans t bicadinanes in addition the relative abundances of the c 26 tetracyclic terpanes show an excellent positive correlation with the c 30 bicadinanes w and t in 27 oil sand samples therefore the three c 26 tetracyclic terpanes are tentatively identified as degraded bicadinanes which like bicadinanes may indicate input from dammar resins and can be used to discriminate the origin of crude oils

configurational isomerization in sedimentary bicyclic alkanes the soluble organic matter and pyrolysate from a sample suit of triassic sediments have been analyzed by gc ms techniques for c 8 epimers of drimane and homodrimane the relative abundance of epimers is maturity dependent compounds with the 8 h configuration being dominant in more mature samples these changes have been attributed to isomerization reactions which result in apparent equilibration of epimers before the onset of significant hydrocarbon generation

methane emissions from wetlands in the zone of discontinuous permafrost fort simpson northwest territories canada we examined the influence of water table position temperature vegetation and ch 4 storage on ch 4 flux at 22 wetland sites located in the zone of discontinuous permafrost near fort simpson northwest territories sites ranged from frozen peat plateaux and palsas with collapse scars to fens and bogs and ponds mean summer ch4 emissions ranged from 1 3 to 255 mg m 2 d 1 and the variation among sites was best explained by mean water table position r 2 0 62 n 19 large ch 4 fluxes 30 mg m 2 d 1 and high water tables occurred in ponds and graminoid sites whereas small fluxes 30 mg m 2 d 1 and low water tables occur in shrub and woody sites these relationships were upheld across several northern boreal regions based on water table depth and broad ecological criteria ch4 turnover times were generated by comparing surficial fluxes and storage within the saturated portion of the peat profile graminoid sites had ch 4 turnover times from 1 to 4 days whereas shrub or woody sites had longer turnover times ranging from weeks to years we estimated an overall flux of 18 mg m 2 d 1 for the landscape around fort simpson this ch 4 flux may increase with the onset of global warming owing to the fragility of permafrost resulting in the formation of collapse scars with high ch 4 emission rates

triterpane and sterane biomarkers in the ya13 1 condensates from qiongdongnan basin south china sea triterpanes and steranes in condensates from the ya13 1 gas field qiongdongnan basin were monitored the ya13 1 condensates have unusual biomarker distributions dominated by terpanes and steranes derived from higher plants anomalously abundant 1 got oleanane and remarkably abundant bicadinanes are present in the ya13 1 condensates whereas the 17alpha hopane contents are extremely low taraxastane and significantly abundant 17alpha diahopanes occur in the condensates in addition a number of unknown c 29 and c 30 pentacyclic triterpanes including previously unreported compounds were detected in the condensates some of which are significantly abundant the unknown compounds may be terrestrial biomarkers c 29 homologues are relatively predominant among the regular and rearranged steranes the diasterane concentrations are markedly higher than those of regular steranes the maturity of the ya13 1 condensates is relatively high at the peak to late oil generation stage corresponding to 0 85 1 10 ro based on sterane and terpane and including bicadinane maturity parameters i e t t 1 r and 2t r bicadinane ratios the above maturity assessment result is different from that based on diamondoid maturity parameters ro 1 60 1 70 org geochem 25 1996 179 which can be explained by a contribution of hydrocarbons from two sources at different depths the ya13 1 condensates were probably generated from the yacheng and lingshui coal bearing source rocks buried both in the qiongdongnan basin 3400 5000 m and in the yinggehai basin 5000 m the possible contribution of lower maturity hydrocarbons from the yacheng and lingshui formations 3400 4100 m in the qiongdongnan basin to the ya13 1 gases and condensates should not be neglected c 2003 elsevier science b v all rights reserved

sterane isomerisation and moretane hopane ratios in crude oils derived from tertiary source rocks the extent of sterane isomerisation reactions and the moretane hopane ratios of 234 crude oils taken world wide from a wide variety of source rocks of differing geological ages have been measured this data indicates that in 78 crude oils derived from tertiary source rocks sterane isomerisation reactions as determined by the 20s 20s 20r ration of the c29 5 h 14 h 17 h normal steranes and the c29 iso iso normal ratio iso 5 h 14 h 17 h are mainly incomplete and sometimes considerably so in addition the same crude oils have 17 h 21 h moretane 17 h 21 h hopane ratios which are significantly greater predominantly in the range 0 10 0 30 than those of crude oils derived from older mature source rocks mainly less than 0 1 this data for crude oils lends support to the hypothesis proposed by mackenzie and mckenzie 1983 for source rock extracts that the time temperature constraints of sterane isomerisation reactions are such that the time available for isomerisation in tertiary sediments is generally insufficient despite generation of crude oil at relatively high temperatures an alternative hypothesis is that the incomplete sterane isomerisation of tertiary crude oils may be due to generation of these crude oils from their deltaic land plant containing source rocks under low heating conditions a third hypothesis proposes that the tertiary crude oils may have picked up the incompletely isomerised steranes from immature sediments during migration although possible in particular instances such a mechanism does not appear to be generally applicable since in that case the phenomenon would then appear to be restricted to the tertiary the higher moretane hopane ratios of the tertiary crude oils could suggest that constraints similar to those applying in sterane isomerisation also operate in the conversion of moretane to 17 h hopane

geochemistry and origins of petroleum in the neogene reservoirs of the baiyun sag pearl river mouth basin abstract a total of 25 light oils condensates 5 condensates from 2 new exploratory wells were collected from the baiyun sag in the pearl river mouth basin prmb in the south china sea and investigated to establish their origins and sources three oil families were identified among samples following analysis of various geochemical parameters using biomarkers stable carbon isotope compositions and hierarchical cluster analysis hca family i oils distributed in the northern structural belts are characterized by significantly high pristane to phytane pr ph ratios 4 77 7 93 moderate oleanane to c30 hopane ol c30h ratios 0 18 0 97 and raised bicadinane t c30h t c30h ratios 1 67 7 67 family ii oils are distributed along the eastern flank of the main sub sag towards the northeastern tectonic zones and have relatively high pr ph ratios 3 14 4 68 elevated ol c30h values 0 73 2 29 and moderate t c30h values 1 64 4 52 the geochemical characteristics of the oils suggest that oils of both family i and family ii are of terrestrial origin but from two entirely independent sources oils of family iii a newly discovered oil group have relatively lower pr ph ratios 0 89 1 99 moderate ol c30h values 0 13 0 82 and lower t c30h values 0 34 1 61 indicating a reduced contribution of higher plant organic matter in related source rocks family iii oils are consistent in geochemical characteristics with shallow lacustrine source rocks and their related oils discovered in the zhu i and iii depressions of the prmb suggesting that they are likely to be derived from source rocks deposited in a shallow lacustrine environment during the eocene wenchang enping period the oils of family iii mainly occur in the southwest flank of the baiyun sag which implies that this is the preferred direction for migration of lacustrine oils the discovery of lacustrine oil demonstrates that the baiyun sag possesses enormous exploration potential in lacustrine oils and that this may become the next favored petroleum exploration target

the origin and distribution of crude oil in zhu iii sub basin pearl river mouth basin china abstract the origin of thirteen major oil fields in zhu iii sub basin pearl river mouth basin was studied by using the results of rock eval pyrolysis on 340 samples and biomarker analysis on 18 source rock samples and 33 oil samples the two possible source rock intervals have different biomarker assemblages and were deposited in different environments the eocene wenchang formation e2w 49 5 35 ma is characterized by high hopane sterane ratio 37 84 high 4 methyl sterane index 0 28 1 06 low gammacerane index 0 10 high bicadinane c30 hopane up to 73 62 but low hopane sterane ratio

methane flux from drained northern peatlands effect of a persistent water table lowering on flux measurements of ch4 flux from drained and undrained sites in three northern ontario peatlands a treed fen a forested bog and a treed bog were made from the beginning of may to the end of october 1991 in the drained portions the water table had been lowered between 0 1 and 0 5 m compared to the water table of the undrained portion of the peatlands the mean seasonal ch4 flux from the undrained portions of three peatlands was small ranging from 0 to 8 mg m 2d 1 but similar to the ch4 flux from other treed and forested northern peatlands the mean seasonal ch4 flux from the drained portion of the peatlands was either near zero or slightly negative i e uptake fluxes ranged from 0 1 to 0 4 mg m 2 d 1 profiles of ch4 in the air filled pores in the unsaturated zone and the water filled pores of the saturated zone of the peat at the undrained sites showed that all the ch4 produced at depth was consumed within 0 2 m of the water table and that atmospheric ch4 was consumed in the upper 0 15 m of the peatland on the basis of laboratory incubations of peat slurries to determine ch4 production and consumption potentials the lowering of the water table eliminated the near surface zone of ch4 production that existed in the undrained peatland however drainage did not alter significantly the potential for ch4 oxidation between the water table and peatland surface but increased the thickness of the layer over which ch4 oxidation could take place these changes occurred with a drop in the mean summer water table of only 0 1 m from 0 2 to 0 3 m suggesting that only a small negative change in soil moisture would be required to significantly reduce ch4 flux from northern peatlands

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

cyclic terpenoids of contemporary resinous plant detritus and of fossil woods ambers and coals abstract cyclic terpenoids present in the solvent extractable material of fossil woods ambers and brown coals have been analyzed the sample series chosen consisted of wood remains preserved in holocene to jurassic sediments and a set of of ambers from the philippines copalite israel canada and dominican republic the brown coals selected were from the fortuna garsdorf mine and miocene formations on fiji the fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons and aromatized species were present at high concentrations with a major amount of two ring aromatic compounds tricyclic diterpenoids were the predominant compounds in the ambers aromatized derivatives were the major components consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons the saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon c1 c2 etc substituents kaurane and phyllocladane isomers were present in only minor amounts bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples but only traces of sesterterpenoids and triterpenoid derivatives were found the brown coal extracts were composed of major amounts of one and two ring aromatized terpenoids with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers this was especially noticeable for the german coal where the triterpenoids were predominant open c ring aromatized structures were also present in this coal steroid compounds were not detectable but some hopanes were found as minor components in the german brown coal an overview of the skeletal structure classes identified in each sample as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper it can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis constituting a general pathway for all terpenoids

possible algal origin of long chain odd n alkanes in immature sediments as revealed by distributions and carbon isotope ratios a pliocene oil shale pula hungary a c3 plant triticum aestivum and a c4 plant zea mays were compared using isotopic composition of bulk organic matter along with distributions and individual carbon isotope ratios of n alkanes from organic extracts the microalga botryococcus braunii a race was thus shown to be the main source of the predominant 27 29 and 31 n alkanes of pula sediment therefore the dominance of odd carbon numbered n alkanes in the range c25 35 in extracts from immature sediments shall not be systematically assigned to higher plant contribution but algal input is also possible in fact the long chain n alkanes with an odd predominance previously observed in extracts of various immature sediments are likely to be derived at least partially from algae

new insights into the origin of perylene in geological samples abstract the origin of the polycyclic aromatic hydrocarbon pah perylene in sediments and petroleum has been a matter of continued debate reported to occur in phanerozoic organic matter om fossil crinoids and tropical termite mounds its mechanism of formation remains unclear while a combustion source can be excluded structural similarities to perylene quinone like components present in e g fungi plants crinoids and insects potentially suggest a product precursor relationship here we report perylene concentrations 13c 12c and d h ratios from a holocene sediment profile from the qingpu trench yangtze delta region china perylene concentrations differ from those of pyrogenic pahs and rise to prominence in a stratigraphic interval that was dominated by woody vegetation as determined by palynology including fungal spores in this zone perylene concentrations exhibit an inverse relationship to the lignin marker guaiacol d h ratios between 284 and 317 similar to the methoxy groups in lignin as well as co variation with spores from wood degrading fungi 13c 12c of perylene differs from that of land plant wax alkanes and falls in the fractionation range expected for saprophytic fungi that utilise lignin which is isotopically lighter than cellulose and whole wood during progressive lignin degradation the relative carbon isotopic ratio of the perylene decreases we therefore hypothesise a relationship of perylene to the activity of wood degrading fungi to support our hypothesis we analysed a wide range of phanerozoic sediments and oils and found perylene to generally be present in subordinate amounts before the evolutionary rise of vascular plants and to be generally absent from marine sourced oils few exceptions being attributed perhaps to a contribution of marine and or terrestrial derived fungi anoxia especially under marine conditions and or contamination of core material by fungi a series of low molecular weight aromatic quinones bearing the perylene backbone were detected in devonian and cretaceous sediments potentially representing precursor components to perylene

occurrence of polycadinene in fossil and recent resins abstract dammars produced by dipterocarpaceae growing in southeast asia are partly composed of a macromolecule with a polycadinene structure this polymer is the precursor of many specific compounds encountered in crude oils and sediment extracts from south asia until recently there was no evidence for a more widespread geographical occurrence of this resinous polymer using different pyrolysis methods it is shown that the polymers present in a resinite from utah usa and in resins contained in resin canals of eocene fossil fruits from germany and england are also polycadinenes the fossil fruits were undoubtedly produced by ancient representatives of mastixioid cornaceae a group of plants which was widespread in the tertiary of europe and north america and which is not related to dipterocarpaceae these findings extend the known occurrence and origin of the sesquiterpenoid type resin polymer it is to be expected that catagenetic products of these resin polymers should be present in oils coals and sediment extracts from areas outside southeast asia

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

lacustrine organic facies a biomarker study using multivariate statistical analysis abstract four distinct depositional settings in the devonian orcadian basin of scotland have been characterised by their minerology and organic geochemistry with the help of multivariate statistical analysis the data visualise the organic matter source input the depositional environment and the level of thermal maturity principal component analysis proved invaluable for extracting information from a data set composed of a large number of parameters the thermal maturity of the majority of the samples lies within a restricted range in the oil window and biomarker composition reflects predominantly organic input and depositional environment basin margin deposits are clearly differentiated from deeper water central lake deposits salinity and anoxicity variations are seen within the latter type of deposits

polycyclic aromatic hydrocarbons pahs in late eocene to early pleistocene mudstones of the sylhet succession ne bengal basin bangladesh implications for source and paleoclimate conditions during himalayan uplift abstract distribution and possible sources of polycyclic aromatic hydrocarbons pahs have been investigated in 23 late eocene to early pleistocene mudstones from the sylhet succession of the northeastern bengal basin bangladesh paleoclimatic conditions in the southern himalaya region throughout the himalayan uplift were reconstructed based on combustion derived pahs and aromatic land plant derived biomarkers phenanthrene fluoranthene fla pyrene py benz a anthracene baan chrysene triphenylene chry tpn benzofluoranthenes bflas benzo e pyrene bepy benzo a pyrene bapy perylene pery indeno 1 2 3 cd pyrene inpy benzo ghi perylene bghip coronene cor and retene ret were the identified pahs fla fla py ratios 0 5 and inpy inpy bghip 0 2 from almost all sylhet samples suggest occurrence of natural wildfires low contents of baan and bapy indicate decomposition by long exposure to sunlight before sedimentation or early diagenetic weathering increased cor inpy and bghip contents suggest occurrence of larger high temperature wildfires correlation coefficients of the pahs and p values for statistical hypothesis testing showed that the positive and negative correlations within the pahs may be indicative of high or low temperatures in wildfires fungi derived pery showed negative correlations with py r 0 67 p 4 6 10 4 and fla r 0 56 p 5 0 10 3 but not with cor bflas inpy and bghip based on the correlation coefficients for all pahs and their p values five statistical groups py fla cor bflas inpy bghip baan chry tpn bapy pery and ret were recognized these groups are probably correlated with origins and depositional processes according to the results the sylhet succession was deposited in three differing paleoclimatic regimes 1 first phase late eocene to early miocene early to middle stage of himalayan uplift high contents of combustion derived pahs fla py and bepy significant gymnosperm derived ret and low pery abundances in the jaintia and barail groups indicate arid climatic conditions although wildfires could often occur 5 or 6 ring combustion pahs cor inpy and bghip contents are low suggesting that the wildfires were relatively low temperature 2 second phase middle to late miocene middle to late stage of himalayan uplift combustion derived pahs and fungi derived pery were dominant in the surma group the climate was arid to humid and seasonal with a dry season giving conditions suitable for combustion abundant fla bflas bepy cor inpy and bghip imply high temperatures in large wildfires however frequency of the wildfires decreased because of wet climate 3 third phase late miocene to pleistocene late stage of himalayan uplift moderate to high pery contents and low fla py and bepy abundances in the tipam and dupitila groups indicate establishment of more humid climate inpy bghip cor bflas and bapy were predominant intensified humid and seasonal climate arising from the himalayan monsoon decreased the incidence and frequency of general wildfires but increased the ratio of large to small wildfires

oleanane or lupane reappraisal of the presence of oleanane in cretaceous tertiary oils and sediments nonpolar gc columns are normally used for gc ms analysis of saturate fractions from crude oils under these conditions lupane coelutes with oleananes and some minor c30 compounds of non terrigenous origin having lupane like mass spectra because any peak eluting fractionally earlier than 17 21 h hopane in the m z 191 mass chromatogram is routinely assigned to oleanane the presence of lupane may sometimes have been overlooked lupane and oleananes are easily separated using reverse phase hplc triterpane concentrates from 10 crude oils known to contain oleananes were hplc separated lupane was unambiguously identified in six of the oils by full scan gc ms analysis of fractions having the hplc retention time of authentic lupane gc separation of lupane and oleananes is possible using polar gc columns having a polyethylene glycol stationary phase organic geochemistry 23 1995 21 allowing estimation of the lupane lupane oleanane ratio high ratios were measured in the marraat oil west greenland 0 8 and the amauligak oil from the beaufort mackenzie delta 0 26 the results suggest that lupane may be more frequently occurring than previously thought and that this compound is preferably associated with high latitude samples high concentrations of 28 nor and 24 28 bisnortriterpanes oleananes lupanes and taraxastanes were detected in the marraat oil

the biomarker composition of some crude oils from sumatra abstract crude oils from the north central and south sumatra basins have been analysed using gc and gc ms techniques and the biomarker compositions of the crude oils have been used to classify the samples into three types one oil from the north sumatra basin contained 3 methylhexadecane 2 methylhexadecane pristane and phytane in similar abundances regular steranes and 24 n propylcholestanes indicative of an algal contribution a series of 30 norhopanes and an absence of plant derived pentacyclic triterpanes these features have been interpreted as indicating a marine carbonate depositional setting two crude oils from the central sumatra basin are waxy crudes with abundant botryococcane pristane phytane and abundant 4 methyl 24 ethylcholestanes relative to dinosteranes these features suggest a brackish lacustrine depositional setting one light oil from the north sumatra basin and two crude oils from the south sumatra basin have abundant pristane compared with n c 17 and a high pristane phytane value the saturated polycyclic compounds are dominated by bicadinanes and other pentacyclic triterpanes of land plant origin the presence of abundant oleananes in these samples has been interpreted as evidence for deltaic near shore depositional setting these results show that crude oils from the sumatran region have source rocks with a range of depositional environments however the major oil fields are associated with lacustrine source rocks

an organic geochemical investigation of crude oils from shanganning jianghan chaidamu and zhungeer basins people s republic of china abstract eighteen oils from four different oil producing basins in china have been characterized using a variety of organic geochemical techniques the source materials for these oils were deposited under a variety of environmental conditions and this study investigates the use of geochemical parameters in differentiating the resultant oils the parameters discussed are based on relative amounts and distributions of both individual and groups of biomarkers including organosulphur compounds and the carbon isotopic composition of the aliphatic and aromatic fractions examination of the oils showed that those from the zhungeer basin thought to be derived from source rocks formed in a brackish lacustrine environment possessed high concentrations of tricyclic terpanes relative to pentacyclic hopanes and a predominance of 24 methyl and 24 ethylcholestanes c28 and c29 respectively over cholestanes c27 which were virtually absent oils believed to be derived from source rocks deposited in the saline depositional environment of the jianghan basin were characterized by a large amount of gammacerane relative to 17 21 30 homohopanes c31 22r and 22s in general those oils considered to be derived from source rocks deposited in fresh water lacustrine environments shanganning and chaidamu basins had small amounts of tricyclic terpanes relative to pentacyclic hopanes the presence of an unknown c30 pentacyclic terpane small amounts of extended hopanes c31 c35 relative to 17 21 hopane and relatively large amounts of 24 ethylcholestanes 20r and 20s relative to total stearanes it appears therefore that the distribution of biomarkers may be used to differentiate oils derived from different lacustrine environments

unusual biological marker geochemistry of oils and possible source rocks offshore beaufort mackenzie delta canada abstract tertiary oils and source rocks from the offshore beaufort mackenzie delta have been examined for their biological marker content the triterpane and sterane distributions suggest a predominant land plant contribution to the oils the oils range in maturity from extremely immature to moderately mature 18 h oleanne is a major triterpane of the oils together with probable bisnorlupanes and an excellent correlation is observed in the concentration of these components in individual oils an excellent correlation is also observed between the concentration of bisnorlupanes and oil maturity based on sterna and triterpane maturation parameters suggesting that the decrease in relative concentration of these components with increasing maturity is a result of progressive dilution by hydrocarbons generated by the cracking of kerogen only one formation in cores taken from the delta has been found to contain bisnorlupanes and were present they are the dominant hydrocarbons of the branched cyclic fraction

organic geochemical and paleoenvironmental characterization of the brown shale formation kiliran sub basin central sumatra basin indonesia abstract the central sumatra basin csb formed during the late eocene to early oligocene is the most prolific hydrocarbon basin in indonesia the brown shale formation of the pematang group is the sole known source rock for the tens of billions of barrels of oil located in the csb samples analyzed in this study were from the karbindo coal mine in the kiliran graben of the kiliran sub basin located on the western side of the csb this study incorporates advanced organic geochemical and petrographical data of samples from the brown shale formation as well as interpretations from previous studies at this location to construct a detailed paleoenvironment model for this tertiary lake the lacustrine source rock was deposited under fresh water conditions with subtle changes in the environment that resulted in significant changes in ecologies based on new data from organic petrography biomarkers microscale sealed vessel pyrolysis and characterization of the polyaromatic hydrocarbons the organic matter in the brown shale formation was determined to be sourced primarily from lacustrine organisms with a small amount of terrestrial plant input 4 methylsterane concentrations and n alkane distributions indicate that non marine dinoflagellates and botryococcus braunii a race were likely a significant portion of the local biosphere

changes in biomarker abundances and sulfur isotopes of pyrite across the permian triassic p tr schuchert dal section east greenland abstract in this study we report on biomarker abundances through parts of the permian triassic boundary ptb of schuchert dal east greenland that contains rich marine faunal records and excellent terrestrial palynological records biomarker abundances and sulfur isotopes are used to correlate the series of events including changes in element cycling and associated redox conditions of the ocean surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on earth during a mass extinction episode the upper schuchert dal formation contains a low diversity palynological assemblage ascribed to arborescent cordiaite conifer pteridosperm vegetation samples from this pre collapse interval are characterised by high abundances of dibenzofuran dbf dibenzothiophene dbt and biphenyl since these compounds have similar base structures and show comparable abundance curves it is plausible that they probably derive from a common source we propose that phenolic compounds of lignin of the woody plants present during this period could be the source for dbf dbt and biphenyl the redox conditions during this period of time also support the formation of dbf and dbt just above the extinction interval there is a dramatic decrease in the abundances of dbf and dbt which occurs at the same time as a sudden change in the stable sulfur isotopic composition 34s of pyrite indicating a change in redox conditions from oxic to anoxic euxinic conditions 34s values leading up to the extinction are highly depleted in the heavy sulfur isotope about 40 vs vcdt whilst shortly after the extinction interval much more positive isotope values are observed about 25 an inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections it is suggested that two processes are operating closely here 1 changes in redox conditions and 2 extinction and or transgression accounting for the absence of woody material

tertiary oils from upper assam basin india a geochemical study using terrigenous biomarkers abstract the upper assam basin in northeast india is a tertiary sub basin of the assam arakan basin hydrocarbons are present in the langpar formation upper palaeocene lakadong member of the sylhet formation lower eocene and the barail oligocene tipam lower miocene and girujan middle miocene formations in the basin a detailed study to understand the nature and origin of the oils from different stratigraphic horizons using terrigenous and other biomarkers has been carried out further the variation in maturities of oils occurring in different stratigraphic horizons has also been studied the study shows that rearranged oleananes oleananes and bicadinanes are present in these oils implying land plant input to their source rocks the oils have been classified into different groups using ratios of rearranged oleananes oleananes bicadinanes and steranes indicating presence of multiple source rocks in the basin with subtle variation in characteristics maturity studies show that oils from younger horizons barail tipam and girujan are more mature than oils from older horizons langpar and lakadong there is an apparent mismatch in maturity of oils as measured by different biomarker maturity parameters this is due to the mixing of two different charges of oils having different maturities and generated from two different source rock kitchens in the same reservoir principal component analysis pca of biomarker data has also been able to classify the oils into various groups a new parameter has been developed using ratios of rearranged oleananes for determining maturity of these oils

biomarker and n alkane isotope profiles for tertiary oils relationship to source rock depositional setting abstract biomarker and n alkane isotope profiles have been measured for 29 late cretaceous tertiary oils from se asia china papua new guinea new zealand and the u s a the results are interpreted with respect to six kinds of source rock depositional setting fluvio deltaic fd freshwater transitional tr lacustrine lac saline lacustrine sal marine deltaic md and marine carbonate mc a comparison of biomarker and n alkane isotope results suggests that parameters such as the oleanane hopane ratio may overestimate the higher plant contribution to marine oils the abundance of bicadinanes is much more variable than that of oleanane probably because of a specific association with the highly resinous dipterocarp hardwoods of se asia however traces do occur in an oil from outside the paleogeographic range of the dipterocarp family confirming that there is also a more general angiosperm source the bicadinane isomeric distribution is shown to depend on maturity leading to new maturity parameters which are resistant to even very heavy biodegradation retention indices based on the regular hopane series are provided for the main bicadinane and methyl bicadinane isomers and for a group of oleanane related triterpanes of unknown structure the presence of the latter compounds may indicate locally deposited as opposed to transported higher plant matter in the source source rock depositional setting is the primary control on the shape of the n alkane isotope profile with negatively sloping curves being characteristic of fd and tr oils and flat or positively sloping curves typical of marine oils the difference is probably related to the bacterial reworking of higher plant matter in the fd environment a slight isotopic anomaly at n c 17 correlates with the abundance of algal derived steranes and may indicate a minor marine contribution to the source of an fd oil

secular and environmental constraints on the occurrence of dinosterane in sediments abstract the distribution patterns of sedimentary a ring methylated steranes have changed markedly over geological time although dinosterane and its isomer 24 ethyl 4 methylcholestane have been tentatively identified in three proterozoic rock units they are either not detectable or occur in low abundance relative to 3 methyl steranes throughout most of the palaeozoic between permian and middle triassic times 260 220 ma ago 4 methyl sterane abundances in marine sediments increased markedly the presence of dinosterane in some middle triassic marine sediments is contemporaneous with the appearance of fossil cysts of uncontested dinoflagellate affinity 4 methyl steranes including dinosterane or their precursor sterenes and sterols then show a continuous presence often in high abundance in marine sediments from the late triassic through to the present day assemblages of 4 methyl steranes and their precursors but with dinosterane absent or in low relative abundance are often the predominant steroids in lacustrine sediments in the cainozoic dinosterane appears to arise predominantly from marine dinoflagellates and as a consequence is a useful biological marker for mesozoic and cainozoic marine organic matter the isomer 24 ethyl 4 methylcholestane is likely to have multiple origins although its very high abundance in tertiary lacustrine sediments and oils compared to older materials suggests that dinoflagellates could also be the source in these cases

perylene as an indicator of conifer fossil wood degradation by wood degrading fungi the occurrence of perylene in middle jurassic fossil wood and miocene xylites from poland is described along with its correlation with unsubstituted polycyclic aromatic hydrocarbons pahs as well as cellulose content both middle jurassic and miocene wood remnants were of relatively low maturity ca 0 2 0 3 vitrinite reflectance rr had excellent preservation of biomarkers and biomolecules and in the case of the middle jurassic fossil wood samples generally good preservation of anatomical structures due to early diagenetic mineralisation the results from 42 middle jurassic and 8 miocene most taxonomically defined fossil wood fragments demonstrated a negative correlation between the concentration of perylene and those of generally typical conifer biomarkers e g cadalene dehydroabietane simonellite and retene in addition good correlation r2 0 81 was observed between the ratio of perylene to the above conifer biomarkers and the ratio of pahs phenanthrene and fluoranthene and pyrene to the conifer biomarkers this implies that the high concentration of perylene in fossil wood indicate its extensive degradation during decay transport and early diagenesis we defined a conifer wood degradation index as cwdi perylene perylene cadalene retene simonellite dehydroabietane cwdi perylene perylene cadalene retene simonellite dehydroabietane and observed a wide range of values 0 001 for less degraded wood to 0 95 for highly degraded samples anatomical wood preservation was associated with cwdi values in most of the samples characterised by poorly preserved anatomy high cwdi values were observed while anatomically well preserved samples generally had lower cwdi values we determined similar 13c values for perylene from the fossil wood samples 26 4 to 27 8 whereas the values for the conifer biomarkers were slightly higher and varied from 25 6 to 26 6 in contrast pyrene was depleted in 13c 27 5 to 28 2 the carbon isotope values of perylene are consistent with an origin from wood degrading fungi

a forest fire and soil erosion event during the late devonian mass extinction abstract the late devonian mass extinction occurred in a stepwise manner and culminated close to the frasnian famennian f f boundary 372 million years ago organic molecular indices from marine sedimentary rocks at the sinsin section belgium indicate that the sequence of combustion of land vegetation soil erosion and anoxia euxinia occurred close to this boundary the increased concentrations of biomarkers indicating forest fire and soil erosion measured in the sinsin section suggest that fire became widespread at this time leading to various damaging consequences increased runoff and oceanic anoxia that caused marine extinctions magnetic susceptibility data in the sinsin section indicate a relatively dry climate spanning the f f boundary which would have encouraged forest fires the study of organic biomarkers presents several lines of evidence to link forest fire and soil erosion to the late devonian mass extinction

spike of pyrosynthetic polycyclic aromatic hydrocarbons associated with an abrupt decrease in δ13c of a terrestrial biomarker at the cretaceous tertiary boundary at caravaca spain the first vertical high resolution record of polycyclic aromatic hydrocarbons pahs of pyrosynthetic origin and the corresponding 13 c profile of a terrestrial biomarker across the cretaceous tertiary k t boundary at caravaca spain reveals the following in comparison with adjacent cretaceous marlstones the first thin horizon 0 to 0 5 cm 0 the k t boundary of the boundary clay layer is 1 enriched as much as 112 to 154 fold in typical pyrosynthetic pahs such as coronene benzo g h i perylene and benzo e pyrene and 2 shows an abrupt 13 c decrease of 1 4 1 8 in terrestrial higher plant derived n c 29 alkane the spike of pyrosynthetic pahs associated with an abrupt decrease in 13 c value of a terrestrial biomarker is interpreted to reflect the prevalence of extensive fires with subsequent 13 c decrease in atmospheric co 2 it is estimated that the geologically instantaneous combustion of 18 24 of the terrestrial above ground biomass would be necessary to account for the measured negative isotopic shift at the k t boundary on the basis of carbon mass balance between terrestrial above ground biomass and atmosphere

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

application of biological markers in the assessment of paleoenvironments of chinese non marine sediments abstract in this study we employ molecular organic geochemical data for 22 representative sediment samples from chinese non marine sedimentary basins in an attempt to characterize and assess the non marine depositonal paleoenvironments the samples investigated include oilshale shale mudstone and sodium sulphate rich sediments ranging in age from cretaceous to tertiary it is evidenced by geological and geochemical data that those sediments studied originate from lacustrine environments ranging from freshwater brackish fresh water to hypersaline the aliphatic fractions of the sediment extracts were analyzed by gc and gc ms and relative abundance of compounds and compound classes of normal acyclic and cyclic alkanes were measured from mass chromatograms the results reveal significant differences in the chemical features of the various sample groups which enable them to be characterized and identified in terms of source and or environment related parameters the diagnostic parameters that allow this assessment are the relative abundances of n alkanes acyclic isoprenoid alkanes and 4 methyl steranes hopane sterane ratio gammacerane and homohopane indexes etc in this study data interpretation was also assisted by pattern recognition through principal component analysis the results show that the sample groups of different environmental origin could be unambiguously distinguished on scores plot

effect of igneous intrusion on the organic geochemistry of a siltstone and an oil shale horizon in the midland valley of scotland abstract the effect of rapid thermal stress on the organic geochemistry of a siltstone intruded by a quartz dolerite dyke and an oil shale intruded by an alkali dolerite sill has been studied using optical petrography rock eval pyrolysis gas chromatrography and gas chromatography mass spectrometry maturity dependent ratios derived from both the aliphatic and aromatic hydrocarbon fractions corroborate the observation of raymond and murchison 1988b that the alkali dolerite sills which were intruded soon after sedimentation had a lesser effect than the later quartz dolerite intrusions the maturity parameters based on the alkylnaphthalene and alkylphenanthrene isomer ratios are more suitable for studying maturity variations in heat affected samples than those based on the commonly used aliphatic biological markers these aromatic compounds survive to higher ranks and the isomer ratios continue changing

waxy bitumen stranding in southern australia a geochemical study of multiple oil families and their likely origins abstract reports of bitumen stranding on the ocean beaches of southern australia date back to the early days of european settlement previous investigations have shown that this coastal bitumen comprises three categories of stranded petroleum waxy bitumen asphaltite and oil slicks all three varieties are physically and chemically distinct from each other and bear no geochemical resemblance to any indigenous australian crude oil this study focuses on the most common variety waxy bitumen which accounted for 90 of the strandings on six south australian beaches repeatedly surveyed during 1991 1992 geochemical analysis of 96 individual specimens collected from these survey sites and other beaches in south australia and western victoria has shown them to be variously weathered high wax crude oils of paraffinic to aromatic intermediate bulk composition elemental isotopic and biomarker differences allow their assignment to at least five oil families with inferred source facies that range from deep freshwater lacustrine through paludal and deltaic to euxinic marine possibly deposited within different sedimentary basins family 1 2 and 3 waxy bitumens all contain biomarkers derived from the freshwater alga botryococcus sp and tropical angiosperms notably dipterocarps similar biomarker assemblages are unknown in australian sedimentary basins but are common in cenozoic crude oils and source rocks throughout western indonesia family 4 waxy bitumens lack these biomarkers but do contain dinosterane and 24 n propylcholestane indicative of a marine source affinity while the carbon isotopic signatures and high pristane phytane pr ph ratios of family 5 waxy bitumens are consistent with their origin from coal rich source rocks deposited in fluvial to deltaic sedimentary successions the majority of these waxy bitumens represent an oceanic influx of non indigenous southeast asian crude oils carried into the waters of southern australia by the leeuwin current although they are likely to originate from natural seepage within the indonesian archipelago it is unknown whether the parent oils emanate from submarine seeps or from inland seepages which are then carried to the sea by rivers the common practice of tanker cleaning operations in the java and banda seas may augment the supply of natural bitumen to the beaches of australia

source controls on geochemical characteristics of crude oils from the qionghai uplift in the western pearl river mouth basin offshore south china sea abstract the qionghai uplift is a sub uplift tectonic unit in the western pearl river mouth basin though lacking source rocks itself it adjoins the wenchang a sag the wenchang b sag and the qionghai sag which contain significant source rocks for the special geological background the qionghai uplift has become an important accumulation area for oil and gas and the oils in the uplift show significant variation in important geochemical parameters in this study the geochemistry of oils in the qionghai uplift oil pools has been analyzed systematically revealing geographic differences three groups of oils were identified in the northern part of the qionghai uplift group i oils represented by the wc8 3e oil pool located in the northeast group ii oils in the middle represented by the wc13 1 oil pool and group iii oils in the southwest represented by the qh18 1 oil pool according to oil source correlations the oils of the three groups have mixed geochemical characteristics between typical oils sourced from the enping formation in the wenchang a sag and those sourced from the wenchang formation in the wenchang b sag we show that based on knowledge of hydrocarbon generation and evolution of source rocks around the qionghai uplift as well as the formative features of traps within the uplift the geochemical characteristics of the oils are mainly controlled by the distribution of mature hydrocarbon kitchens surrounding the uplift oils in the northeast of the northern qionghai uplift were mainly sourced from the enping formation in the wenchang a sag with a secondary contribution from the wenchang formation in the qionghai sag oils in the middle section are of mixed origin from the enping formation in the wenchang a sag and the wenchang formation in the wenchang b sag oils in the southwest part of the northern qionghai uplift were mainly generated from the wenchang formation in the wenchang b sag this research provides guidance for future exploration of the qionghai uplift

a molecular and isotopic study of the organic matter from the paris basin france thirteen liassic sedimentary rocks of increasing depth and three petroleums from the paris basin were studied for 13c 12c isotopic compositions and biological markers including steranes sterenes methylphenanthrenes methylanthracenes and triaromatic steroids the isotopic compositions of n alkanes from mature sedimentary rocks and petroleums fall in a narrow range 2 except for the deepest hettangian rock and the trias petroleum for which the short chain n alkanes are enriched and depleted in 13c respectively most of the molecular parameters increase over the 2000 2500 m depth range reflecting the transformation of the organic matter at the onset of petroleum generation in this zone carbonate content and carbon isotopic composition of carbonates as well as molecular parameters are distinct for the toarcian and hettangian source rocks and suggest a migration of organic matter from these two formations two novel molecular parameters were defined for this task one using methyltriaromatic steroids from organic extracts the other using 1 methylphenanthrene and 2 methylanthracene from kerogen pyrolysates the anomalous high maturity of the dogger petroleum relative to the maturity depth trend of the source rocks is used to estimate the minimal vertical distance of migration of the organic matter from the source rock to the reservoir

origin of petroleum in bangladesh fewer than 70 exploration wells have been drilled in bangladesh 207 000 km2 mostly in the eastern onshore and offshore areas making it one of the least explored countries in the world tectonic developments have controlled the accommodation space available for sediment deposition since the early cretaceous collision between the indian plate and eurasia to the north of bangladesh and between the indian plate and the burma platelet on the east provided favorable conditions for development of oligocene miocene source rocks and miocene reservoir sands in eastern bangladesh the resulting jenam bhuban boka bil petroleum system is the most active system identified to date and is dominant in eastern bangladesh hydrocarbons likely also have been generated from the organic rich shales of the miocene bhuban formation the jenam bhuban boka bil petroleum system alone is responsible for the generation of more than 16 tcf of gas in place discovered to date mostly in the surma basin of the chittagong tripura fold belt several other petroleum systems have been postulated in bangladesh together the best technical estimate of the total resource base is about 61 tcf including reserves within the discovered fields anticipated field growth and new field discoveries with the exception of small bacterial contributions in some surface seep gases and two subsurface accumulations the gases of bangladesh are thermogenic modeling results indicate that the gases and associated condensates are sourced at peak generation depths of at least 6 km many of the gas accumulations are associated with retrograde condensates whose compositions are defined by two distinct source facies and by the solution exsolution effects of vertical migration most of the condensates possess molecular signatures that indicate a major hydrogen rich angiospermous flowering land plant contribution to the organic matter of their source rock s the carbon isotope ratios of the methane in the gases and the isotopic and molecular characteristics of the associated condensates indicate a distinct source facies for petroleums of the northern surma basin relative to those in the south these isotopic and molecular results when interpreted in light of the geological framework and our basin models suggest that the oligocene jenam formation is the major contributor north of 24 4 degreesn and that the miocene bhuban formation is the major contributor to the south

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

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

productivity and paleoclimatic controls on source rock character in the aman trough north central sumatra indonesia abstract the central sumatra basin csb is a prolific oil producing basin in indonesia where a single source rock has been identified the brown shale formation of the paleogene pematang group despite the presence of a single source rock the oils in the central sumatra basin and particularly in the aman trough exhibit variable molecular and isotopic compositions previously described as reflective of lateral facies variations within the source rock analyses by gas chromatography gc gas chromatography mass spectrometry gc ms and gas chromatography isotope ratio mass spectrometry gc irms of 15 oil samples from the aman trough allowed identification of vertical and lateral facies changes within the brown shale formation as well as paleoproductivity and paleoclimatic changes that took place during deposition of this prolific source rock the molecular and isotopic data indicate the source rock for these oils was deposited in a fresh to brackish water stratified lake in which co 2 limiting conditions prevailed compound specific isotopic data also indicate that changes in paleoclimatic conditions possibly associated with the eocene oligocene paleoclimatic transition had an effect on the geochemical composition of the source rock in the aman trough

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

catastrophic soil erosion during the end permian biotic crisis organic geochemical analyses of sedimentary organic matter from a marine permian triassic transition sequence in northeastern italy reveal a significant influx of land derived diagenetic products of polysaccharides this unique event reflects massive soil erosion resulting from destruction of land vegetation due to volcanogenic disturbance of atmospheric chemistry the excessive supply of soil materials to the oceans provides a direct link between terrestrial and marine ecological crises suggesting that ecosystem collapse on land could have contributed to the end permian marine extinctions

molecular fossils in coastal bitumens from southern australia signatures of precursor biota and source rock environments abstract weathered waxy crude oil and black asphaltite tar are regularly washed ashore along the coastlines of south australia and western victoria these bitumens generally strand on medium to high energy sandy beaches in west or southwest facing bays some very weathered bitumens have been discovered in holocene dune deposits up to 200 m from the present day coastline differences in the sulphur content and carbon hydrogen and sulphur isotopic compositions of the coastal bitumens suggest that they belong to at least four oil families one of which may be emanating from submarine seeps along australia s highly faulted southern continental margin the remainder appear to be flotsam carried south from s e asia possibly sumatra the waxy bitumens families 1 3 range from paraffinic to aromatic intermediate in bulk composition and contain up to 2 6 s their density 13 38 api dictates that they are near surface drifters they have low pristane phytane ratios pr ph 2 abundant 4 methyl steranes c 30 with 24 ethyl substitution and in most cases high concentrations of botryococcane this biomarker assemblage indicates accumulation of freshwater algal source material including the remains of botryococcus sp and dinoflagellates under anoxic to suboxic conditions the additional presence of 28 30 bisnorhopane dinosterane and 24 n propylcholestane among the molecular fossils in family 3 bitumens suggests derivation from a lacustrine organic facies subject to marine incursions or alternatively mixing in the reservoir of two end member lacustrine and marine oil types trace amounts of oleanane and isomeric bicadinanes in the waxy bitumens constrain the age of their source rocks late cretaceous or younger and also preclude their local derivation an indonesian origin is considered likely implying long distance transport by surface ocean currents the family 4 bitumens 5 api are bottom drifters these sulphur rich 3 6 s aromatic asphaltic crudes have molecular signatures that include pr ph 1 c 27 c 29 c 28 c 30 desmethyl steranes dinosterane dominant over 4 methyl 24 ethylcholestane an enhanced concentration of 28 30 bisnorhopane relative to hopane and the absence of 2 or 3 methylhopanes a distal anoxic marine facies of the late cretaceous belfast mudstone in the eastern otway basin or its lithostratigraphic equivalent in the duntroon basin are possible local sources of the asphaltic bitumens

coastal bitumens from western australia long distance transport by ocean currents abstract samples of weathered bitumens were collected from granite rocks and quartz sand beaches near the high water mark along the west and south coasts of western australia samples were subjected to analysis using gc and gc ms techniques the proportions of n alkanes and branched and cyclic compounds in the samples were variable and the variation was attributed to differences in sample weathering more detailed analysis of the bitumens for biomarkers revealed the presence of botryococcane 4 methylsteranes bicadinanes and oleanane the occurrence of these compounds has also been observed in crude oils from the s e asian region the presence of bicadinanes has been attributed to a source contribution from an angiosperm currently confined to tropical regions and indicates that the source rocks from which the bitumens were derived were deposited after late cretaceous times the absence of late cretaceous and tertiary sediments deposited in lower latitudes in the northwest and western offshore basins of australia suggests a non local source of the bitumens a mechanism involving the leeuwin current has been proposed to account for transport of these bitumens which are presumably sourced from locations in s e asia

geophysical and hydrological evaluation of two bog complexes in a northern peatland implications for the distribution of biogenic gases at the basin scale 1 ground penetrating radar gpr was used to determine peat basin geometry and the spatial distribution of free phase biogenic gasses in two separate units of a northern peatland central and southern unit of caribou bog maine the central unit is characterized by a deep basin structure 15 m maximum depth and a raised eccentric bog topographic profile up to 2 m topographic variation here numerous regions of electromagnetic em wave scattering are considered diagnostic of the presence of extensive free phase biogenic gas in contrast the southern unit is shallower 8 m maximum depth and has a slightly convex upwards bog profile less than 1 m topographic variation and areas of em wave scattering are notably absent the biogenic gas zones interpreted from gpr in the central unit are associated with 1 wooded heath vegetation at the surface 2 open pools at the surface 3 high water table elevations near the center of the basin and 4 a region of overpressure at approximately 5 m depth immediately below the zone of free phase gas accumulation the latter suggests 1 a transient pressure head associated with low hydraulic conductivity resulting from the biogenic gasses themselves or confining layers in the peat that restrict both gas release and groundwater flow and or 2 overpressure in the peat column as a result of the gas buildup itself in contrast the southern unit where zones of em scattering are absent is characterized by 1 predominantly shrub vegetation 2 a lack of open pools 3 only minor variations less than 1 m in water table elevation throughout the entire unit and 4 generally upward groundwater flow throughout the basin the results illustrate the nonuniformity of free phase biogenic gas distribution at the peat basin scale and provide insights into the processes and controls associated with ch4 and co2 accumulation in peatlands

30 norhopanes their occurrence in sediments and crude oils abstract sediments and crude oils have been analysed using gc ms techniques and shown to contain two homologous series of hopanes namely 30 nor 17 h hopanes and 25 30 bisnor 17 h hopanes as well as the common 17 h hopanes homologues c28 to c34 of the 30 nor 17 h hopane series have been identified in crude oils associated with carbonate source rocks the abundances of these hopanes relative to the 17 h hopanes in the soluble organic matter from carbonate sediments has been shown to depend upon sample maturity the more mature samples having higher relative abundances of these norhopanes a comparison of the relative abundances of the norhopanes in the soluble organic matter of sediments and in the hydrocarbon fraction released when the extracted sediments were pyrolysed showed that the 30 nor 17 h hopanes were more abundant in the pyrolysis product these observations indicate that the proportion of norhopanes relative to normal 17 h hopanes in bound form in the kerogen is greater than that present in the soluble form and so kerogen cracking proceeds with increased maturity of the sediments and a relative enrichment of these norhopanes occurs in the soluble fraction the series of 25 30 bisnor 17 h hopanes has been identified in a severely biodegraded crude oil from a putative carbonate source this observation together with the reported occurrence of enriched 25 norhopanes in severely biodegraded crude oils suggests that 25 30 bisnor 17 h hopanes may be biomarkers for severely biodegraded crude oils from carbonate rich source rocks

perylene occurrence alkylation and possible sources in deep ocean sediments abstract 81 deep ocean sediment samples obtained from the dsdp ipod program legs 63 66 and six gravity cores from dsdp ipod leg 64 guaymas basin gulf of california site survey cruise sio were analyzed for perylene s perylene was found to be most abundant in anoxic diatomaceous sediments containing moderate amounts of silts and or clays elevated perylene yields normalized to organic carbon contents coincided with enhanced preservation of autochthonous tetraterpenoid and tetrapyrrole pigments indicating a requirement of anoxia in the formation of perylene strongly euxinic conditions correlate with decreased perylene yields but not its total absence as found for strongly aerobic deposition and or redeposition perylene alkylation occurs in response to increasing in situ temperatures alt sub bottom depth this alkylation was found to begin with the generation of methyl c 1 perylene and to eventually yield a perylene alkyl perylene homologous series in decreasing abundance through the equivalent of c 3 trimethyl methyl ethyl propyl perylene the realm of most intense perylene alkylation for quaternary or pliocene miocene sediments corresponds with present in situ temperatures of 40 50 c or 30 35 c respectively thus the degree of perylene alkylation may represent an organic indicator for the thermal history of immature sediments geological phenomena such as reworking and igneous intrusions were found to complicate downhole perylene alkylation patterns a substituted c4h7o2 perylene was isolated from several anoxically deposited diatomaceous oozes and may represent one of the many possible perylene precursors the possible source compounds and biota for sedimentary perylene are discussed in light of the present study and review of past reports

the nature and influence of fire in carboniferous ecosystems fusain occurs widely in carboniferous coals and sediments it is now recognised to represent charcoal and be the product of wildfire the occurrence of fire is partly constrained by atmospheric oxygen levels availability and nature of fuel and by aspects of climate rainfall and seasonability in particular the majority of fires in the carboniferous were probably started by lightning strikes or by volcanic activity experiments on the charring of modern plants has shown that the reflectance of charcoal and hence fusain is directly related to temperature of formation different fire types may yield fusain assemblages of differing reflectance spectrums but it may be significant that many modern charcoal assemblages yield only semifusinites as seen by reflectance microscopy the significance of these findings is assessed in relation to the use of fusinites and semifusinites as depositional indicators as interpreted from coal petrology fires may have a dramatic effect on ecosystems not only causing changes in vegetational succession but also severe erosion can occur following a major fire which can be traced in depositional systems in this paper we document three major carboniferous sedimentary systems affected by fire clastic sedimentary systems using extensive fusain deposits in mid lower carboniferous near shore sediments in donegal ireland volcanic systems using late early carboniferous volcaniclastic sequences in the midland valley of scotland and coal and coal bearing sequences in the upper carboniferous westphalian b of the pennine basin england in the later settings the influence of fire in peat formation and succession is assessed in addition data on the vegetational composition of charcoal assemblages is considered it is concluded that fire plays a major role in many carboniferous ecosystems

polycyclic aromatic hydrocarbons of pyrolytic origin in ancient sediments evidence for jurassic vegetation fires abstract polycyclic aromatic hydrocarbon pah distributions in an upper jurassic succession from offshore korea bay basin were consistent with a pyrolytic source being dominated by non alkylated species levels of these pahs were significantly higher in samples containing abundant fusinite macerals which are believed by some to be the product combustion the data were consistent with a pah origin from periodic conflagration throughout the upper jurassic of vegetation adjacent to a tectonically formed lake distribution of pahs exhibited some differences from those of combustion origin in recent and some ancient sediments and were characterized by the dominance of the highly peri condensed compounds benzo e pyrene benzo g h i perylene and coronene this characteristics reflects either preferential formation or preferential preservation under the prevailing sedimentary conditons of the highly peri condensed structures

oleanane parameter verification by quantitative study of the biomarker occurrence in sediments of the niger delta abstract the variation of the absolute concentration of oleananes in three selevted sedimentary columns of the tertiary niger delta is paralleled by the corresponding oleanane parameter op profile thereby confirming that the latter can be utilized for estimating the relative contribution of terrigenous organic matter it is shown that op features a dynamic range especially at the oil generative window ogw and can precisely delimit the top of the ogw which for the niger delta is shown to coincide approximately with the 80 c isotherm and ro 0 55 this study provides the first direct evidence of the inadequacy of vitrinite reflectance as a maturity parameter for type iii kerogen furthermore based on the new findings an alternative model for oleanene oleanane interconversions in the geosphere is proposed

bicadinanes in oils from the surma basin bangladesh abstract bicadinanes c 30 pentacyclic triterpanes have only been reported in crude oils and sediment extracts from s e asia the present investigation indicates that they are also widely present in land plant derived tertiary oils from the surma basin of n e bangladesh oleanane is also abundant in these oils though its distribution does not correlate with those of the bicadinanes this is consistent with separate specific land plant sources for these two classes of triterpanes and with the formation of bicadinanes during maturation of polymerised angiosperm tree resin

geochemical characterization and source investigation of oils discovered in khoraghat nambar structures of the assam arakan basin india abstract we examined the geochemical compositions of the newly discovered bokabil and sylhet oils and of the extracts of potential source rock samples from the khoraghat nambar area of the assam arakan basin india stable carbon isotopic compositions and a number of biomarkers indicate that oils in the bokabil formation early to middle miocene can be correlated across the khoraghat and nambar fields however oil from the sylhet formation middle to late eocene is distinct from those in the bokabil formation late eocene to early oligocene barail coal shale and middle to late eocene kopili shale sequences are identified as potential source rocks both strata contain organic matter predominantly derived from higher land plants however different organofacies exist for barail coal shale and kopili shale sequences that can be distinguished by the stable carbon isotopic compositions and biomarker distributions an oil source correlation study shows that barail rock extracts are genetically correlatable with the bokabil oils whereas kopili rock extracts have similar source specific parameters to those of the sylhet oil thus the study suggests the presence of two petroleum systems in the khoraghat nambar area the barail bokabil and the kopili sylhet petroleum systems barail and kopili sediments from the study area are of lower maturity than the oils suggesting that the actual source strata are more mature equivalents likely to be present in the naga schuppen zone therefore areas in and around the naga schuppen zone where better reservoir facies are expected are favoured targets for further exploration

higher plant biomarker signatures of early eocene sediments of north eastern india abstract the biomarkers molecular fossils of paleobiota have been studied in detail from a coal bearing sequence of early eocene lakadong sandstone member of sylhet formation of upper assam basin ne india using gas chromatography mass spectrometry corresponding hydrocarbon source potential of the same unit has been studied using rock eval pyrolysis the rock eval data suggest dominant terrestrial land plant contribution i e type iii kerogen and the sediments of the section had entered the early stage of catagenesis the alkane and isoprenoid distributions are characterized by odd over even preference oep 1 1 1 2 of n alkanes and high pristane phytane ratio 2 9 7 6 which corroborate the rock eval data the distribution of aliphatic biomarkers is characterized by dominance of c24 tetracyclics over c23 tricyclics high concentration of des e hopane moderate to high c29 c30 hopane ratio extremely low oleanane index and low c35 homohopane index the extremely low oleanane index is correlated with a high degree of aromatization of oleanane skeleton favoured by acidic swampy depositional environment the presence of diterpanes at the base of the early eocene section indicates contribution from gymnosperms coniferales order of land plants whereas angiospermous biomarkers with oleanoid skeleton are also preserved this pattern subsequently evolved to angiosperm dominated towards the top of the section with no gymnosperm signature indicating possible climatic variation during the early eocene towards the top of the section presence of bicadinanes indicates contribution of dipterocarpaceae family of trees and advent of the evergreen tropical rain forest element in eastern india in early eocene similar to the pattern found in western india e g cambay and kutch basins

oceanic transport of fossil dammar resin the chemistry of coastal resinites from south australia abstract fragments of resin and fossilised resin resinites occasionally wash ashore along the southern australian coast chemical and isotopic analyses were carried out on a suite of coastal and reference resinites to determine the likelihood of a local as opposed to a distant origin all of the coastal resinites were found to contain a polymer based on the sesquiterpenoid cadinene skeleton and were markedly different to the diterpenoid resinites found in local victorian coals the coastal resinites closely resemble both fossil and recent dammar resin a material associated primarily with the tropical angiosperm hardwoods of southeast asia and one which has no known australian source minor variations in the composition of our resinite samples are attributed to differences in their thermal history these findings confirm the viability of long distance oceanic transport not only for the resinites but also for the waxy bitumens that strand along the same coastline analytical data on the coastal resinites also help to clarify the role of dammar resin in generating bicadinanes a class of source and age specific triterpanes found commonly in the cainozoic oils and sediments of southeast asia

petroleum charge history in the baiyun depression and panyu lower uplift in the pearl river mouth basin northern south china sea constraints from integration of organic geochemical and fluid inclusion data the source thermal maturity and charge history of oil and gas condensate in the baiyun depression and the panyu lower uplift were determined using organic geochemical and fluid inclusion data nearly all the gas condensates and oil in the study area originated from eocene enping formation source rocks whereas the condensate fluids in the eastern area originated from the enping and zhuhai formations the condensate fluids have a relatively low thermal maturity with a calculated vitrinite reflectance equivalent that typically ranges from 0 8 to 1 0 based on the c29 sterane isomerization ratios and aromatic hydrocarbon maturity parameters four types of oil inclusions with various fluorescence colors yellow blue and api gravities 25 44 were recognized in the oligocene and lower miocene reservoir units which suggest multiple oil charging events the homogenization temperatures of the fluid inclusions recorded the oil charge events accompanying large scale hot fluid movement which was most likely caused by the charging of high temperature natural gas from the deeper wenchang formation the trapping pressures of the oil inclusions and the reconstructed burial histories were used to determine the timing of oil charge the main oil charge occurred from 16 7 ma throughout the baiyun depression and panyu lower uplift whereas the panyu lower uplift experienced an additional oil charge from 5 0 ma the natural gas charge occurred during the main oil charging period and may continue to the present day multiple physical processes such as gas injection without gas exsolution gas washing with gas exsolution and migration fractionation have played important roles in gas condensate formation and controlling the petroleum distribution in the baiyun depression and panyu lower uplift

geochemical composition and origin of tertiary oils in the yinggehai and qiongdongnan basins offshore south china sea abstract this study comprehensively characterizes the geochemical compositions of tertiary crude oils in the yinggehai and qiongdongnan basins offshore south china sea and differentiates their source properties using chemical and isotopic data the oils in the two basins have distinct source characteristics the majority of the oils from the yacheng yc field in the qiongdongnan basin are commonly marked by high pr ph ratios mostly from 4 5 to 7 0 unusually abundant angiosperm derived compounds and a domination of c29 in diasteranes suggesting a predominantly terrigenous organic source in contrast the oils from the dongfang df and ledong ld fields in the yinggehai basin have relatively lower pr ph values 2 5 5 5 and a low amount of bicadinanes moreover some oils in this basin contain abundant 4 methylsteranes and detectable c30 desmethyl steranes the difference in the molecular composition is also apparent with regard to the aromatic hydrocarbons the former oils contain more abundant biphenyls fluorenes and 2 phenylnaphthalene than the latter ones the oils from the qiongdongnan basin are relatively depleted in 13c and have 13c values of the whole oil in the range of 24 9 to 26 9 consistent with the great terrigenous input in contrast the yinggehai oils are isotopically heavier with 13c values from 21 6 to 23 6 typical of a marine isotope signature correspondingly their n alkane isotopes have different 13c ranges and exhibit distinct distribution profiles based on the oil source rock correlation the oils in the yc field were generated from the coastal plain swamp and shallow marine strata of the oligocene in the qiongdongnan basin while the yinggehai oils were sourced from the miocene shallow marine mudstones in the basin

the origin and fate of 4 methyl steroid hydrocarbons i diagenesis of 4 methyl sterenes abstract treatment of 4 methylcholest 4 ene under mild acid conditions at low temperatures gives chemical evidence for certain features seen in the distributions of sedimentary 4 methyl steroid hydrocarbons and further indicates that many low temperature diagenetic reactions of steroids are explicable in terms of acid catalysed rearrangements specifically the results provide i indirect evidence that the 4 ene skeleton is a key intermediate in the dehydration of 4 methyl stanols in sediments ii an explanation for the distribution of 4 methyl sterenes and a nor sterenes in the lacustrine messel shale eocene iii an explanation for the presence of 4 methyl steranes in relatively immature sedimentary rocks despite the precursor stanols having the 4 methyl configuration with increasing maturity in the paris basin shales lower toarcian the less stable 4 methyl steranes decrease gradually in abundance relative to their 4 methyl counterparts at a rate fairly similar to the change in pristane stereochemistry