significant changes in land vegetation and oceanic redox across the cretaceous paleogene boundary abstract the impact of an extraterrestrial body 65 5 ma caused the so called cretaceous paleogene k pg event that resulted in a mass extinction and rapid changes in the surface environment on earth here we report changes in land vegetation and oceanic redox across the k pg boundary at caravaca southeastern spain using biomarkers the results reveal that the basal 3 mm thick layer of the k pg boundary clay is marked by a rapid increase in the concentration of terrestrial long chain n alkanes and dibenzofuran indicating the destruction of land vegetation and an increase in the supply of terrestrial organic matter into the marine environment during the deposition of the k pg boundary clay this layer also records a rapid increase in the concentration of dibenzothiophenes which indicates a change in redox conditions from oxic to anoxic euxinic conditions in the intermediate water over the seafloor the low oxygen conditions could have been caused by an increase in the influx of terrestrial organic matter into the ocean a rapid increase in the concentration of retene and retene cadalene occurred during the deposition of the upper part of the boundary clay 10 kyr after the mass extinction indicating the recovery of conifers which greatly decreased at the k pg boundary

24 norcholestanes as age sensitive molecular fossils biomarkers molecular fossils are organic compounds in holocene to precambrian sedimentary deposits that can be related to specific chemical compounds produced in the biosphere we demonstrate here that 24 norcholestane biomarkers i e c26 steranes saturated hydrocarbons having a steroid skeleton can be useful to constrain the age and paleolatitude of geologic samples the biological precursors of 24 norcholestanes remain unclear but samples from more than 100 basins provide evidence that 24 norcholestanes may be derived directly or indirectly from diatoms ratios of 24 norcholestanes to 27 norcholestanes show an initial increase above background in jurassic oils but they increase dramatically in cretaceous oils coincident with diatom evolution the highest ratios are found in oils and rock extracts from oligocene or younger marine siliceous source rocks in which the sources were deposited at paleolatitudes 30 n

the late quaternary calcareous nannoplankton assemblages from three cores from the tasman sea abstract the composition of the late quaternary calcareous nannoplankton in three deep sea cores rc12 113 z 2108 and gc 3 located along a n s transect at three different latitudes 25 33 44 s in the tasman sea has been investigated the shift in floral dominance from small gephyrocapsa to small placoliths labelled here small placolith and then to emiliania huxleyi is recognized at stage 5 and stage 4 respectively in cores rc12 113 and z 2108 however the occurrence of small gephyrocapsa and small placolith displays a seesaw relationship in core gc 3 which is located today just north of the subtropical convergence east of tasmania gephyrocapsa muellerae and coccolithus pelagicus increase their abundance geographically southwards and stratigraphically during glacial periods whereas the percentage abundances of florisphaera profunda and umbilicosphaera sibogae demonstrate reverse patterns the relationships between the percentage abundance of each nannoplankton species and the 18 o record for three cores are discussed in detail a transfer function for estimating past sea surface temperatures tn is attempted here it is based on core top data from the tasman sea and provides a good relationship between some calcareous nannoplankton assemblages and modern mean summer sea surface temperatures the tn value shows a good correspondence with the 18 o record in all three cores core gc 3 is much affected by caco 3 dissolution in comparison with cores rc12 113 and z 2108 the calcareous nannoplankton dissolution patterns recognized in the three cores do not show a systematic correspondence with the 18 o record of interest however is the good preservation peaks that are recognized in all three cores at the transitions from glacial to interglacial events

biological markers and carbon isotope composition of organic matter in the upper cretaceous coals and carbonaceous shale succession jiza qamar basin yemen origin type and preservation abstract bituminous coals and carbonaceous shales located in the jiza qamar basin on the eastern yemen were analysed based on a combined investigation of organic geochemistry and petrology to define the palaeodepositional environment condition organic matter inputs and their thermal maturity carbon isotope compositions and various biomarkers were performed on coals and carbonaceous shales within the upper cretaceous mukalla formation in the jiza qamar basin the 13 c values range from 29 2 to 24 5 with average values around 26 7 whereas the organic carbon contents in most sediment samples are consistently high 3 indicating that the organic matter in the mukalla coal and carbonaceous shale sediments has a predominantly terrigenous origin with slightly marine influence during burial this has also been identified from kerogen microscopy which is characterized by dominance of vitrinite and liptinite organic matter the investigated biomarkers indicated that the mukalla coals and carbonaceous shales contain high contribution of land plants with a minor aquatic organic matter input that was deposited in a fluvial to deltaic environments and preserved under relatively oxic conditions this has been achieved from acyclic isoprenoids terpane and sterane biomarkers of a saturated hydrocarbon and dibenzothiophene alkylnaphthalene and methylphenanthrene biomarkers of an aromatic hydrocarbon based on the analysed biomarker thermal maturity indicators it may be deduced that the mukalla coals and carbonaceous shales in the jiza qamar basin have entered an early mature to mature stages for hydrocarbon generation this is also supported by vitrinite reflectance values of 0 63 0 83 ro indicative that these sediments have reached oil window maturity

biological origin of tetracyclic diterpanes n alkanes and other biomarkers found in lower carboniferous gondwana coals niger abstract the saturated hydrocarbons of coal samples of the anou araren mine tim mersoi basin niger republic have been studied by gc and gc ms chromatograms revealed rather unusual n alkane distributions dominated by compounds in the c 20 c 23 range and showing a rapid and irregular decrease towards higher molecular weights these signatures appear to be typical of the paleozoic gondwana swamps flora unlike typical low maturity terrestrial organic matter characterized by a dominance of odd carbon number n alkanes in the c 27 c 33 range which could be attributed to angiosperms the presence of large amounts of polycyclic diterpanes ent beyerane phyllocladanes and kauranes is unexpected in samples of that age since these compounds are usually thought to be derived from conifers which supposedly had not yet evolved at the time a more likely explanation is that these diterpanes could be derived from biological precursors of the conifers

geochemical implications of the lipid composition of thioploca spp from the peru upwelling region 15 s thioploca a genus of colorless sulphur oxidizing filamentous bacteria constitutes as much as 80 of the biomass in dysaerobic surface sediments o2 0 1 ml l bottom water in the coastal upwelling regimes of peru and chile the lipid composition of thioploca collected from sediments from the oxygen minimum zone in the peru upwelling region near 15 s is presented here and we provide the first assessment of the influence of thioploca on organic compound distributions in upwelling regime sediments since marine species of thioploca have been found only in dysaerobic surface sediments of upwelling regimes biomarkers for this organism may be useful in identifying similar depositional conditions in the sedimentary record thioploca dry was found to be 3 8 4 1 wt lipid three fatty acids cis 16 1 9 16 0 and cis 18 1 11 accounted for 69 72 of this lipid hydroxy fatty acids hopanoids and hydrocarbons were conspicuously absent from the thioploca the thioploca was found to contain cyclolaudenol a c31 sterol with an unusual structure diagenetic alteration products of this sterol may serve as markers for thioploca input to sedimentary organic matter and hence as markers for paleo upwelling depositional environments in the sedimentary record

timing and patterns of the frasnian famennian event evidences from high resolution conodont biostratigraphy and event stratigraphy at the yangdi section guangxi south china abstract continuous centimeter scale sampling for conodonts with microfacies and carbon isotope analysis has been carried out across the frasnian famennian f f transition at the yangdi section guangxi south china the newly revised conodont biostratigraphy reveals a succession of six zones ranging from the upper palmatolepis rhenana zone to lower palmatolepis crepida zone in ascending order based on a detailed analysis of conodont abundance and diversity changes through the section two intervals involving significant conodont faunal changes were recognized in the uppermost palmatolepis linguiformis zone at the yangdi section the first conodont change occurred at the transition between the lower and upper pa linguiformis zone and is marked by the disappearance of pa linguiformis accompanied by the successive disappearances of pa eureka pa rhenana pa nasuta pa gigas ad ioides and ad nodosa the second conodont change appeared in a horizon equivalent to the uppermost upper kellwasser horizon ukh and is indicated by the elimination of nearly all frasnian palmatolepids ancyrodellids and polygnathids furthermore the second conodont change is coincident with the decimation of ostracods and tentaculitids and is synchronous with the turnovers of conodont biofacies in addition the onset of the 13 c carb perturbation is a little earlier than the second conodont change with the maximum amplitude of excursion right at the start of the famennian therefore we conclude that the second conodont change represents the f f mass extinction based on the temporal correlation among 13 c carb excursions pelagic faunal changes and conodont biofacies turnovers during the f f boundary interval according to the high resolution conodont biostratigraphy together with cyclostratigraphy the uppermost ukh and whole ukh contain 1 and 12 bundle cycles respectively thus the time span of the mass extinction and the entire upper kellwasser crisis lasted 16 18 kyr and 200 kyr respectively

origin and mixing of crude oils in triassic reservoirs of mahu slope area in junggar basin nw china implication for control on oil distribution in basin having multiple source rocks abstract the origin of crude oils and their varied geochemical features along the western and northern slope of the mahu depression in the junggar basin has been controversial based on the molecular and isotopic geochemistry of hydrocarbons from 46 drill stem test crude oil samples and 36 core samples three oil groups i ii iii and five subgroups i 1 i 2 ii iii 1 and iii 2 have been recognized and oil source correlations have been established the subgroup i 1 oils originated mainly from lower permian fengcheng p 1 f carbonate source rocks subgroup i 2 from p 1 f mudstone source rock and group ii oils from middle permian wuerhe p 2 w mudstone source rock whose potential was underestimated in the past group iii consists of mixed oils i e subgroup iii 1 received contributions from p 1 f carbonates and p 2 w mudstones and subgroup iii 2 is a mixture of oils from p 1 f mudstones and p 2 w generated oils in order to determine the main source rocks the laboratory oil mixing experiments were carried out tricyclic terpane biomarker parameters tts were used to quantify the source contributions whole oil carbon isotope ratios were also used to verify the proportions of different oils in each mixture the results show that subgroup iii 1 oils have diverse mixing ratios in different reservoir subgroup iii 2 oils are mainly from p 1 f mudstones and p 2 w source rock contributes little finally the accumulation process of oil fields along the northern slope of the mahu depression was analyzed and the contributions from different sources were revealed this study provides an effective quantitative method to identify contributions from different lacustrine source rocks to mixed oils in the mahu depression which could be helpful in predicting location and composition of undiscovered oils

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

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

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

depositional environment and organic geochemistry of the upper permian ravnefjeld formation source rock in east greenland the upper permian ravnefjeld formation in east greenland is composed of shales that laterally pass into carbonate buildups and platforms of the wegener halvo formation the ravnefjeld formation is subdivided into five units that can be traced throughout the upper permian depositional basin two of the units are laminated and organic rich and were deposited under anoxic conditions they are considered good to excellent source rocks for liquid hydrocarbons with initial average toc total organic carbon values between 4 and 5 and hi hydrogen index between 300 and 400 the cumulative source rock thickness is between 15 and 20 m the source rocks are separated and enclosed by three units of bioturbated siltstone with a toc of less than 0 5 and an hi of less than 100 the e siltstones were deposited under relatively oxic conditions the organic geochemistry of the source rocks is typical for marine source rocks with some features normally associated with carbonate evaporite environments low pr ph pristane phytane low cpi carbon preference index distribution of tricyclic and pentacyclic terpanes the establishment of anoxic conditions and subsequent source rock deposition was controlled by eustatic sea level changes the subenvironment paleogeographic setting influx of carbonate material water depth salinity has some influence on a number of bulk parameters toc hi relations toc ts total sulfur relations and in particular biomarker parameters such as pr ph and terpane ratios all the basal shales or shales in the vicinity of carbonate buildups or platforms are characterized by low pr ph high c23 tricyclic terpanes and high c35 and c33 hopanes

a spike of woody plant biomarkers in the deep sea iridium layer at the cretaceous paleogene boundary abstract at the cretaceous paleogene k pg boundary 66 million years ago the chixulub impact resulted in significant environmental changes and a mass extinction of dinosaurs and marine invertebrates such as ammonites here we report that accumulation of woody plant biomarkers in the deep water occurred in the iridium anomaly at 700 km from the impact crater the results reveal that the concentration of terrestrial organic molecules derived from woody plants namely biphenyl and dibenzofuran shows synchronized changes and increases abruptly in the red layer fine ejecta which has an iridium spike above tsunami like coarse deposits indicating a significant increase in the influx of woody plant fragments into the ocean a few years after the impact long chain n alkanes and cadalene derived from land vegetation in the tsunami like coarse deposits prior to the transportation of trees were also transported to the deep sea this implies that transportation of grass to the deep sea started within a few days of the bolide impact transportation of trees then began a few years later a rapid increase in the concentration of dibenzothiophenes also occurs in the red layer indicating that low dissolved oxygen conditions had expanded in the bathypelagic zone over the seafloor an increase in the influx of terrestrial organic matter into the deep ocean could have resulted in the low dissolved oxygen conditions furthermore the stratigraphic distribution of planktonic foraminifera at beloc shows that cretaceous planktonic foraminifera became extinct as the result of an asteroid impact

determination of thermal maturity and organic matter type by principal components analysis of the distributions of polycyclic aromatic compounds abstract the thermal maturity and organofacies sensitivity of polycyclic aromatic compound pac distributions was explored by examination of the aromatic fractions of solvent extracts from a diverse set of 53 shales coals and kerogen macerals which have undergone either natural or artificial maturation and which represent all three principal sedimentary organic matter om types systematic changes with maturation were observed in the following groups of isomers tri and tetramethylnaphthalenes methyl and dimethylphenanthrenes methyl and dimethyldibenzothiophenes methylpyrenes and methylchrysenes the maturity differences were quantified by mathematical ratios of the relative concentrations of the more thermally stable isomers to the less stable on the basis of theoretical considerations and empirical observations the pac maturity parameters unlike those derived from saturated biomarker stereoisomers are typically effective across the entire oil generation window to compensate for the effects of om type on the maturity parameters they were combined using principal components analysis the resulting first principal component was in good agreement with independent indicators of maturity the relative distributions of c0 c3 alkylphenanthrenes dibenzothiophene methyldibenzothiophenes and methyldibenzofurans were evaluated by a separate principal components analysis the results permitted an independent grouping of the samples by om type and suggested additional simple molecular ratios that allow graphical recognition of om type including the ratio of dibenzothiophenes to dibenzofurans and a ratio using c2 alkylphenanthrene isomers

the influence of the late devonian kellwasser events on deep water ecosystems evidence from palaeontological and geochemical records from south china abstract the late devonian frasnian famennian f f event consisting of the lower and upper kellwasser events had a severe impact on shallow water ecosystems while the effect on deep water ecosystems is ambiguous in order to recognize the kellwasser events and to evaluate their influences on the deep water ecosystems a newly refined conodont biostratigraphic framework spanning the lower palmatolepis rhenana zone to the pa delicatula platys zone has been established in the nandong section basinal facies guangxi south china the upper devonian lower and upper kellwasser horizons lkh and ukh have been recognized in the deep water facies on the basis of lithological variations biological turnovers and positive carbon isotope 13ccarb excursions the lkh is characterized by the enrichment of marine nektonic communities e g conodonts homoctenids and entomozoacean ostracods whereas the top of the ukh is barren of fossil organisms suggesting that the upper kellwasser event had a more severe effect on nekton than the lower kellwasser event the upper kellwasser uk 13ccarb positive excursion lags behind the enrichment of cu ni mo and v indicating that the uk 13ccarb positive excursion was probably related to elevated primary productivity which induced oxygen depletion in the water column the uk 13ccarb positive excursion peak prior to the f f boundary indicates a more limited effect of riverine influx on the deep water setting which suggests that the regional palaeogeographic configuration played an important role in the carbon cycle

the devonian and carboniferous of the moscow syneclise russian platform stratigraphy and sea level changes abstract the moscow syneclise is a vast sedimentary basin located in the centre of the east european platform the palaeozoic sequence of this syneclise and especially its devonian carboniferous part is most suitable for sea level fluctuation analysis the devonian and carboniferous sediments consist mainly of shallow marine carbonates containing several minor terrigenous intervals they attain total thicknesses of up to 1 5 km the modern stratigraphic scale includes 33 regional stages for the devonian and 32 for the carboniferous correlation of this scale with global scales is supported by conodont miospore and foraminifera zonations the new calibrated devonian and carboniferous relative sea level curves for the moscow syneclise reflect late eifelian mid frasnian early tournaisian late visean early serpukhovian and moscovian gzhelian transgressions several of these sea level changes which are particularly evident on the margins of the moscow syneclise originated in response to differential tectonic movements of the voronezh anteclise and the tokmovo uplift as well as to vertical oscillations of the entire east european craton

aromatic hydrocarbon biomarkers in terrestrial organic matter of devonian to permian age abstract this paper presents the results of a detailed study on the occurrence and distribution of alkylnaphthalenes and alkylphenanthrenes in 39 coal and sediment samples from the late palaeozoic containing predominantly terrestrial organic matter most of the samples represent the euramerian flora realm and originate from locations beyond the variscan front in eastern northern and central europe i e especially england and the moscow basin the samples are of relatively low maturity 0 32 to 1 80 rr and consist mainly of mixtures of type iii and ii kerogen quantification of the c0 to c4 naphthalenes and the c0 to c4 phenanthrenes showed that these compound classes were highly abundant in all samples aromatic hydrocarbon maturity parameters in general are in good agreement with measured vitrinite reflectance values 1 2 7 trimethylnaphthalene an assumed diagenetic product of oleanane type biomarkers was present in all investigated samples this observation provides evidence that oleanane type lipids were biosynthesised by organisms predating the evolution of angiosperms or that assumed formation pathways for 1 2 7 trimethylnaphthalene are insecure 1 2 8 trimethylphenanthrene was significantly enriched in samples from the permian and the one sample from the devonian investigated in this study the precursor s of 1 2 8 trimethylphenanthrene therefore may have been produced by organisms which were least abundant in the carboniferous depositional environments represented by our samples

the late devonian frasnian famennian event in south china patterns and causes of extinctions sea level changes and isotope variations abstract the frasnian famennian f f event may be recognized in various facies areas in south china in the pelagic cherty basin facies both lower and upper kellwasser events can seemingly be recognized in the deeper water carbonate facies the f f event level is well controlled in light of conodont biostratigraphy in the shallow water carbonate and mixed carbonate shale facies the f f boundary may be defined by clear taxonomic distinction in benthic fossils articulate brachiopods and corals as well as evidence from minor pelagic fossils post extinction recovery rate of benthic organisms differs in different facies settings and different taxonomic groups in open shallow water platform to inter platform depression areas brachiopods seem to recover quickly probably in the middle pa triangularis zone benthic ostracodes seem to recover at a later stage recovery of rugose corals did not happen until the uppermost famennian three steps of the f f mass extinction are postulated 1 extinction of diverse brachiopods including most atrypids 2 extinction of pelagic conodonts 3 extinction of both benthic faunas very abundant and diverse rugose corals and ostracodes and pelagic conodonts evidence of an end frasnian regression in south china is clear particularly in shallow water settings however in deeper water settings the picture is complicated with evidence of both sea level rise and fall in the latest frasnian it may be assumed from overall data so far known that crustal evolution itself and associated multiple volcanic hydrothermal activities may have mainly caused frequent and rapid climatically warming cooling alterations and sea level changes as well as marine ecologic collapse eutrophication microbial blooming seawater acidification and anoxia which may explain the f f extinction pattern in south china

occurrence and geochemical significance of 1 2 5 6 tetramethylnaphthalene analysis of aromatic hydrocarbon fractions of selected coal and shale samples reveals the predominance of two specific polyalkylnaphthalenes which have been identified as 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnaphthalene the maturity of the samples is such that the source effect on the formation of individual molecules from biological precursors is expected to be recognisable these alkylnaphthalenes are thought to be diagenetically derived from pentacyclic triterpenoids via 8 14 seco triterpenoids which are also detectable in some of the samples investigated it is proposed that 1 2 5 6 tetramethylnaphthalene in the coal samples is formed by cleavage and methyl shift reactions from geminal c 4 methylated triterpenoids which contain a leaving group in position 3 for the shale samples degradation of monoaromatic secohopanoids must be considered as an alternative pathway

petroleum generation and migration in coal seams of the carboniferous ruhr basin northwest germany a series of 64 coal and clastic rock samples of westphalian age was taken from five narrow 3 m depth intervals between 1200 and 1530 m depth and studied by geochemical and petrological methods maturity increases regularly with increasing depth as indicated by several maturity parameters the influence of organic facies is evident in the uppermost coal seam 0 70 rr where a hand picked vitrinite contains less total extract and less saturated long chain hydrocarbons than a directly adjacent sporinite rich coal extracts from deeper and more mature coals are less affected by facies changes probably due to enhanced petroleum redistribution in the seams total yield and gross composition of extracts in the deepest seam 0 92 rr which is directly overlain by sandstone seem to be influenced by the preferential expulsion of saturated hydrocarbons

a quantitative study of aromatic hydrocarbons in a natural maturity shale sequence the 3 methylphenanthrene retene ratio a pragmatic maturity parameter abstract the aim of this study is to illustrate the use of multivariate statistical methods in identifying potential maturity parameters a study of the quantitative aromatic hydrocarbon results from a natural maturity sequence through a thick 3000 m organic lean shale followed by multivariate statistical treatment of the data was performed the study series consists of low toc ca 0 5 wt and rock eval s2 generally below 1 mg hc g rock shales showing a continuous maturity increase from tmax values of 410 c to ca 490 c this trend is mirrored by a concomitant decrease in the hydrogen index from values of around 150 mg hc g toc to ca 40 mg hc g toc based on the production indices and gc ms analysis of the saturated hydrocarbon biomarkers no indications of migrated hydrocarbons or major facies variations were found in the studied samples in essence this shale sequence represents a near perfect natural maturity series the 3 methylphenanthrene retene ratio shows an exponential increase with maturity and is proposed as a very sensitive maturity indicator extending into the late oil window this maturity ratio has since been successfully applied to both source rock extract kerogen type iii ii iii and ii and oil studies

striking liptinitic bark remains peculiar to some late permian chinese coals abstract an unusual liptinite coal component has been reported in the chinese literature over the past sixty years it has been described as a maceral in the chinese national standard 1991 but it has not been named internationally in chinese literature it is called barkinite on the basis of its morphological features and because it is believed to have originated as bark tissue barkinite occurs in late permian marine influenced coals and is best represented in the changguang leping and shuicheng basins of southern china the material originates from plant periderm or the bark of higher plants however bark contains a variety of substances including resin and suberin which are recognised as the precursors of the resinite and suberinite macerals barkinite is distinguished by i its thickness individual pieces can be more than ten cells thick and several centimetres long and ii it fluoresces strongly at 0 6 vitrinite reflectance and loses its fluorescence at about 1 1 vitrinite reflectance the reporting of barkinite from only chinese coals may be due to its origin from lepidodendron and psaronius flora which was common in the northern hemisphere during the carboniferous but which was isolated to china by the late permian it is proposed that the remnant flora evolved into unique forms in china by the late permian lepidodendron and psaronius remains coupled with a strongly marine influenced peat forming environment have given rise to barkinite and to its restricted distribution

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

aliphatic and aromatic biomarkers from gondwanan sediments of late ordovician to early devonian age an early terrestrialization approach abstract twenty one core samples of late ordovician to early devonian age from sections in southern tunisia north african platform gondwana and containing marine and terrestrial organic matter with microbial input were investigated to link the aliphatic and aromatic hydrocarbon distributions with the terrestrial and marine palynomorph content e g acritarchs prasinophytes chitinozoans cryptospores and trilete spores in addition to several biomarkers of algal bacterial origin long chain n alkanes that might be derived from land plants as well as the terrestrial diterpane norabietane were found several land plant derived biomarkers such as retene cadalene simonellite tetrahydroretene and c19 isohexylalkyl naphthalene were observed in the aromatic fractions while these terrestrial biomarkers could be clearly recognized in the middle silurian lower devonian samples their presence in the upper ordovician lower silurian sediments is more doubtful because of much lower relative abundances the land plant biomarkers show a fairly good correlation with the occurrence and abundance of cryptospores and trilete spores derived from bryophytes and tracheophytes which covered the emerged areas around the ghadamis basin during the silurian and devonian the early tracheophytes e g cooksonia lycophytes and zosterophylls are therefore suggested as a new terrestrial source for most of the saturated and aromatic biomarkers found in sediments of middle silurian to early devonian age

trimethylnaphthalenes in crude oils and sediments effects of source and maturity abstract three sedimentary sequences and a number of crude oils have been analysed for trimethylnaphthalenes tmns using gas chromatography the sediments were found to contain enhanced relative abundances of 1 2 5 tmn and 1 2 7 tmn in samples of cretaceous age and younger this was especially pronounced in lower maturity sediments containing type iii organic matter older samples containing type iii organic matter were found to contain enhanced relative abundances of 1 2 5 tmn and lower relative abundances of 1 2 7 tmn 1 2 7 tmn appears to be derived directly from the structural degradation of oleanane type triterpenoids present in angiosperms and as such is proposed as a marker for this class of plant and indirectly therefore also for samples deposited since the early cretaceous the crude oils have been classified according to their trimethylnaphthalene compositions this classification enables crudes of higher plant origin to be identified and to be further classified according to whether the organic matter pre dated or post dated the evolution of angiosperms

geochemical significance of the aromatic hydrocarbon distribution in the bitumens of the puertollano oil shales spain the bituminous series of the puertollano basin consists of three oil shale beds named pa pb and pc from top to bottom in this work results from the study of the aromatic fractions of the bitumens are presented the gas chromatographic traces are dominated by phenanthrene derivatives associated with variable contributions of arborane fernane derivatives and benzohopanes and overall small amounts of chrysene derivatives and secohopanes the compounds can be considered as part of two sub groups the first one consists of those compounds derived from regular hopanes such as secohopanes benzohopanes fully aromatized hopanes and degradation products of hopanes such as alkylated chrysenes and naphthalenes the second group is composed of arborane fernane derivatives and their degradation products such as alkylated phenanthrenes and tetrahydrophenanthrenes both groups of compounds appear to be indicative of a strong bacterial input to the sedimentary organic matter

comparison of resinite related aromatic biomarker distributions in cretaceous tertiary coals from canada and germany a set of 13 cretaceous tertiary coals from western canadian coal deposits and two cretaneous coals from the southern part of the lower saxony basin of germany have been investigated using microscopial and organic geochemical methods the coals are in the ranl range of lignite to medium volatile bituminous 0 37 1 13 rr petrographically the coals are characterized by varying proportions in vitrinite inertinite and liptinite groups in most of the coals resinite constitutes the major liptinite component both of the german wealden coals are composed exclusively of conifer needles gc ms analyses indicate differences in the composition of resin related molecular biomarkers comparing samples from both deposits in the canadian coals of moderate rank 0 4 0 8 rr resin related napthalene derivatives are associated with tricyclic aromatic hydrocarbons such as retene abieta 6 8 11 13 tetraene simonellite and c5 phenanthrene samples higher in rank about 1 1 rr provide fully aromatized and partly desalkylated phenanthrene homologues generation of 1 methylphenanthrene from retene during maturation affects molecular rank parameters like mpr and mpi 1 additionally an intra seam homogenization of resin derived aromatic hydrocarbon is observed in comparison the german wealden coal extracts are dominated by bicyclic aromatic hydrocarbons and they are poor in tricyclic hydrocarbons analyses of hand picked macerals resinites and cutinites by thermodesorption coupled to gc ms indicate the presence of two potential sources for the naphthalene derivatives c4 tetralin is primarily associated with the resins of abietites linkii 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnapthhalene are probably derived from the fluorinite filling of the conifer needles

conodonts and radiolarians from pelagic cherts of the frasnian famennian boundary interval at bancheng guangxi china global recognition of the upper kellwasser event abstract the recognition of five standard conodont biozones and five radiolarian zones in the same set of samples from cherts within the frasnian famennian f f boundary interval at bancheng southeastern guangxi china allowed precise placement of the f f boundary and demonstrated the multi episodic pattern of the f f mass extinction frasnian pelagic radiolarian and conodont faunas had an acme in the lower palmatolepis linguiformis zone in the upper pa linguiformis zone until the level of the upper kellwasser extinction kw members of the radiolarian family ceratoikiscidae and of the conodont frasnian populations disappeared above the kw in the lower palmatolepis triangularis zone new populations of the conodont pa triangularis gradually appeared and the survivor radiolarian genus trilonche gradually re appeared both blooming in the lower part of the middle pa triangularis zone the nehden extinction nd in the uppermost middle pa triangularis zone interrupted the recovery of the conodont and radiolarian faunas but above this level the conodont species became more numerous and the post extinction radiolarian faunas including entactiniidae recovered gradually

aromatic biomarkers as indicators of source depositional environment maturity and secondary migration in the oils of cambay basin india abstract aromatic biomarkers have been analysed for source depositional environment maturity and secondary migration in crude oils from different formations of paleocene to eocene age in the ahmedabad mehsana block of north cambay basin and the broach block of south cambay basin north cambay basin oils are characterized by a high abundance of 1 2 5 and 1 2 7 trimethylnaphthalenes tmn and low to medium ratio of dibenzothiophene phenanthrene and low ratio of pristane phytane indicates that these oils have been derived from a source containing predominantly higher plants and that the organic matter was deposited in restricted marine or lacustrine environments in anoxic to suboxic conditions the relative abundance of 1 2 7 tmn suggests that it was derived from the structural degradation of oleanane type triterpenoids present in angiosperms south cambay basin oils are less abundant in 1 2 5 and 1 2 7 tmns and low ratio of dibenzothiophene phenanthrene and high ratio of pristane phytane indicating that the oils were derived from higher plant source organic matter deposited under marine or fluvial deltaic environment in oxic conditions maturity sensitive ratios based on phenanthrene naphthalene dibenzothiophene and their alkyl substituted isomers have been used to calculate the equivalent vitrinite reflectance these parameters indicate a wide range of thermal maturity of the oils ranging from 0 60 to 0 93 vrc methylphenanthrene index and methyldibenzothiophene ratios indicate that the maturity of north and south cambay basin oils are different the north cambay basin oils are less mature than south cambay basin oils pyrrolic nitrogen distribution indicates that the alkylated carbazoles and benzocarbazoles are more abundant in south cambay basin oils as compared to north cambay basin oils these data indicate that north cambay basin oils are less migrated compared to south cambay basin oils this systematic investigation of the aromatic biomarkers in oils of cambay basin has resulted in a new generation migration and entrapment model that has led to the development of new exploration leads

facies and geochemistry across the early middle frasnian transition late devonian on south china carbonate shelf comparison with the polish reference succession abstract dongcun and longmen are two important reference sections for the study of the frasnian carbonate platform of guangxi southern south china at the dongcun section conodonts recovered in the present study provide a robust biostratigraphic framework for the lower middle frasnian interval the studied interval uppermost givetian to middle frasnian basal palmatolepis hassi zone is characterized by repeated shallower and deeper water deposits but the cyclic depositional trend was mainly deepening upward carbon isotopic investigation of bulk samples recognizes a major four step perturbation across the lower middle frasnian boundary which is also evident in the holy cross mountains poland the pattern is reinforced by correlative organic carbon isotopic secular trends from the reference polish sections a prominent long lasting increase in 13ccarb up to 4 5 event iii is evident in the palmatolepis punctata zone but is preceded and followed by rapid negative shifts events ii and iv respectively to ca 0 a weak incipient positive excursion event i is recognized in carbonate carbon only in the upper part of the palmatolepis transitans zone in chinese sections different background isotopic values indicate decoupled isotopically dissimilar hydrothermally affected and mostly oxygenated water masses over the carbonate shelf as shown by trace and rare earth elements the shallower water upslope diagenetically unaltered dongcun succession reveals lighter carbon isotopic ratios on the order of 2 while the less densely sampled and less certainly dated mostly muddy siliceous longmen downslope succession shows 13ccarb levels similar to those recorded worldwide the onset of the bipartite event iii is marked by 13c enrichment of 4 3 at dongcun event iv a light carbon excursion is especially well recorded in the shallow water facies by a 2 5 negative shift the event i excursion in the transitans zone is obscured as in some polish successions but is probably recorded in organic carbon trends slight differences in timing and magnitude of the 13ccarb oscillations may originate from geochemical decoupling between the open ocean and the tectonically active morphologically differentiated epeiric basins nevertheless a global extent for this major punctata event is clear from the similar biogeochemical signals recorded on the distantly separated south laurussian and south china shelves