effect of maturity on 13c12c ratios of individual compounds in north sea oils abstract carbon isotope variations in individual compounds are reported for north sea oils of variable thermal maturity using the pristane phytane ratio of the oils as an indication of source facies variation and molecular maturity ratios to determine maturity it is possible to differentiate the two effects in these samples maturity accounts for between 50 and 90 of the observed isotopic variation all values becoming heavier with increasing maturity typically by between 2 and 3 however source differences are also apparent with a terrestrially influenced source possibly the heather formation contributing material to the kimmeridge clay sourced oils the heather contribution is isotopically heavier than the kimmeridge oil for most compounds but is isotopically lighter for the isoprenoid hydrocarbons and some other branched compounds it is also more important for lower molecular weight hydrocarbons than for higher homologues

gas condensate migration and oil fractionation in deltaic systems abstract the term evaporative fractionation is proposed to describe several phenomena involved in the secondary alteration of reservoired oil firstly it is suggested that oil is frequently partially vaporized in the reservoir secondly that gas bearing substantial portions of the oil in solution is conducted along faults to form independent gas condensate accumulations thirdly that residual oils formed in this fashion bear internal evidence of fractionation in addition to the conspicuous loss of light ends there is an increase in the content of light aromatic and naphthenic hydrocarbons relative to paraffins in the residual oil evaporative fractionation effects are recognized for the first time in the distillation and physical property data of us bureau of mines routine method oil analyses fractionation effects are postulated to be the cause of sigmoid as opposed to normal curvilinear aromatic profiles the effects of evaporative fractionation are widespread in oils throughout the united states they are evident in approximately 75 of oils in the gulf coast region and in a large proportion of the gas condensate accumulations the process is a major and apparently unrecognized means of petroleum alteration and of generation of gas condensates experimental evidence shows that partial vaporization results in enhanced levels of light aromatic hydrocarbons in residual oils oil samples were partially vaporized in excess methane at elevated pressure and temperature followed by removal of the vapour the gas chromatographic features of many gulf coast oils were reproduced various levels of light end depletion and enhancement of aromaticity were brought about

alexander the great s tombolos at tyre and alexandria eastern mediterranean tyre and alexandria s coastlines are today characterised by wave dominated tombolos peculiar sand isthmuses that link former islands to the adjacent continent paradoxically despite a long history of inquiry into spit and barrier formation understanding of the dynamics and sedimentary history of tombolos over the holocene timescale is poor at tyre and alexandria we demonstrate that these rare coastal features are the heritage of a long history of natural morphodynamic forcing and human impacts in 332 bc following a protracted seven month siege of the city alexander the great s engineers cleverly exploited a shallow sublittoral sand bank to seize the island fortress tyre s causeway served as a prototype for alexandria s heptastadium built a few months later we report stratigraphic and geomorphological data from the two sand spits proposing a chronostratigraphic model of tombolo evolution

migration induced compositional changes in oils and condensates of a single field thirty one oils and condensates from the vermilion 39 field offshore louisiana u s gulf coast are examined using techniques of elemental isotopic and molecular geochemistry in an effort to determine the causes of compositional differences among them compositional variability in elemental concentration carbon isotope ratios and molecular distributions suggests that at least two sub groups occur in the sample set the sub groups are characterized by differences in n c 15 content relative to n c 15 pristane phytane ratio 13 c sulfur and nitrogen concentration and s n ratio although the separation into these two sub groups is superficially indicative of distinct sources and or variable levels of thermal maturity interpretation of the data set as a whole indicates that source influences maturity differences and biodegradation do not control observed variations in composition reliable source e g r c 27 29 sterane distribution and maturity e g 20s 20s 20r parameters provide clear evidence of a common source and constant maturity level for all 31 oils condensates the remaining geochemical differences including various molecular pristane phytane isotopic 13 c oil and elemental s n parameters correlate with the extent of migration fractionation that each sample has undergone as measured by the relative amount of n c 15 in each sample the migration fractionation process in the vermilion 39 field is facilitated by fault initiated pressure releases within reservoirs that originally contained full range crudes vertical migration of the released saturated hydrocarbon gases has led to a concentration of lighter components in the most fractionated samples this geochemical interpretation is supported by geologic data inasmuch as the extent of fractionation is least in the deepest samples and greatest in the shallowest samples the results presented here indicate the potential for misinterpretation of geochemical parameters previously considered to be influenced solely by source influence or thermal maturity

geochemical characterization of selected western canada oils by c5 c8 compound specific isotope correlation csic abstract forty two oils condensates from the western canada sedimentary basin wcsb ranging in reservoir age from devonian to cretaceous are compared using the stable carbon isotopic ratio of individual hydrocarbons in the gasoline range fraction c 5 c 8 of these oils continuous flow isotope ratio mass spectrometry cf irms using a modified solid dilution purge and trap inletting system can provide reproducible isotopic ratios for the ca 26 dominant n iso and cyclo alkanes and aromatics in the gasoline range the resulting isotopic signatures or gasoline isotopograms for oils condensates provide a diagnostic geochemical technique for oil oil and oil source correlations in many instances the non straight chained hydrocarbons are more diagnostic than n alkanes hierarchical cluster analysis provides a non subjective approach to the treatment of individual isotopic information this study confirms that oils from similar or the same sources produce isotopic signatures that are highly correlated clear carbon isotopic relationships between individual hydrocarbon compounds in the oils suggest a steady state kinetic relationship for the generation of oil and gas as opposed to a thermodynamic equilibrium relationship this mechanism explains the consistent shift in isotopic ratios between similar compounds such as the methylalkanes and dimethylalkanes

highly isotopically depleted isoprenoids molecular markers for ancient methane venting abstract we propose that organic compounds found in a miocene limestone from marmorito northern italy are source markers for organic matter present in ancient methane vent systems cold seeps the limestone contains high concentrations of the tail to tail linked acyclic c20 isoprenoid 2 6 11 15 tetramethylhexadecane crocetane a c25 homolog 2 6 10 15 19 pentamethylicosane pme and a distinctive glycerol ether lipid containing 3 7 11 15 tetramethylhexadecyl phytanyl moieties the chemical structures of these biomarkers indicate a common origin from archaea their extremely 13c depleted isotope compositions 13c 108 to 115 6 pdb suggest that the respective archaea have directly or indirectly introduced isotopically depleted methane derived carbon into their biomass we postulate that a second major cluster of biomarkers showing heavier isotope values 13c 88 is derived from sulfate reducing bacteria srb the observed biomarkers sustain the idea that methanogenic bacteria in a syntrophic community with srb are responsible for the anaerobic oxidation of methane in marine sediments marmorito may thus represent a conceivable ancient scenario for methane consumption performed by a defined two membered bacterial consortium 1 archaea that perform reversed methanogenesis by oxidizing methane and producing co2 and h2 and 2 srb that consume the resulting h2 furthermore the respective organic molecules are unlike other compounds tightly bound to the crystalline carbonate phase the marmorito carbonates can thus be regarded as cold seep microbialites rather than mere authigenic carbonates

worldwide initiation of holocene marine deltas by deceleration of sea level rise radiocarbon dated deltaic sequences of holocene age from different parts of the world began to accumulate within a restricted time range from about 8500 to 6500 years ago evaluation of major delta processes indicates that deceleration in sea level rise was the key factor in holocene delta formation within many deltas there is as much as a 2000 year age range between basal deposits in seaward and landward cores this age difference records the progressive landward migration of near mean sea level depositional environments during the lower to mid holocene establishment of a chronostratigraphic framework for holocene delta development provides a fundamental global baseline for distinguishing sea level change from vertical land motion by tectonism and isostasy and for evaluating rates of future marine incursion into low lying deltas

petroleum source in the tazhong uplift tarim basin new insights from geochemical and fluid inclusion data abstract a total of 108 drill stem test dst crude oil samples and 10 reservoir fluid inclusion samples were investigated geochemically to identify the characteristics and origin of the crude oil in the tazhong uplift tarim basin nw china results show that the majority of oils share typical biomarker characteristics from the middle upper ordovician o2 3 source rock and related crude oil features these features include a distinct v shape in the relative abundance of c27 c28 and c29 regular steranes and low abundances of dinosterane 24 norcholestanes triaromatic dinosteroids and gammacerane only a few oils display typical biomarker features indicating a cambrian lower ordovician o1 genetic affinity such as linear or anti l shape c27 c28 and c29 regular sterane distributions and relatively high concentrations of dinosterane 24 norcholestanes triaromatic dinosteroids and gammacerane it appears that most of the oils studied were derived from the o2 3 intervals as suggested by previous studies however the 13c values of individual n alkanes indicate that most of the crude oils in the tazhong uplift represent a mixture of two end member oils an o1 derived oil such as from well td2 or tz62 s and an o2 3 derived oil such as from well ym2 the data suggest that most of the oils in the uplift have a mixed origin and do not originated from the middle upper ordovician strata alone this conclusion is supported by data on the molecular composition of petroleum inclusions this new oil mixing model is critical for reconstructing the hydrocarbon formation and accumulation history for the region and may have important implications for further petroleum exploration in the tarim basin

geoscience of ancient mediterranean harbours abstract although much has been written on the subject of ancient mediterranean harbours the relatively new area of harbour geoarchaeology remains dispersed in the geoscience and archaeological literature over a decade of research has amassed rich and varied datasets of anthropogenically forced coastal evolution with a remarkable number of between site analogies this new research field also shows the rich potential of geoscience to reconcile important archaeological questions no single publication however has yet drawn on these geological patterns to yield a detailed overview suitable for geoscientists and environmental archaeologists the aim of this review article is to 1 discuss how ancient harbours have come to be preserved in the geological record 2 expound the basic principles and palaeoenvironmental tools underpinning ancient harbour geoarchaeology 3 outline some of the most significant research advances made and 4 discuss a new chrono stratigraphic model applicable to harbour sequences

evidence for biodegradation and evaporative fractionation in west sak kuparuk and prudhoe bay field areas north slope alaska abstract oils from the west sak kuparuk and prudhoe bay fields on the north slope of alaska display geochemical evidence for a complex petroleum filling history that includes multiple sources and alteration by evaporative fractionation and biodegradation source specific biomarkers in west sak oils indicate generation from the same source rocks in approximately the same proportions as prudhoe bay field oil consistent with the hypothesis that oil spilled from the deeper prudhoe accumulation and remigrated about 10 miles laterally and 5000 feet vertically into the west sak field west sak oils are moderately biodegraded but exhibit anomalously high concentrations of gasoline range saturate and aromatic compounds interpreted as a secondary gas condensate charge that arrived after biodegradation of the spilled prudhoe oil the shallowest west sak oils have less secondary gas condensate charge lower api gravities and reduced concentrations of methylcyclopentane benzene cyclohexane 3 methylhexane heptane methylcyclohexane and toluene relative to the deepest west sak zone a oils the carbon isotopic compositions of these c6 and c7 compounds in the shallowest west sak reservoirs are heavier than those of the deepest west sak oil reservoirs by up to 3 and the isotopic compositions of saturate compounds are altered more than those of aromatic compounds the heavier isotopic compositions of c6 and c7 compounds in the shallow west sak reservoirs are interpreted to result from a kinetic isotope shift caused by light biodegradation of the secondary gas condensate charge west sak field solution gas is also interpreted as biodegraded based upon its dryness 98 methane relatively high isobutane n butane ratio the presence of isotopically heavy carbon dioxide and isotopically light methane and propane that is isotopically heavier than either ethane or butane the isotopic compositions of methane and carbon dioxide in west sak gas suggest that biogenic methane was generated during co2 reduction under anaerobic conditions the isotopic compositions of c6 and c7 compounds in the deepest least biodegraded west sak oils are nearly identical to those of the underlying oils from the kuparuk field but differ from the prudhoe bay field oils the kuparuk field is therefore postulated as the source of the secondary gas condensate charge observed in oils from the west sak field ratios of toluene heptane and heptane methylcyclohexane in kuparuk oils provide independent evidence for loss of gas and condensate from the kuparuk reservoir by the process of evaporative fractionation and the oils subjected to the most evaporative fractionation are isotopically heavier in the c6 c7 range the isotopic compositions of west sak zone a c6 and c7 hydrocarbons suggest that a slight 0 8 isotopic fractionation resulted from evaporative fractionation of the gas condensate charge from the kuparuk field oil accumulation north northeast striking faults that connect the kuparuk and west sak reservoirs provide a potential migration pathway for the secondary gas condensate charge through 3000 feet of intervening shale this model of west sak oil biodegradation subsequent secondary gas condensate charge and further biodegradation has implications for development of north slope west sak oil reserves because heavily biodegraded west sak oils that lack a secondary gas condensate charge may be too viscous to develop by conventional waterflooding methods

are the n alkane carbon isotopic profiles of south australian coastal asphaltites indicative of their extent of weathering abstract asphaltic bitumen asphaltite found on the ocean beaches of south australia is considered to be a product of an adjacent but as yet unlocated submarine oil seep four large asphaltites recently stranded on three different beaches were sub sampled n 5 6 samples were analysed to determine if their n alkane 13c profiles displayed systematic variation along a transect from the centre to the outer rim of the specimen previously reported 13c enrichment in n alkanes isolated from the outer portions of similar archival asphaltites was attributed to weathering with one notable exception these new specimens exhibited no unidirectional enrichment from interior fresh to exterior weathered although in every instance n alkanes in the intermediate and outermost sub samples were for the most part isotopically heavier than the same homologues in the central interior of the specimen to be a viable measure of the extent of weathering in a population of coastal asphaltites and hence also their relative exposure time in the ocean this analytical protocol requires the specimens to have remained physically intact during their transit from the parent seep to shore whether this requirement has been met is impossible to determine thereby limiting the effectiveness of the method to those specimens in which there is a consistent pattern of internal variation in their n alkane carbon isotope profiles

carbon and hydrogen stable isotope variations in kerogen during laboratory simulated thermal maturation carbon and hydrogen stable isotope measurements on sapropelic and humic kerogen isolated from laboratory heated sediments reveal several isotopic trends an initial depletion of 13c and d 2h or deuterium in kerogen isolated from the heated sapropelic sediment appears to be the result of isotopic heterogeneity interaction with soluble organic matter and or volatilization of a heat labile fraction of the protokerogen during the main isotopic trend the sapropelic kerogen becomes enriched in 13c and d by about 5 and 50 ppt parts per thousand respectively theoretical calculations based on a rayleigh fractionation process suggest that this trend is largely controlled by the generation of isotopically light methane directly from the ker gen this argument also applies to the main hydrogen isotopic trend for the humic kerogen which becomes enriched in d by about 90 ppt the main 13c trend for the humic kerogen however results in a maximum enrichment in 13c of only about 1 6 ppt and appears to be largely controlled by factors other than methane a final depletion trend in 13c and d occurs for the sapropelic kerogen at very high temperatures this may be due to a reduced isotopic fractionation at higher temperatures or to the indirect generation of methane from kerogen through a liquid intermediate which is subsequently coked to pyrobitumen

effect of maturation on the indigenous δd signatures of individual hydrocarbons in sediments and crude oils from the perth basin western australia abstract we measured the stable hydrogen isotopic composition d of selected aliphatic hydrocarbons in nine sediments of various maturity and two crude oils all from the northern perth basin on shore western australia the sediments and crude oils are from the lower triassic hovea member sapropelic interval of the kockatea shale the n alkanes pristane and phytane from two immature sediments have d values that represent the expected isotopic compositions of their precursors phytane is enriched in deuterium d relative to pristane in all sediment extracts and crude oils this is attributed to either different sources or to different isotopic effects during their derivation from phytol with increasing maturity pristane and phytane become enriched in d while the n alkanes generally remain at a constant isotopic composition a more rapid enrichment of d in isoprenoids relative to n alkanes with increasing maturity suggests that hydrogen isotopic exchange is occurring via a carbocation mechanism the phytane diastereomer ratio for each of the sediments correlates linearly with the progressive enrichment of d in phytane and therefore maturity suggesting that significant hydrogen exchange occurs at the chiral carbons of phytane the d values of pristane and phytane from the crude oils are similar or more positive relative to the d values of the n alkanes the average d values of pristane and phytane for the sediments correlate well with equivalent vitrinite reflectance values as does the conventional biomarker maturity parameter t s t m indicating that d values may be useful for establishing maturity over a wider range than conventional biomarker parameters the results provide further evidence that care must be taken not to over interpret d values of sedimentary hydrocarbons in samples of high thermal maturity

use of hydrogen and carbon stable isotopes characterizing oils from the potiguar basin onshore northeastern brazil hydrogen and carbon isotopic abundances were measured in representative samples of marine evaporitic lacustrine and mixed oils from the onshore potiguar basin the isotopic data together with chemical compositions and geological information were used to investigate relationships among ddoil and d13coil and source thermal maturity biodegradation mixing and the distance of secondary migration of these oils the marine evaporitic oils are depleted in deuterium 135 to 114 and the lacustrine oils are enriched 101 to 88 values of dd for mixed oils are intermediate 113 to 104 between those of marine evaporitic and lacustrine oils showing that ddoil is a reliable tool to identify oils that differ genetically values of ddoil were not directly related to thermal maturation biodegradation or distance of the secondary migration hydrogen isotopic compositions of the oils can be related mainly to the ddwater in the paleoenvironments in which the primary producers lived therefore ddoil values can provide rough estimates of ddwater in the depositional environments of the source rocks and consequently may provide evidence about paleoclimatic conditions at the site marine evaporitic oils are enriched in 13c 26 5 to 25 7 and lacustrine oils are depleted 33 6 to 30 2 in 13c relative contributions of marine evaporitic and lacustrine sources to mixed oils thus can be calculated independently from carbon or hydrogen isotopic mixing models when these calculations are done independently the mixed oils separate into two families and a previously unrecognized component possibly associated with environments that formed during the lacustrine to marine transition is revealed the investigation thus demonstrates the superior resolving power of two element mixing systematics

the ancient harbour parasequence anthropogenic forcing of the stratigraphic highstand record abstract unique chronostratigraphic similarities are observed in recent geoscience literature on ancient mediterranean harbours from these empirical port data a clear pattern of millennial anthropogenic forcing marked by a fining up sequence can be discerned in coastal stratigraphy the stratigraphic peculiarity of this artificial or human modified parasequence leads us to define a new working model the ancient harbour parasequence

reply to comment on magnetization of the oceanic crust thermoremanent magnetization or chemical remanent magnetization by c a raymond and j l labrecque

active thrusting offshore mount lebanon source of the tsunamigenic a d 551 beirut tripoli earthquake on 9 july a d 551 a large earthquake followed by a tsunami destroyed most of the coastal cities of phoenicia modern day lebanon tripoli is reported to have drowned and berytus beirut did not recover for nearly 1300 yr afterwards geophysical data from the shalimar survey unveil the source of this event which may have had a moment magnitude mw of 7 5 and was arguably one of the most devastating historical submarine earthquakes in the eastern mediterranean rupture of the offshore hitherto unknown 100 150 km long active east dipping mount lebanon thrust deep towed sonar swaths along the base of prominent bathymetric escarpments reveal fresh west facing seismic scarps that cut the sediment smoothed seafloor the mount lebanon thrust trace comes closest 8 km to the coast between beirut and enfeh where as 13 14c calibrated ages indicate a shoreline fringing vermetid bench suddenly emerged by 80 cm in the sixth century a d at tabarja the regular vertical separation 1 m of higher fossil benches suggests uplift by three more earthquakes of comparable size since the holocene sea level reached a maximum ca 7 6 ka implying a 1500 1750 yr recurrence time unabated thrusting on the mount lebanon thrust likely drove the growth of mount lebanon since the late miocene

petroleum source maturity alteration and mixing in the southwestern barents sea new insights from geochemical and isotope data the hammerfest basin hb is an important area for petroleum exploration in the southwestern norwegian barents sea this contribution is aimed to characterize oils and condensates hosted in triassic and jurassic reservoirs establish genetic relationships and to assess maturity mixing and petroleum alteration processes the research was based on geochemical as well as bulk and compound specific stable carbon and hydrogen isotope analyses of oil and condensate samples from all major fields and discoveries in the hb including extracts from jurassic and triassic source rocks interpretations of light hydrocarbon composition and isotope data clearly identify four main petroleum groups affected by microbial degradation water washing evaporative fractionation and high thermal maturity level based on polycyclic aromatic hydrocarbons pahs marine and higher plant derived biomarkers and carbon isotopic composition 13c of individual petroleum hydrocarbons four petroleum families i iv are recognized in the hb and a distinction can be made among oils and condensates from different stratigraphic levels and sectors of the basin most oils and condensates from the hb consist of mixtures with small maturity variations however oils from middle triassic reservoirs in the goliat field showed larger maturity variations according to biomarker pah and light hydrocarbon maturity ratios in the hb geochemical and isotopic data allowed unraveling mixtures of hydrocarbons derived mainly from jurassic triassic and paleozoic source rocks

compound specific isotope analysis as a tool for characterizing mixed oils an example from the west of shetlands area abstract the origin of an oil accumulation can be difficult to establish when the oil is a mixture from multiple sources or when multiple episodes of charging are involved in this study oils from the clair field west of shetland islands which are mixtures of nonbiodegraded oil added to biodegraded oil are characterized by comparing the carbon isotope ratios of the gasoline range hydrocarbons grh of the oil to the grh released from the pyrolysis of the asphaltenes in the oil this comparison allows characterization of the source of the first versus the second pulse of oil into the reservoir information useful in assessing the source potential of the basin

constraints on the quantitative assessment of in reservoir biodegradation using compound specific stable carbon isotopes with the increasing interest and technical availability of compound specific isotope analysis this analytical method has successfully been applied to characterise microbial degradation processes of hydrocarbons and in petroleum geochemistry for quantification of the biodegradation processes isotopic fractionation is evaluated using the rayleigh equation the rayleigh model can also be successfully used to quantify biodegradation of light hydrocarbons in petroleum reservoirs we demonstrate here the reliability of the rayleigh approach for evaluation of crude oil biodegradation in two different petroleum systems and discuss the geochemical implications for processes such as charging and mixing and the limitations of the method

unraveling petroleum mixtures from the south viking graben north sea a study based on δ13c of individual hydrocarbons and molecular data abstract mixtures of compositionally different petroleum occur in the norwegian north sea one of the world s major oil producing regions the objective of the present contribution was to appraise the source maturity in reservoir mixing and alteration processes in a set of condensate and oil samples covering the main producing areas in the south viking graben svg furthermore this study focused on unraveling complex mixtures of petroleum and quantifying mixing ratios of hydrocarbons generated from jurassic source rocks the present research was based on a multiparameter approach that comprised the molecular composition of light hydrocarbons and heterocyclic and polycyclic aromatic compounds as well as the 13c of individual hydrocarbons in oils condensates and upper and middle jurassic source rock extracts from the svg according to the relative contribution of oils from type iii kerogen rich source rocks seven populations a g of mixed petroleum were identified by combining source related ratios of heterocyclic and non heterocyclic aromatic hydrocarbons and 13c values of n alkanes pristane pr and phytane ph the heterocyclic and polycyclic aromatic hydrocarbons provided a useful means to discriminate mixed hydrocarbons from source rocks of distinct organic matter type depositional environment and lithology in the svg the 13c enrichments of c10 c14 n alkanes and pr and ph were good indicators of the scale of the terrigenous source contribution and allowed quantitative determination of the proportions of jurassic source contributions enriched in type ii and type iii kerogens in complex petroleum mixtures from the southern part of the svg

correlation between hydrogen isotope ratios of lipid biomarkers and sediment maturity abstract we investigated the influence of thermal maturity on the hydrogen isotope ratios of sedimentary hydrocarbons to prove that the isotope ratio of hydrocarbons mirrors paleoclimate signatures d values from n alkanes and acyclic isoprenoids of two sediment sections kupferschiefer ks 258 ma and posidonienschiefer ps 184 ma with different maturation history were investigated both covered thermal maturity from 0 48 to 1 3 rc vitrinite reflectance and reflectance calculated from mpi1 sediment burial up to 4500 m caused thermal maturation of organic matter in the ks horizon from the early zechstein basin of poland whereas contact metamorphic thermal maturation originated in the early toarcian ps posidonienschiefer of the north german vlotho massif the d values of the extracted n alkanes positively correlate with thermal maturity in the ks y 56 mpi1 x 160 vsmow and in the ps y 104 mpi1 x 200 vsmow the d values of isoprenoids i e pristane phytane were even more enriched with increasing maturity y 179 mpi1 x 341 vsmow in the ks y 300 mpi1 x 415 vsmow in ps these results explain why isotope ratios of n alkanes and isoprenoids in mature sediments are generally enriched in d and do not have the expected isotopic difference between n alkanes and isoprenoids of 190 moreover the correlation between sediment maturity parameters and d values suggests that after correction the d values of n alkanes can be used to reconstruct climate and environment in the geological past

a 3 800 million year isotopic record of life from carbon in sedimentary rocks an increased ratio of 12c to 13c an indicator of the principal carbon fixing reaction of photosynthesis is found in sedimentary organic matter dating back to almost four thousand million years ago a sign of prolific microbial life not long after the earth s formation partial biological control of the terrestrial carbon cycle must have been established very early and was in full operation when the oldest sediments were formed

oil source rock correlations limitations and recommendations a rigorous defensible and causal oil source rock correlation definitively ties an individual source rock sample to an individual crude oil using genetically based internally consistent parameter matches such a correlation is a relationship established between the two components which is consistent with all known chemical geochemical and geological information and meets three criteria a the relationship must be causal the oil must arise at least in part from the specified source rock s b chemical data used in the correlation must be comparable the elemental molecular and isotopic data derived from the source rock must be of the same type as that derived from the oil and c all available geological data must be supportive clear geological evidence must exist which allows the proposed source rock to have sourced the oil the three points of this definition are satisfied and the correlation is successful if we solve one analytical and three geological problems natural extraction of crude oil from its source rock i e expulsion differs mechanically and temporally from laboratory extraction leading to a correlation problem referred to as extraction differences and representing the single greatest analytical uncertainty in correlation efforts geologically three aspects confound oil source correlations occurrence of multiple source units and or source units at differing maturity levels lateral and vertical depositional variations in source unit s organic matter and lateral and vertical variation in reservoir unit s organic matter these concerns are overcome by taking five actions for each oil source correlation effort 1 select representative samples using statistically defensible methods 2 establish the inherent compositional variability laterally and temporally due to depositional and maturation processes in each prospective source unit 3 assess the extent of migration induced changes in oil composition including post migration changes such as in reservoir alteration 4 support each correlation with migration histories derived from 4d models 5 iterate correlation results with new data gathered from ongoing exploration efforts these five actions will a allow correlation success to be measured more objectively b establish risking parameters for direct use in basin assessment and c provide baseline criteria for use in assessing the reliability of oil source rock correlations although these approaches will improve conventional oil source rock correlation efforts ultimately they may not be needed if inversion methods become more reliable the ability to invert compositional data for crude oil i e predict the age lithology maturity and other characteristics of a source rock solely through chemical analysis of its expelled oil could eventually result in successful oil source rock correlations in which source rock analysis for oil source rock correlation purposes is less critical

the effect of source and maturity on the stable isotopic compositions of individual hydrocarbons in sediments and crude oils from the vulcan sub basin timor sea northern australia abstract recent work has demonstrated the effect of maturation on the stable hydrogen isotopic compositions d of individual sedimentary hydrocarbons n alkanes pristane and phytane in a series of marine source rocks from the perth basin western australia there was an enrichment in deuterium d in the hydrocarbons with increasing maturity attributed to isotopic exchange associated with thermal maturation an initial large 115 biologically derived difference between the d values of n alkanes and isoprenoids gradually decreased as pristane and phytane became enriched in d while the n alkanes generally remained at constant isotopic composition this work has now been extended to include a series of late jurassic sediments from the lower vulcan formation of the vulcan sub basin timor sea northern australia where the d values of n alkanes and isoprenoids show similar trends to those observed for the perth basin the enrichment in d in isoprenoids correlates strongly with traditional maturity parameters and is shown to be related to the epimerisation of pristane and phytane pristane and phytane extracted from a post mature paqualin 1 sediment are significantly enriched in d relative to the n alkanes indicating that d enrichment persists at very high maturity more so for regular isoprenoids than n alkanes this supports the notion that hydrogen h d exchange causes the observed shift in d values and not free radical hydrogen transfer a mechanism is proposed which can account for both h d exchange and epimerisation of pristane and phytane in the sedimentary environment pristane is enriched in d relative to phytane throughout the vulcan sub basin sequences attributed to a lower relative algal input to the isoprenoids and indicating that they exchange hydrogen at similar rates during maturation crude oils and condensates from the sub basin were also analysed to evaluate their source and thermal maturity and the results complement previous molecular and stable carbon isotopic analysis the d values of n alkanes and regular isoprenoids largely support the previous classification of vulcan sub basin crude oils and condensates into two groups group a having a marine source affinity and group b a terrigenous source affinity some oils and condensates are suggested to be a mixture of sources a and b or a and other as yet unknown sources tenacious 1 crude oil formerly a group a oil contains n alkanes with more positive d values than other group a oils and is suggested to have been mixed with another source of more mature hydrocarbons the group a crude oils and condensates show an upward inflection in the n alkane d profile from n c 11 to n c 15 which is suggested to represent an addition of d enriched lower molecular weight n alkanes from a more mature wet gas condensate to an initial oil charge the small differences between the d values of the n alkanes and regular isoprenoids in the crude oils and condensates indicate that significant h d exchange has taken place implying that the samples were generated from mature source rocks

recent advances in petroleum isotope geochemistry abstract organic matter is isotopically heterogeneous lipids tend to be depleted in the heavy carbon and hydrogen isotopes as compared to carbohydrates and lignite the c and h isotopic composition of kerogens is determined by many factors such as environmental conditions during formation and deposition and variability of sources of organic matter stable isotope concentrations in mature kerogens are not significantly altered during maturation and hence reflect the variability of the organic matter during deposition isotope variations in kerogens therefore reflect to some extent the paleogeographic situation and can be used for paleoreconstruction a basin facies with anoxia and a marginal facies with detrital input can be differentiated isotopically in the toarcian of central europe coals are isotopically heterogeneous due to different isotopic composition of macerals inertinite and vitrinite tends to be enriched in deuterium as compared to exinite also boghead coals tend to be depleted in dueterium which possibly reflects various lipid contents of respective precursor materials petroleums can be genetically classified through the patterns of covariance of their compound classes carbonate and shale sourced petroleums may be additionally differentiated through their deuterium content the general world wide applicability of such genetic differentiations needs still to be proved carbon and hydrogen isotope variations in methane are genetically controlled bacterial methane in freshwater environments is characteristically depleted in deuterium even complex origins of natural gases can be unraveled using compositional and isotopic variations new analytical developments led to the application of carbon isotope analyses of gaseous hydrocarbons desorbed from sediments for geochemical surface exploration a discussion reveals that processes such as isotope effects during degassing and bacterial oxidation as well as indigenous formation of hydrocarbons may completely obscure the results

seismic evidence for neogene and active shortening offshore of lebanon shalimar cruise 1 lebanon located on a 160 km long transpressional bend of the left lateral levant dead sea fault system lfs has been the site of infrequent but large earthquakes including one submarine tsunamigenic event the main objective of the shalimar marine survey was to characterize and map active deformation offshore of lebanon using a range of geophysical techniques particularly seismic reflection profiling the cruise results clearly establish the presence of young submarine thrust faults and folds and clarify the structure of this part of the levant margin a submarine fold belt bounded by thrusts and lateral ramps and extending up to 30 km from the shoreline is interpreted as the foreland thrust system of the actively growing mount lebanon range there is no large fault extending into the levant basin toward cyprus which indicates that thrusting only absorbs local transpression resulting from the lebanese restraining bend both the miocene and plio quaternary sedimentary sequences are affected by shortening with landward dipping blind thrusts and associated growth strata the presence of the messinian evaporites creates complex deformation patterns including normal faults due both to folding accommodation and to gravity spreading all well imaged in the seismic reflection profiles because the evaporite layer acts as a decollement level shortening extends farther out seaward through a series of thrust imbricates or duplexes the strongest shortening observed between beirut and batroun decreases toward the south between saida and tyre north of tripoli the passive margin is not affected by neogene deformation and is well preserved we propose that since the miocene the northward propagating lfs interacted with margin structures inherited from the mesozoic rifting phase and was deviated along the more rigid oceanic crust flooring the levant basin a process which led to the formation of the lebanese restraining bend of the lfs and consequently to the offshore shortening we document here such coastal transpression has resulted in local 100 km inversion of the passive margin which might eventually evolve into a new subduction zone

molecular and isotopic compositions of bitumens in silurian tar sands from the tarim basin nw china characterizing biodegradation and hydrocarbon charging in an old composite basin abstract biodegradation and oil mixing in silurian sandstone reservoirs of the tarim basin one of the largest composite basins in china were investigated by analyzing the molecular characteristics and stable carbon isotopic signatures of low molecular weight lmw saturated hydrocarbons and high molecular weight hmw asphaltenes detection of 25 norhopanes and 17 nortricyclic terpanes in most silurian tar sands from the tabei uplift in the tarim basin suggests a much greater degree of biodegradation here than in the tazhong uplift this explains the relatively more abundant tricyclic terpanes gammacerane pregnane and diasteranes in tar sands from the tabei uplift than in those from the tazhong uplift hence care must be taken when assigning oil source correlations using biomarkers in tar sands because of the biodegradation and mixing of oils derived from multiple sources in such an old composite basin asphaltenes in the tar sands seem to be part of the oil charge before biodegradation depending on the relative anti biodegradation characteristics of asphaltenes the similarity in carbon isotopic signatures for asphaltenes and their pyrolysates and the consistent product distribution for flash pyrolysis and for regular steranes in asphaltene pyrolysates regardless of whether the tar sands were charged with fresh oil according to the relative distributions of regular steranes and the relatively abundant 1 2 3 4 tetramethylbenzene significantly enriched in 13 c the oil sources for asphaltenes in the tar sands might be related to lower paleozoic marine source rocks formed in euxinic conditions nevertheless the relatively low abundance of gammacerane and c 28 regular steranes observed in asphaltene pyrolysates and residual hydrocarbons within limited samples investigated in this work made a direct correlation of oils originally charged into silurian tar sands with those cambrian source rocks reported so far seem not to be possible comparison of carbon isotopic signatures of n alkanes in asphaltene pyrolysates with those of lmw saturated hydrocarbons is helpful in determining if the abundant n alkanes in tar sands are derived from fresh oil charges after biodegradation the limited carbon isotopic data for n alkanes in lmw saturated hydrocarbons from the tar sands can be used to classify oils charged after biodegradation in the composite basin into four distinct groups

geoarchaeology of beirut s ancient harbour phoenicia abstract this paper presents geoarchaeological results from the ancient harbour of beirut lebanon as at sidon knowledge of beirut s ancient tell has advanced significantly over the past decade thanks namely to redevelopment of the city centre and excavations centred on the modern port in spite of this research understanding of the city s coastal palaeoenvironments during antiquity is poor buried iron age harbourworks presently 300 m from the sea attest to pronounced coastal changes during the past 3000 years these processes have been significantly accentuated during the last two centuries by redevelopment of the port which remains in use some 5000 years after its foundation here we elucidate the coastal stratigraphy east and west of the bronze age tell to yield new insights into the evolution of the beirut seaboard in addition to the complex history of human environment interactions these chronostratigraphic data are subsequently used to 1 precisely locate the main anchorage haven during antiquity and 2 propose a chronology for its evolution

middle east coastal ecosystem response to middle to late holocene abrupt climate changes the holocene vegetation history of the northern coastal arabian peninsula is of long standing interest as this mediterranean semiarid arid region is known to be particularly sensitive to climatic changes detailed palynological data from an 800 cm alluvial sequence cored in the jableh plain in northwest syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby jabal an nusayriyah mountains for the period 2150 to 550 b c corresponding with the 4 2 to 3 9 and 3 5 to 2 5 cal kyr bp abrupt climate changes accs two large scale shifts to a more arid climate have been recorded these two accs had different impacts on the vegetation assemblages in coastal syria the 3 5 to 2 5 cal kyr bp acc is drier and lasted longer than the 4 2 to 3 9 cal kyr bp acc and is characterized by the development of a warm steppe pollen derived biome 1100 800 b c and a peak of hot desert pollen derived biome at 900 b c the 4 2 to 3 9 cal kyr bp acc is characterized by a xerophytic woods and shrubs pollen derived biome ca 2050 b c the impact of the 3 5 to 2 5 cal kyr bp acc on human occupation and cultural development is important along the syrian coast with the destruction of ugarit and the collapse of the ugarit kingdom at ca 1190 to 1185 b c

migration effects on the composition of hydrocarbon accumulations in the oml 67 70 areas of the niger delta systematic changes in gas oil ratios in the oml 67 70 area joint venture acreage of the niger delta nigeria illustrate the effects of hydrocarbon migration on the compositional changes observed in the accumulations over large depth intervals one interpretation is that the reservoirs are currently both filling and leaking hydrocarbons indicating that trap styles affect the migration pathways in this region of the niger delta the accumulations are more liquid prone with depth based on the bubble point of the fluids in the reservoir applying these results to regional exploration opportunities indicates that fluid contacts in the normally pressured section are controlled by leaking seals class iii traps the potential exists for pressure controlled filled to spill traps class ii traps in the overpressured section where a high quality seal impedes the vertical flux of hydrocarbon fluids although these conclusions apply to a specific portion of the niger delta combining the concept of trap style with compositional changes resulting from migration processes is useful in identifying new play concepts and opportunities in other regions of the world

the impact of severe biodegradation on the molecular and stable c h n s isotopic compositions of oils in the alberta basin canada abstract although the effects of biodegradation on the composition and physical properties of crude oil have been well studied effects of in reservoir petroleum biodegradation on molecular and isotopic compositions of crude oils are not yet clearly understood the alberta basin in western canada is one of the world s largest petroleum accumulations and constitutes an ideal example of a natural suite of sequentially biodegraded oils the basin hosts moderately to severely biodegraded petroleum regionally distributed and in single more or less continuous oil columns in this study a series of oil samples from the alberta heavy oil and oil sands provinces with varying degrees of biodegradation were analyzed to assess the impact of progressive biodegradation on the molecular and c h n and s isotopic compositions of oils the results of the molecular characterization of the hydrocarbon fraction of the studied oils show that the oils have suffered biodegradation levels from 2 to 10 toward the alberta saskatchewan border on the peters and moldowan scale of biodegradation abbreviated pm 2 to pm 10 and from tens to hundreds on the manco scale within single reservoirs increasing biodegradation was observed from top to bottom of the oil columns at all sites studied the whole oil stable isotopic compositions of the samples varied in the ranges 13 c 31 2 to 29 0 2 h 147 to 133 15 n 0 3 4 7 and 34 s 0 4 6 4 the maximum differences between values of samples within single oil columns were 13 c 1 4 2 h 7 15 n 1 7 and 34 s 1 0 regional variations in the isotopic compositions of oil samples from different wells averaged values from top to bottom were 1 2 for 13 c 12 for 2 h 4 1 for 15 n and 5 5 for 34 s and hence generally significantly larger variations were seen than variations observed within single oil columns especially for n and s it appears that even severe levels of biodegradation do not cause observable systematic variations in carbon nitrogen or sulfur isotope composition of whole oils this indicates that sulfur and nitrogen isotopic compositions may be used in very degraded oils as indicators for oil charge from different source rock facies

application of tetracyclic polyprenoids as indicators of input from fresh brackish water environments abstract c30 tetracyclic polyprenoids tpp are most prominently observed in samples derived from low salinity i e fresh to brackish lacustrine environments and are generally present in low levels in samples derived from saline i e marine and saline lacustrine environments a near shore facies of the chonta formation peru that has no marine palynomorphs but abundant chlorococcalean green algal nonmarine palynomorphs has high levels of tpp suggesting green algae or chlorophyta are a possible source for the tpp compounds the ratio between a c30 tpp compound and 27 norcholestanes is useful for assessing this nonmarine algal input moderate elevations of tpp above what is common in marine derived samples were found in ostensibly marine source rocks and oils from certain basins of western and northern south america middle magdalena colombia maracaibo venezuela and trinidad basins this is likely due to transport from the nonmarine to the marine environment because of an influx of fresh water into the near shore marine environment alternatively oils from these basins may have inputs from near shore shallow marine algae with chemistry similar to that found in lacustrine settings the tpp ratio in conjunction with other environmental indicators such as 4 methyl steranes or hopane sterane ratio is useful for differentiating marine and nonmarine influences in pre salt oils and source rocks of west africa the tpp ratio used with other environmental indicators gammacerane c29 steranes c30 steranes and age diagnostic biomarkers dinosteranes 4 methylsteranes can be useful in differentiating among nonmarine source facies for example in the turpan hami basin china permian saline lacustrine and jurassic lacustrine deltaic facies can be discriminated

crustal structure interpreted from magnetic anomalies this review discusses publications during the last quadrennium 1987 1990 that used aeromagnetic data marine magnetic data satellite magnetic data and rock magnetic and petrologic data to provide information on the sources of magnetic anomalies the publications reviewed reflect increased integration of rock magnetic property and petrologic studies with magnetic anomaly interpretation studies particularly in deep crustal magnetization exploration for hydrocarbons and inversion of marine magnetic anomalies interpretations of aeromagnetic data featuring image display techniques and using the horizontal gradient method for locating magnetization boundaries became standard

variation in the isotopic composition of single components in the c4 c20 fraction of oils and condensates abstract determination of the isotopic composition of individual compounds in the c4 c15 range has been difficult due to the lack of suitable instrumentation it has also been suggested that isotopic fractionation during storage might occur with the introduction of online gc irms an instrument is now available to test whether or not isotopic fractionation occurs during storage to test this two condensates were analysed using the gc irms method samples were taken for analysis at regular intervals during storage at elevated temperatures only small changes in isotopic composition were observed during evaporation with a slight enrichment in 13c in some compounds however the changes are so small that even prolonged storage times do not significantly affect the carbon isotopic composition of the compounds as long as there is enough material left for analysis two separate suites of samples one from the central graben the other from the viking graben were used to demonstrate the use of the technique in correlating oils and condensates this study shows that the oil condensates in the central graben are not sourced from a single source rock differing only in maturity as reported earlier but are sourced from various source facies where especially edda differs significantly from the others i e the compounds in edda are 1 2 0 heavier than the rest of the analysed samples in the central graben the analysed viking graben oils and condensates were divided into three groups based on this study

applications of petroleum geochemistry to exploration and reservoir management abstract petroleum geochemistry improves exploration efficiency by accounting for many of the variables that control the volumes of crude oil and natural gas available for entrapment including source rock distribution richness and quality thermal maturity and the timing of generation migration accumulation relative to trap formation it is most powerful when used with other disciplines such as seismic sequence stratigraphy and reservoir characterization four key technology milestones form the basis for most modern applications of geochemistry to exploration these are the concepts and applications of 1 petroleum systems and exploration risk 2 biomarkers stable isotopes and multivariate statistics for genetic oil oil and oil source rock correlation 3 calibrated three dimensional thermal and fluid flow modeling and 4 controls on petroleum composition by secondary processes petroleum geochemistry offers rapid low cost evaluation tools to aid in understanding development and production problems some technology milestones in reservoir geochemistry include 1 assessment of vertical and lateral fluid continuity 2 determination of proportions of commingled production from multiple zones and leaky casing 3 prediction of oil quality in reservoir zones and 4 prediction of gas oil and oil water contact locations as described in the conclusions future research will continue a trend toward predictive geochemistry examples of predictive tools that draw major research support include piston core surveys to assess deepwater petroleum systems prior to drilling and three dimensional basin modeling to predict the regional timing of generation migration and accumulation of petroleum among other research objectives models are needed to better predict the distribution and quality of petroleum in reservoirs

preservation of lipid hydrogen isotope ratios in miocene lacustrine sediments and plant fossils at clarkia northern idaho usa abstract we measured d h ratios of individual lipids isolated from plant fossils and water lain sediments from the miocene clarkia lacustrine deposit 15 20 ma in northern idaho usa in order to assess the preservation potential of lipid hydrogen isotope ratios distinct n alkyl lipid profiles in plant fossils platanus quercus salix and the sedimentary matrix demonstrate the high degree of lipid preservation as previously reported our data suggest that original hydrogen isotope ratios of carbon bound hydrogen in lipids may have been preserved after 15 20 million years of burial in the water lain lacustrine sediment because d values of individual lipids show large variations between different fossil genera and between fossils and sediments and hydrogen isotope values of fossil lipids differ by more than 123 from the associated sediment water these data are consistent with minimal isotopic exchange between carbon bound hydrogen in lipids and sediment water hydrogen our results validate the use of lipid hydrogen isotope ratios for paleoecological studies over an extended geological time period

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

ancient harbors and holocene morphogenesis of the ras ibn hani peninsula syria abstract ras ibn hani peninsula a wave dominated tombolo 800 1000 m on the syrian coast provides evidence for significant holocene changes that can be linked to geological inheritance rising post glacial sea level sediment supply and human impacts initial development of ras ibn hani s coastal system began 8000 years ago when shallow marine environments formed in a context of rising post glacial sea level following relative sea level stabilization 6000 cal yr bp beach facies trace the gradual formation of a wave dominated sandbank fronted by a 2300 500 m palaeo island whose environmental potentiality was attractive to bronze age societies a particularly rapid phase of tombolo accretion is observed after 3500 cal yr bp characterised by a two to fourfold increase in sedimentation rates this is consistent with i a pulse in sediment supply probably driven by bronze age iron age soil erosion in local catchments and ii positive feedback mechanisms linked to regionally attested neotectonics archaeological remains and radiocarbon datings confirm that the subaerial tombolo was probably in place by the late bronze age these data fit tightly with other eastern mediterranean tombolo systems suggesting that there is a great deal of predictability to their geology and stratigraphy at the regional scale

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

carbon and hydrogen isotopic compositions of n alkanes as a tool in petroleum exploration compound specific isotope analysis csia of individual organic compounds is a powerful but underutilized tool in petroleum exploration when integrated with other organic geochemical methodologies it can provide evidence of fluid histories including source maturity charge history and reservoir processes that can support field development planning and exploration efforts the purpose of this chapter is to provide a review of the methodologies used for generating carbon and hydrogen isotope data for mid and high molecular weight n alkanes we discuss the factors that control stable carbon and hydrogen isotope compositions of n alkanes and related compounds in sedimentary and petroleum systems and review current and future applications of this methodology for petroleum exploration we discuss basin specific case studies that demonstrate the usefulness of csia either when addressing particular aspects of petroleum exploration e g charge evaluation source rock oil correlation and investigation of maturity and in reservoir processes or when this technique is used to corroborate interpretations from integrated petroleum systems analysis providing unique insights which may not be revealed when using other methods csia of n alkanes and related n alkyl structures can provide independent data to strengthen petroleum systems concepts from generation and expulsion of fluids from source rock to charge history connectivity and in reservoir processes

geoarchaeology of sidon s ancient harbours phoenicia abstract geoarchaeological data from sidon s ancient harbour areas elucidate six evolutionary phases since the bronze age 1 at the time of sidon s foundation during the third millennium bc medium sand facies show the city s northern and southern pocket beaches to have served as proto harbours for middle to late bronze age societies 2 towards the end of the late bronze age and the early iron age expanding international trade prompted coastal populations into modifying these natural anchorages in sidon s northern harbour transition from shelly to fine grained sands is the earliest granulometric manifestation of human coastal modification the lee of zire island was also exploited as a deep water anchorage or outer harbour at this time 3 although localised sediments evoke developed port infrastructure during the phoenician and persian periods high resolution reconstruction of the northern harbour s iron age history is problematic given repeated dredging practices during the roman and byzantine periods 4 fine grained silts and sands in the northern harbour are coeval with advanced roman engineering works significantly deforming the coastal landscape bio and lithostratigraphical data attest a leaky lagoon type environment indicative of a well protected port 5 the technological apogee of sidon s northern harbour is recorded during the late roman and byzantine periods translated stratigraphically by a plastic clays unit and brackish lagoon fauna 6 a final semi abandonment phase comprising coarse sand facies concurs silting up and a 100 150 m progradation of the port coastline after the seventh century ad we advance three hypotheses to explain these stratigraphic data namely cultural tectonic and tsunamogenic finally our results are compared and contrasted with research undertaken in sidon s sister harbour tyre

isotopic compositions and biomarkers in crude oils from the tarim basin oil maturity and oil mixing abstract hydrogen and carbon isotopic compositions of n alkanes as well as biomarkers in various types of oil from the tarim basin were analyzed data were used to discuss the occurrence and formation of marine oils from this old composite basin of which we have limited understanding first hydrogen and carbon compositions of n alkanes clearly classify the collected oils into two distinct groups supporting the reported oil classifications based on biomarkers group i the majority of oil samples is characterized by relative enrichment in d and n alkane d values vary from 110 to 75 group ii includes two heavy oils and d values of n alkanes range from 145 to 142 second variations in the 13c value of n alkanes 2 3 show good correlations with the maturity indices indicating that kinetic isotopic fractionation is one control on the 13c value of n alkanes in the maturation process d values of n alkanes in most oils are also evidently influenced by the oil maturity finally by combining the isotopic compositions with biomarkers of oils two distinct oil mixing processes were recognized in the oils from the tabei and tazhong uplifts in this old composite basin the former process is the mixing of oils from the same source at different maturity stages while the latter involves the mixing of oils from distinct sources at different maturity stages biodegraded oils may contribute to the total oils but their proportions are minor

different response of δd values of n alkanes isoprenoids and kerogen during thermal maturation abstract this study investigates the extent of post depositional alteration of d values of n alkyl lipids isoprenoids and kerogen isolated from a continuous 450 m core that covers the transition from thermally immature to early mature sediments in the lacustrine kissenda formation lower cretaceous gabon basin large variations in d values up to 40 for n c 17 and up to 30 for n c 29 alkanes as well as up to 10 for kerogen in closely spaced samples are evident throughout the core and remain preserved even at the bottom of the section d values of individual n alkanes show a slight overall d enrichment with depth and a general trend of increasing d values with increasing n alkane chain length characterizes all samples particularly in those below 600 m depth hydrogen isotopic compositions of kerogen samples overlap with those of n alkanes throughout the section d values of pristane and phytane are more negative than those of n c 17 alkane by as much as 120 at shallow depths but increase dramatically and approach d values of n c 17 alkane in the samples closest to the oil window integration of analytical and computational results indicates that 1 n alkanes and isoprenoids have the potential to preserve the original biological signal before the onset of oil generation 2 isomeric and structural rearrangements taking place at the beginning stages of oil generation do not influence significantly the d values of n alkanes and kerogen however these processes have a major effect on the isotopic composition of isoprenoids causing isotopic d enrichment up to 90

influence of migration distance maturity and facies on the stable isotopic composition of alkanes and on carbazole distributions in oils and source rocks of the alpine foreland basin of austria abstract the austrian part of the alpine foreland basin has been studied previously by organic geochemical methods to establish oil oil and oil source rock correlations the lateral distance of oil fields to the position of mature source rocks lower oligocene schoneck and eggerding formations beneath the alpine nappes in the south suggests long distance migration up to 50 km minor compositional trends in w e direction were obtained reflecting differences in depositional environment facies and maturity of potential source rocks therefore the oil and source rock samples are thought to provide valuable insights into carbazole distributions in relation to migration distance maturity and facies compound specific carbon isotope analyses on n alkanes and isoprenoids reflect the w e trend already seen within the total hydrocarbon fractions the observed trend toward lighter 13 c values of alkanes from oil fields in a w e direction are consistent with lower 13 c values of organic matter in unit c and similar differences obtained from sediments of the schoneck formation at wells oberhofen 1 w and molln 1 e the 13 c patterns of n alkanes and isoprenoids are in agreement with data obtained from the potential marine source rocks schoneck formation of the oils the hydrogen isotopic composition of short chain n alkanes c 15 19 of most oil samples are lower than the data obtained from the extracts of the marine permian kupferschiefer of the polish zechstein basin at similar maturation stages only the oils from the western oil fields yield d values of n alkanes comparable to those obtained from marine source rocks the data imply brackish water conditions during deposition of unit c of the schoneck formation differences in the position of d of isoprenoids in relation to the respective maturation trend line are most probably related to calibration errors alkylated carbazoles and benzocarbazoles are only present in sufficient amounts for quantification in oils sampled from the eastern fields rock extracts of the schoneck formation from drill cores molln 1 5200 m depth 0 92 rr and from the marginally mature ca 0 6 rr samples from well oberhofen 1 4300 m depth obtained sufficient amounts of carbazoles the significantly different concentrations of benzocarbazoles in the extracts around 10 g g at oberhofen 1 50 g g at molln 1 are related to maturity differences whereas the predominance of 1 methylcarbazole in the oberhofen samples is inferred to reflect differences in source rock facies in the oils from the eastern deposits neither the concentration ratios of methylcarbazoles nor the benzocarbazole ratio show indications for the influence of facies differences maturity of oil expulsion is estimated on the basis of mpi 1 rc 0 76 0 88 confirmed by sterane isomerization parameters the results argue for a minor influence of maturity differences on the benzocarbazole ratios of the oil samples the obtained ratios and the reservoir source fractionation parameters calculated from the data of molln 1 source rocks and the respective oils show a systematic decrease with the estimated migration distance the results argue for the applicability of benzocarbazoles for the assessment of relative differences in migration distances in oil plays characterized by minor differences in source rock facies and maturity during oil expulsion

change in hydrogen isotope composition of n alkanes pristane phytane and aromatic hydrocarbons in miocene siliceous mudstones with increasing maturity abstract the variation in the hydrogen isotope composition d h ratio values of n alkanes pristane phytane and aromatic hydrocarbons with increasing maturity was investigated using a set of immature to mature miocene siliceous mudstones the d h values of aromatic hydrocarbons change at the earliest stage vitrinite reflectance r o 0 4 0 5 by way of higher values in immature rocks a dramatic increase in values is observed for pristane and phytane during the mature stage r o 0 6 0 7 attributable to hydrogen exchange with sediment porewater the decrease in the values of short chain n alkanes and the disappearance of carbon number predominance in n alkane d h values with increasing maturity is a result of the thermal cracking of aliphatic structures in bitumen and kerogen the long chain n alkanes derived from higher plant wax can maintain their initial values even in the zone of extensive oil generation r o

reservoir fluids and their migration into the south eugene island block 330 reservoirs offshore louisiana this study in the well documented pliocene pleistocene south eugene island block 330 sei330 field offshore louisiana unravels a complex petroleum system by evaluating both the inorganic and organic geochemical characteristics of reservoir fluids the brines at sei330 dissolved halite prior to entering the reservoirs and equilibrated with reservoir sediments exchanging sodium for calcium magnesium and other cations the systematically varying extent of brine sodium depletion in two reservoirs defines south to north flow in those sands these sands were filled from a fault that bounds the reservoirs on the south oil compositional parameters also show north south variation across these reservoirs the sei330 oils and gases each had different sources in contrast to published jurassic sources for oil carbon isotope data indicate that sei330 hydrocarbon gases probably sourced from early tertiary or cretaceous sediments after oil had migrated through them distribution of biodegraded vs unbiodegraded oils indicates the reservoirs filled much more recently than formation of the salt weld beneath the field oil compositions indicate that some sei330 oils were partially stripped of low molecular weight compounds by their dissolution in a mobile vapor phase gas washed by large volumes of gas several hundred meters below the deepest reservoir modeling of this gas oil interaction aids in identifying deep potential targets in which gas washing occurred hydrocarbon distribution combined with oil chemistry and reservoir pressures indicate reservoirs filled from fault systems on both the north and south sides of the field the fault feeders are wide 100 m structurally complex zones that can direct different types of fluids into different reservoirs

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

stable carbon isotope compositions of crude oils application to source depositional environments and petroleum alteration the carbon isotopic composition of the c15 saturate and aromatic hydrocarbon fractions and the gas chromatographs of the c15 saturate fraction of 339 oils were geochemically and statistically evaluated results of this study show that the average isotopic compositions of the c15 aromatic hydrocarbon fractions of oils sourced from terrigenous or marine organic matter are identical the average isotopic composition of the c15 saturate fraction of oils derived from terrigenous organic sources is slightly more negative 0 9 pmil than the average for marine oils but this difference is insufficient to be used as a reliable source indicator reports in the literature stating that marine oils are isotopically more positive than te rigenous oils and that the difference can be utilized to distinguish between the two are therefore not supported by this study the isotopic differences between oils sourced from terrigenous and marine organic matter do not manifest themselves in the range of absolute values of one oil fraction but rather in the isotopic relationship between the saturate and aromatic hydrocarbon fractions the isotopic relationship is the following oils of terrigenous organic source dgr13caro 1 12 dgr13csat 5 45 oils of marine organic source dgr13caro 1 10 dgr13csat 3 75 the difference between the two equations was evaluated statistically and a statistical parameter cv the canonical variable cv 2 53 dgr13csat 2 22 dgr13caro 11 65 was used to distinguish between marine and terrigenous oils cv values larger than 0 47 indicate predominantly a terrigenous organic source for the oil whereas cv values smaller than 0 47 indicate mostly a marine organic source thermal maturity differences in oils and isotopic variations in the source beds can cause as much as 2 pmil variations in the isotopic composition of one family of oils finally stable carbon isotopes can in some situations help correlate biodegraded oils to their nondegraded counterparts

two types of chemical remanent magnetization during the oxidation of magnetite abstract the chemical remanent magnetization crm m crm resulting from oxidation of equidimensional magnetite to a mixture of 90 hematite and 10 cation deficient magnetite is jointly controlled by the initial anhysteretic remanent magnetization m arm of the parent magnetite and the field h crm applied during oxidation m crm lies in the plane defined by h crm and m arm which were perpendicular in our experiments in an intermediate orientation determined by the relative strengths of h crm 0 05 0 1 and 0 2 mt and m arm 0 002 0 12 saturation remanence the crms are univectorial remanences that remain fixed in these stable intermediate directions throughout the course of stepwise alternating field and thermal demagnetization similar experiments in which acicular single domain cation deficient magnetite was oxidized to maghemite gave quite different results m crm was always parallel to m arm its direction was unaffected by field strengths as high as h crm 1 5 mt the essential factors controlling crm direction seem to be the number and crystallographic structure of oxidation products for single phase oxidation without change in crystal lattice crm remains parallel to the initial remanence of the parent mineral for multiphase oxidation to a mixture of rhombohedral and spinel phases both initial remanence and the field acting during oxidation influence the crm direction which therefore has an intermediate orientation that parallels neither m arm nor h crm

hydrogen isotopic compositions of individual alkanes as a new approach to petroleum correlation case studies from the western canada sedimentary basin isotopic compositions of carbon bound hydrogen in individual n alkanes and acyclic isoprenoid alkanes from a number of crude oil samples were measured using gas chromatography thermal conversion isotope ratio mass spectrometry the precision of this technique is better than 3 for most alkanes compared to the large range of d variation among the samples up to 160 the oils were selected from major genetic oil families in the western canada sedimentary basin with source rocks ranging in age from ordovician and possibly cambrian to cretaceous the hydrogen isotopic composition of alkanes in crude oils is controlled by three factors isotopic compositions of biosynthetic precursors source water d values and postdepositional processes the inherited difference in the lipid s biosynthetic origins and or pathways is reflected by a small hydrogen isotopic variability within n alkanes but much larger differences in the d values between n alkanes and pristane phytane the shift toward lighter hydrogen isotopic compositions from paleozoic to upper cretaceous oils in the wcsb reflects a special depositional setting and or a minor contribution of terrestrial organic matter the strong influence of source water d values is demonstrated by the distinctively lower d values of lacustrine oils than marine oils and also by the high values for oils with source rocks deposited in evaporative environments thermal maturation may alter the d values of the alkanes in the oil to some extent but secondary oil migration does not appear to have had any significant impact the fact that oils derived from source rocks that could be of cambrian age still retain a strong signature of the hydrogen isotopic compositions of source organic matter and source water indicates that d values are very useful for oil source correlation and for paleoenvironmental reconstructions

carbon and hydrogen isotope variation of plant biomarkers in a plant soil system stable carbon 13c and hydrogen d isotopic compositions of n alkanes anteiso alkanes n alkanoic acids n alkanols phytol and sterols in raw leaves of acer argutum and acer carpinifolium their fallen leaves mold and soils from a natural acer forest were measured in order to 1 understand isotopic variation of the plant biomarkers in a plant soil system and 2 evaluate which biomarker is the most effective recorder of soil vegetation long chain c24 n alkanes n alkanoic acids and n alkanols are gradually enriched in 13c up to 12 9 average of 4 3 and depleted in d up to 94 average of 55 from raw leaves to soils however anteiso alkanes phytol and sterols show little variation in both 13c 1 and d 2 from raw leaves to soils these isotope signatures in a plant soil system indicate that isoprenoid plant biomarkers such as sterols in soils faithfully preserve the isotopic compositions of dominant higher plants growing on the soils without a diagenetic effect upon the isotopic compositions in contrast long chain n alkyl molecules in soils undergo specific isotopic modification during biodegradation associated with early diagenesis and or a significant contribution from heterotrophic reworking

improved understanding of the petroleum systems of the niger delta basin nigeria biomarker and n alkane compound specific stable carbon isotope analyses csia were carried out on 58 crude oil samples from shallow water and deepwater fields of the niger delta in order to predict the depositional environment and organic matter characteristics of their potential source rocks using a source organofacies prediction approach from oil geochemistry the presence in the western deepwater oils relatively abundant c27 steranes c30 24 n propyl cholestane low oleanane index relatively low pr ph ratios gammacerane and positive to nearly flat c12 c30 n alkane compound specific stable carbon isotope profiles suggests that the source facies that expelled these oils contain significant marine derived organic matter deposited under sub oxic and stratified water column conditions this contrasts with the terrigenous organic matter dominated source rocks accepted for shallow water niger delta oils oils in the shallow water accumulations can be separated into terrigenous and mixed marine terrigenous families the terrigenous family indicates expulsion from source rock s containing overwhelmingly higher plant source organic matter average oleanane index 0 48 high c29 steranes as well as having negative sloping n alkane isotope profiles oxic source depositional conditions pr ph 2 5 and non stratified conditions absence to low gammacerane content are inferred for the terrigenous family the mixed marine terrigenous family has biomarker properties that are a combination of the deepwater and terrigenous shallow water oils bitumen extracts of the sub delta late cretaceous araromi formation shale in the dahomey basin are comparable both molecularly and isotopically to the studied western deepwater oil set but with an over all poor geochemical correlation this poor geochemical match between araromi shale and the western deepwater oils does not downgrade the potential of sub delta cretaceous source rock contribution to the regional oil charge in the deepwater niger delta

oil oil and oil source rock correlations in the alpine foreland basin of austria insights from biomarker and stable carbon isotope studies abstract the alpine foreland basin is a minor oil and moderate gas province in central europe in the austrian part of the alpine foreland basin oil and minor thermal gas are thought to be predominantly sourced from lower oligocene horizons schoneck and eggerding formations the source rocks are immature where the oil fields are located and enter the oil window at ca 4 km depth beneath the alpine nappes indicating long distance lateral migration most important reservoirs are upper cretaceous and eocene basal sandstones stable carbon isotope and biomarker ratios of oils from different reservoirs indicate compositional trends in w e direction which reflect differences in source depositional environment facies and maturity of potential source rocks thermal maturity parameters from oils of different fields are only in the western part consistent with northward displacement of immature oils by subsequently generated oils in the eastern part of the basin different migration pathways must be assumed the trend in s s r isomerisation of c29 steranes versus the 20r 20r c29 steranes ratio from oil samples can be explained by differences in thermal maturation without involving long distance migration the results argue for hydrocarbon migration through highly permeable carrier beds or open faults rather than relatively short migration distances from the source the lateral distance of oil fields to the position of mature source rocks beneath the alpine nappes in the south suggests minimum migration distances between less than 20 km and more than 50 km biomarker compositions of the oils suggest oligocene shaly to marly successions i e schoeneck dynow and eggerding formations as potential source rocks taking into account their immature character best matches are obtained between the oils and units a b marly shale and c black shale of the normal schoneck formation as well as with the so called oberhofen facies results from open system pyrolysis gas chromatography of potential source rocks indicate slightly higher sulphur content of the resulting pyrolysate from unit b the enhanced dibenzothiophene phenanthrene ratios of oils from the western part of the basin would be consistent with a higher contribution of unit b to hydrocarbon expulsion in this area differences in the relative contribution of sedimentary units to oil generation are inherited from thickness variations of respective units in the overthrusted sediments the observed trend towards lighter 13c values of hydrocarbon fractions from oil fields in a w e direction are consistent with lower 13c values of organic matter in unit c

a comparative study of the stable carbon isotopic composition of crude oil alkanes and associated crude oil asphaltene pyrolysate alkanes abstract normal alkanes and isoprenoid alkanes in crude oils and micro sealed vessel pyrolysates of related asphaltenes sourced from different source rock types have been analysed by gas chromatography isotope ratio mass spectrometry gc irms seven sample sets each consisting of the oil and the related asphaltene from marine non clastic sources marine clastic source a lacustrine clastic source and two from sources from land plant dominated deltaic facies source rocks angiosperm and gymnosperm dominated plant inputs respectively were studied the utility and precision of the gc irms technique are assessed by analysing a a standard n alkane mixture of known isotopic values and a blend of this standard mixture with b a biodegraded oil and c a branched cyclic saturated hydrocarbon fraction the precision of the technique is better than ca 0 25 in four sample sets the individual n alkanes of the asphaltene pyrolysates are enriched in 13c up to 4 compared to the n alkanes in the corresponding oils and follow broadly the same trend with increasing carbon number in the remaining three sample sets marine clastic lacustrine and deltaic gymnosperm derived samples the opposite trend is observed i e here the n alkanes from the asphaltene pyrolysate are isotopically lighter thus perhaps indicating different sources for the n alkanes in the oil and n alkyl moieties in the asphaltenes

magnetization of the oceanic crust thermoremanent magnetization of chemical remanent magnetization we propose a model in which chemical remanent magnetization crm acquired within the first 20 m y of crustal evolution may account for 80 of the bulk natural remanent magnetization of older basalts the crm of the crust is acquired as the original thermoremanent magnetization trm is lost through low temperature alteration the crm intensity and direction are controlled by the posternplacement polarity history this model explains several independent observations concerning the magnetization of the oceanic crust the model accounts for amplitude and skewness discrepancies observed in both the intermediate wavelength satellite field and the short wavelength sea surface magnetic anomaly pattern it also explains the decay of magnetization away from the spreading axis and the enhanced magnetization of the cretaceous quiet zones while predicting other systematic variations with age in the bulk magnetization of the oceanic crust the model also explains discrepancies in the anomaly skewness parameter observed for anomalies of cretaceous age further our study indicates varying rates of trm decay in very young crust which depicts the advance of low temperature alteration through the magnetized layer

compound specific carbon isotope analysis of natural and artificially generated hydrocarbons in source rocks and petroleum fluids from offshore mid norway stable carbon isotope signatures of individual hydrocarbon components provide important information on the source rock facies of oils as well as their asphaltene fractions despite maturity variations and secondary processes such as phase fractionation and biodegradation our study is based upon petroleum fluids and source rock samples from offshore mid norway where the main source rock is the marine shales of the upper jurassic spekk formation an alternative source is provided by coals and coaly shales of the lower jurassic are formation in terms of maturity the source rock samples are distributed throughout the main phase of oil generation in this study compound specific carbon isotope analysis has been performed on thermal extracts and kerogen pyrolysates of the source rocks as well as on the oils and the pyrolysis products of their asphaltenes we demonstrate that trends of absolute isotope data and specific isotopic fingerprints after normalizing the data are useful for petroleum source rock correlations the carbon isotope ratios of the n alkanes separate the are from the spekk formation samples in both thermal extracts and kerogen pyrolysates becoming less negative with increasing terrestrial input the spekk samples also tend to become isotopically heavier with increasing maturity while the are samples do not show any systematic difference with increasing maturity the carbon isotope ratios of the n alkanes also discriminate between the oils as well as the asphaltenes from the fluids the individual components generated by pyrolysis of kerogens are isotopically heavier than those from the thermal extracts this is expected from models of kinetic isotope effects which predict that the isotopically lightest products are generally released at an earlier stage in the maturation process a similar isotopic difference is also observed between the pyrolysis products of asphaltenes and the original oils derived from the same source rock type however in a sample where the oil and its asphaltene fraction originate from two different source rocks the opposite relationship between the carbon isotope composition of the oil and its asphaltene fraction is observed bulk isotope data of kerogen concentrates pyrolysates and the residue after pyrolysis of the source rock samples as well as bulk isotope data of whole oils are also presented we show that besides separating are from spekk the bulk carbon isotope values of the spekk samples are considerably heavier than the n alkanes from the thermal extracts whereas those of the are samples are almost equal

aspects of petroleum basin evolution due to gas advection and evaporative fractionation abstract criteria are proposed for the recognition of depletion by evaporative fractionation in reservoir fluid analyses pvt data the characteristics of original as generated molar concentration profiles of marine oils are postulated oils derived from clastic or carbonate sediments bearing respectively type ii or iis kerogens in unaltered marine oils two decreasing exponential concentration series occur separated by a discontinuity between p5 the 5 carbon pseudo component and p6 such that p6 exceeds p5 rendering the profile abruptly bimodal a suite of 195 detailed pvt analyses c1 to p30 of reservoir fluid oils shows that concentrations in the p6 fraction are frequently perturbed the maximum migrating to p7 p8 or a higher carbon number alteration attributable to additive gas advection followed by evaporative fractionation in the subject oils four variables are adduced which track these changes c1 c2 p4 p8 e3 a light gas liquid heavy end ratio and e7 a gasoline range heavy end ratio increase in c1 c2 is accompanied by decreasing values of p4 p8 for which there is no a priori rationale other than the precepts of evaporative fractionation involving the advection of highly mature dry gas dividing a suite of 535 pvt analyses detailed analyses plus 340 analyzed to p7 of world wide provenance into seven subsets on the basis of c1 c2 ratios a well defined separate regression of gas oil ratio on saturation pressure is revealed in each subset such correlations depend primarily upon the processes involved in evaporative fractionation the curves embrace the full commonly encountered range of combinations of gas oil ratio and saturation pressure both of which correlate poorly with level of maturity expressed in a liquid fraction slope factor these observations lead to the hypothesis that progressive evaporative fractionation is a widespread if not universal evolutionary process in petroleum basins

late holocene relative sea level changes in lebanon eastern mediterranean twenty nine 14 c dates of precise biological sea level indicators from the lebanese coast show evidence for two significant regional crustal uplift episodes during the past 6000 years we elucidate 1 an upper shoreline at ca 120 to 140 cm which lasted from ca 6000 to 3000 bp and 2 a lower shoreline at 80 40 cm developed between the fifth century bc and the sixth century ad these movements are associated with 1 two major seismic crises along the yammuneh fault and the roum tripoli thrust rtt and 2 subsequent seismic events on a series of second order ene trending dextral transpressive faults vertical movements affected north lebanon whilst the coasts of south lebanon generally underwent crustal downlift this is in contrast with relative stability in northern israel suggesting an area of stationary tectonic conditions west of the dead sea rosh hanikra ras nakoura fault the main 14 c age cluster corresponding to the second uplift event may have resulted from fault movements during the early byzantine tectonic paroxysm ebtp between ca 1750 and 2000 bp relative sea level stabilised to present level around 1000 bp 2006 elsevier b v all rights reserved

oil families and their inferred source rocks in the barents sea and northern timan pechora basin russia a geochemical study of 34 oil samples was conducted to understand the types and distributions of effective source rocks and evaluate the geographic extent of the petroleum systems in the barents sea and northern timan pechora basin taxon specific age related and source related biological markers biomarkers and isotope data provided information on the depositional environment of the source rock source input and source age of the oil samples a relationship between biomarker and diamondoid concentration was used to identify mixed oils having both oil window and highly cracked components compound specific isotope analyses of diamondoids and n alkanes were used to deconvolute cosourced oils and identify deep source rocks in the basin results suggest five major source rocks in the barents sea and the northern timan pechora basin upper jurassic shale lower middle jurassic shale triassic carbonate and shale devonian marl and devonian carbonate the upper and lower middle jurassic source rocks are dominant in the barents sea triassic source rock consists of carbonate in the onshore part of northern timan pechora basin and marine shale in the barents sea the devonian domanik formation carbonate source rock extends offshore into the southern barents sea the high maturity domanik formation could also be a secondary source rock for most of the mixed oils in the northern timan pechora basin this detailed geochemical study provides a new and detailed understanding of petroleum systems in the barents sea and northern timan pechora basin

organic carbon as a palaeoenvironmental indicator in the marine realm recent developments in biogeochemistry have made accessible all information currently known to be present in sedimentary organic compounds i e the carbon skeleton structure the positions of functional groups and stable carbon isotope ratios this combined information has strengthened the applications of sedimentary organic compounds as biomarkers and palaeoenvironmental indicators this review summarizes the most important biomarkers and their applications in reconstructing marine palaeoenvironments and processes the marine environment is characterized by the combined presence of specific compounds such as organic sulphur compounds dinosteroids 24 n propylsteroids even in trace amounts high amounts of c hbi hydrocarbons and the absence of long chain n alkanes with odd over even predominance bicadinanes and specific higher plant triterpenoids e g oleanane furthermore palaeoenvironmental conditions such as photic zone anoxia hypersalinity microbial sulphate reducing activity algal blooming palaeo upwelling and palaeo surface seawater temperature are indicated by molecular and or isotopic characteristics biomarkers from terrestrial sources are included because land derived organic matter is an important contributor to coastal and shallow marine environments a short case study within a holocene terrestrial marine setting florida bay usa is also presented to illustrate the reconstruction of transgressive regressive trends using selected organic compounds

gas washing of oil along a regional transect offshore louisiana abstract gas chromatogram data for 219 oils in a 190 km n s transect offshore louisiana reveal a spatially coherent pattern of compositional change which is caused by gas washing near the louisiana shoreline as much as 91 of the original n alkanes have been removed from the oils the maximum intensity of depletion decreases southward in a nearly regular fashion to nil at the jolliet field 190 km offshore the oils show a parallel change in the maximum carbon number of the removed n alkanes implying that the pressure at which gas washing took place also decreased in the offshore direction the systematic change in maximum extent of depletion crosscuts tectonostratigraphic boundaries as well as oil source provinces models of gas washing suggest that the maximum depth of washing reflects the distribution of deeply buried continuous sands suggesting deep sands may have provided sites for efficient gas oil interaction

effects of thermal maturation on stable organic carbon isotopes as determined by hydrous pyrolysis of woodford shale acquiring crude oils that have been expelled from the same rock unit at different levels of thermal maturation is currently not feasible in the natural system this prevents direct correlation of compositional changes between the organic matter retained in a source rock and its expelled crude oil at different levels of thermal maturation alleviation of this deficiency in studying the natural system requires the use of laboratory experiments natural generation of petroleum from amorphous type ii kerogen in the woodford shale may be simulated by hydrous pyrolysis which involves heating crushed rock in contact with water at subcritical temperatures 374 c four distinct stages of petroleum generation are observed from this type of pyrolysis 1 pre oil generation 2 incipient oil generation 3 primary oil generation and 4 post oil generation the effects of thermal maturation on the 13c values of kerogen bitumen and expelled oil like pyrolysate from the woodford shale have been studied through these four stages of petroleum generation similar to the natural system the kerogens isolated from the pyrolyzed rock showed no significant change in 13c this suggests that the 13c value of kerogens may be useful in kerogen typing and oil to source rock correlations 13c values of bitumens extracted from the pyrolyzed rock showed an initial decrease during the incipient oil generation stage followed by depletion during the primary and post oil generation stages this reversal is not favorable for geochemical correlation or maturity evaluation saturated and polar components of the bitumen show the greatest 13c variations with increasing thermal maturation the difference between the 13c of these two components gives a unidirectional trend that serves as a general indicator of thermal maturation and is referred to as the bitumen isotope index bii 13c values of the expelled pyrolysates show a unidirectional increase with increasing thermal maturation the constancy and similarity of 13c values of the aromatic components in the expelled pyrolysates and bitumens with increasing thermal maturation encourages their use in oil to oil and oil to source rock correlations isotopic type curves for expelled pyrolysates indicate that they may be useful in oil to oil correlations but have a limited use in oil to source rock correlations

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

holocene raised shorelines on the hatay coasts turkey palaeoecological and tectonic implications abstract the marks of two emerged shorelines superimposed erosional notches and in situ bioconstructed rims with the vermetid dendropoma on both sides of the orontes delta near the border between turkey and syria are interpreted as representing the occurrence of two rapid uplifts during the late holocene rather than representing eustatic fluctuations of climatic origin as claimed by previous authors in other areas of the eastern mediterranean the upper shoreline which has an elevation of about 2 0 m south of the delta and which increases from 2 5 m to 3 0 m between 2 and 8 km north of the delta has been radiocarbon dated four dates to between 5170 190 and 2595 100 yrs b p the lower shoreline indicating a former relative sea level situated consistently at about 0 7 to 0 8 m has yielded seven dates between 2910 95 and 1345 70 yrs b p the latter age being that of fossil oyster shells collected in growth position on a quay of the ancient harbour of seleucia pieria if the possible contamination of some oyster shells is taken into account the two uplift movements may be dated at around 2500 100 yrs b p for the upper shoreline and to historical times for the lower shoreline probably in july 551 a d when devastating earthquake damage was reported from all the levant regions the age of the second uplift movement falls within the possible time span of a major tectonic event the early byzantine tectonic paroxysm ebtp which about 1500 yrs b p caused sudden relative sea level changes in various areas of the eastern mediterranean antikythira western crete and alanya area the lebanon northern cyprus etc in the hatay region the effect of the ebtp has been a reactivation of local fault lines probably in connection with movements on the east anatolian fault system this has contributed a new jerk to the long term trend of uplift in this coastal area

source characteristics of marine oils as indicated by carbon isotopic ratios of volatile hydrocarbons carbon isotopic ratios of volatile hydrocarbon fractions of marine oils are diagnostic of organic facies and depositional environments of source rocks for carbonate oils low molecular weight volatile hydrocarbons c9 are isotopically lighter than high molecular weight volatile hydrocarbons c9 c17 in contrast for deltaic oils low molecular weight volatile hydrocarbons are isotopically heavier than high molecular weight volatile hydrocarbons marine shale oils show patterns intermediate between carbonate and deltaic oils this relative variation of carbon isotopic ratios among volatile hydrocarbons of oils is explained by earlier expulsion of marine oils derived from isotopically homogeneous algal bacterial kerogens in rich so rce rocks and secondary cracking of petroleum prior to expulsion for marine oils derived from isotopically heterogeneous terrestrial kerogens in lean source rocks in basins with multiple source rocks carbon isotopic ratios of volatile hydrocarbons are useful for determining oil oil correlation and for inferring oil source rock relationship

holocene valley fills of southern turkey and northwestern syria recent geoarchaeological contributions abstract holocene alluvial fills from catchments ranging from 100 000 km 2 the upper euphrates are described for part of s anatolia and nw syria the sequences indicate that mid holocene landscapes were moderately stable and in several areas were drained by reliable perennial channel flows although the boundary between mid and late holocene deposits ca 2000 bc is represented by sedimentary discontinuities in several alluvial sequences these transitions were not necessarily contemporaneous in places ploughwash deposits infilled valleys where sediment delivery had exceeded channel flow during the last 4000 5000 y in the balikh valley human withdrawal of water for irrigation has depleted flow thereby weakening that river as a palaeohydrological indicator the limited lacustrine sequences do not necessarily provide a reliable palaeoclimatic record because they may relate to increased flood frequency from the inflowing rivers which may in turn result from a range of anthropogenic and natural factors late holocene channel fills indicate less perennial flow higher flow variations increased erosion or accelerated aggradation such environments appear to have characterized the last 4000 5000 yr during which time the impact of human population on the landscape increased and climatic desiccation albeit at fluctuating levels had probably become more pronounced

facies evolution and stratigraphic correlation in the early oligocene tard clay of hungary as revealed by maceral biomarker and stable isotope composition abstract hydrocarbon source rocks i e tard clay formation containing type ii organic matter were deposited in the hungarian paleogene basin during lower oligocene a major contribution of aquatic organisms green algae dinoflagellates chrysophyte algae and minor inputs from macrophytes and land plants to organic matter accumulation is indicated by n alkane distribution patterns composition of steroids and 13c of hydrocarbon biomarkers microbial communities included heterotrophic bacteria cyanobacteria chemoautotrophic bacteria as well as green sulphur bacteria the presence of methanotrophic bacteria is indicated by 13c depleted hop 17 21 ene higher inputs of terrestrial organic matter occurred during deposition of the lower and uppermost units of the tard clay formation the terpenoid hydrocarbon composition argues for angiosperm dominated vegetation in the area of the hungarian paleogene basin diterpenoid hydrocarbons derived from the resins of conifers are about 2 3 enriched in 13c compared to the angiosperm biomarkers environmental conditions changed from marine to brackish accompanied by oxygen depletion in the lower parts of the water column organic carbon accumulation during this period was a consequence of stagnant bottom water conditions in the hungarian paleogene basin due to salinity stratification this is indicated by low pristane phytane ratios varying from 0 27 to 1 44 enhanced ratios of dimethylated versus trimethylated mttcs 0 14 0 59 and the presence of aryl isoprenoids from 0 4 to 14 1 g g toc a major marine incursion is evidenced by stable isotope ratios of organic matter and carbonates in the uppermost member of the tard clay a transition from brackish towards normal marine conditions is proposed up to 3 anoxic cycles are recognized in the drill core sections separated by minima in pristane phytane ratios and maxima in the depth trends of di tri methylated mttcs and aryl isoprenoid concentrations in combination with the position of maxima of 13c of carbonate and organic matter and an abrupt decrease in perylene concentrations the cycles can be used for intra formational correlation of the tard clay