organic matter source and thermal maturity within the late cretaceous niobrara formation u s western interior abstract the late cretaceous sedimentary record of the north american western interior seaway is characterized by cyclic deposition of organic carbon rich sediments one notable interval during the late coniacian santonian is recorded by the niobrara formation the organic carbon rich interval within the niobrara formation has been identified as oceanic anoxic event oae 3 understanding the reason for this distribution of organic carbon within the niobrara formation requires a refined understanding of the source and maturity of the organic matter in this study we present lipid biomarker records from the usgs portland 1 core canon city co to constrain the thermal maturity of the organic matter and the differing contributions of organic matter sources sterane and hopane thermal maturity indices indicate that the samples are somewhat immature with respect to oil formation and that there is strong agreement between different proxies for thermal maturity based on the distribution of n alkanes steranes and hopanes there is a significant increase in the contribution of algal organic matter during and after oae 3 coeval with increased organic carbon accumulation although a consistent terrestrial contribution is observed it is only a minor source of organic matter at the portland core location and does not drive increased organic matter accumulation during oae 3 of particular note is the consistent influence of even over odd predominantly mid chain length c21 to c25 organic matter this observation within the brackish to marine not methanogenic wis represents an expansion of the depositional settings in which even over odd predominance has been observed in mid chain length n alkanes pristane pr and phytane ph abundances are inconsistent with a redox control on pr ph ratios and suggest an increase in the delivery and or preservation of phototrophic organic matter as the source for pristane and phytane in the portland core

a three dimensional surface velocity field for the mississippi delta implications for coastal restoration and flood potential accurate estimates of the current rate of subsidence in the mississippi delta southern united states provide a context for planning of wetland restoration and predictions of storm surge flooding we present a comprehensive three dimensional surface velocity field for the mississippi delta based on a network of 36 high precision continuous gps stations we show that while the majority of the delta is relatively stable the southern portion continues to experience high rates of subsidence 5 6 mm yr 1 our data are consistent with long term tide gauge records at grand isle louisiana and several stations in florida the current rate of relative sea level rise combined effect of land subsidence and sea level rise along parts of the coastal delta is 8 9 mm yr 1 most tide gauge stations have recorded sea level rise acceleration after a d 1970 these data have implications for land reclamation and wetland restoration in the region parts of the delta may not be viable in the long term

holocene climate change in northeastern china reconstructed from lipid biomarkers in a peat sequence from the sanjiang plain abstract lipid biomarkers extracted from a sediment peat sequence from the sanjiang plain were analyzed to assess the change in regional vegetation and climate during the last 8 ky the combination of n alkane and n alkanoic acid distributions and published pollen and plant macrofossil records for the lake sediments underlying the peat reveal that the region experienced a warmer and wetter period before ca 6 ka that corresponds to the monsoon maximum and holocene climate optimum in northeast china the climate then entered a cold and wet period from 6 to 4 ka a shift to warmer and drier conditions starting 4 ka is recorded as a transformation from a shallow lake to a peat deposit from 1 5 to 0 4 ka the region entered a cold and wet period that was followed by warm and dry conditions for the most recent 0 4 ky our lipid based paleoclimate reconstruction was compared with holocene reconstructions based on lipid records from the nearby hani peat sequence peat cellulose 13c results from the jinchuan peat sequence and pollen records from other lakes in northeast china most of the regional paleoclimate changes reconstructed from the lipid proxies in the sanjiang plain peat sequence have a strong link with sea surface temperature changes in the sea of japan that were influenced by summer solar insolation at 65 n and the east asia summer monsoon in contrast the change to the warmer and drier conditions of the last four centuries seems to be mainly a consequence of human activity

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

an integrated analytical approach for determining the origin of solid bitumens in the mcarthur basin northern australia abstract an integrated analytical approach using petrological geochemical and isotopic techniques has been used to determine the origin of solid bitumens in the middle proterozoic roper group mcarthur basin northern australia sandstone and dolerite samples which in hand specimen contain dark material believed to be solid bitumens were examined from six wells under ultraviolet illumination non fluorescent solid bitumens can be distinguished from two generations of crude oil one of lower maturity orange fluorescence the other of higher maturity white fluorescence other petrographic observations indicate that the precursor hydrocarbons to the solid bitumens and the subsequent charges of crude oil postdate all diagenetic clay and quartz cementation geochemical analyses indicate that many of the sandstones contain both an aliphatic rich oil and solid bitumen mixed in varying proportions thus corroborating the petrological results on the basis of n alkane distributions the oil appears to have two 3ubtly different source inputs one of which is typified by a greater proportion of high molecular weight n alkanes which have a slight even carbon number predominance and an isotopically lighter aliphatic hydrocarbon fraction one sandstone sample contains solid bitumen in a fracture which is characterized by a high abundance of asphaltenes polar compounds and sulphur and may have formed by deasphalting of a precursor oil the solid bitumens recovered from fractures in dolerite sills were formed by thermal processes which in one sample resulted in an unusual series of ketone isomers however most solid bitumens particularly where present in the coarser sandstones are related to the generation of secondary porosity the large proportion of unresolved complex mixture the lack of n alkanes and the isotopically heavier aliphatic hydrocarbon fractions of samples containing predominantly solid bitumens indicate that bitumen formation occurred mainly by biodegradation of a precursor oil

predominance of even carbon numbered n alkanes from lacustrine sediments in linxia basin ne tibetan plateau implications for climate change this study reports the first observation of predominant even c numbered n alkanes from sediments in the continuous lacustrine sedimentary section maogou from the late miocene to the early pliocene 13 4 4 ma in the linxia basin ne tibetan plateau the n alkanes showed a bimodal distribution that is characterised by a centre at n c16 n c20 with maximum values at n c18 and n c27 n c31 as well as at n c29 the first mode shows a strong even c number predominance oep16 20 0 34 0 66 in contrast the second mode has a strong odd c number predominance oep27 31 1 20 2 45 certain types of special autochthonous bacteria are a possible source for this distribution of even c numbered n alkanes in lacustrine sediments these bacteria may have a high production rate in weak oxic anoxic and arid depositional environments in which a variety of geochemical parameters have recorded palaeoclimate change

aliphatic hydrocarbons and triterpenes of the congo deep sea fan abstract hydrocarbons were analyzed in sediments from the congo river deep sea fan from the congo river and in sinking particles collected by sediment traps 40 m above the sediment studied sites encompassed three lobes of decreasing age of formation along the canyon sites a f and c and a another lobe system disconnected from the active channel since 4 ka site e terrestrial long chain odd n alkanes were dominant in all sediments of the lobe system unsaturated terpenoids sourced by higher plants such as gammacerene lupene ursene and oleanene were also detected at site c characterized by high accumulation rates 10 20 cm yr 1 the organic matter spends less time in the oxic layer than at other sites and high phytadiene concentrations 10 17 g g oc 1 evidenced recent terrestrial and phytoplanktonic remains reworked in anaerobic conditions in these sediments organic carbon normalized concentrations of terrestrial alkanes and terpenoids were several fold higher than in the lobe sediments with lower accumulation rates sites a and f arguing for a more rapid degradation of terrestrial hydrocarbons than bulk organic carbon in the first steps of pre diagenesis ample variations in the contributions of biomarkers from higher plants ferns bacteria and angiosperms indicate an heterogeneous contribution of the soil and vegetation detritus delivered to the congo lobe sediments lower concentrations in terrestrial hydrocarbons at site e 45 km away from the active canyon indicated that river particles are still admixed to the dominant marine organic matter diploptene and hop 7 21 ene have a dual origin from terrestrial and marine microorganisms scatter in their relationship to gammacerene argues for a contribution of marine microorganisms in addition to soils sourced microorganisms the close distribution patterns of diploptene hop 21 ene hop 7 21 ene and neohop 13 18 ene is in line with the hypothesis of sequential clay catalyzed isomerisation of bacterial hopenes terrestrial biomarker accumulation fluxes at site c are one order of magnitude higher than vertical pelagic flux demonstrating the magnitude of the inputs delivered through turbiditic transport in the submarine canyon crude oil contamination was evidenced at the disconnected site e ucm c 21 to c 26 tricyclic diterpanes cpi and in smaller amounts in some sediments from sites a and c it may be related to marine crude oil extraction and transport a short chain mode of alkanes with an even predominance is evidenced in sediments of the lobe complex and likely sources crude oil microorganisms and ferns are discussed

molecular 13c and 14c evidence for the allochthonous and ancient origin of c16c18 n alkanes in modern soils the heterogeneous isotopic composition of c3 and c4 plants can be used to to follow the fate of plant carbon into soil organic molecules thus after 23 years of cropping of maize c4 on a soil which was previously under c3 vegetation c25 c33 soil n alkanes are 13c enriched up to 9 relatively to the initial c3 soil reflecting the input of 13c enriched n alkanes from maize waxes in sharp contrast c16 c18 soil n alkanes do not show any significant 13c 12c variation over the same time interval this absence of isotopic variation along with consideration of their relative concentration absolute concentration and biodegradability demonstrate that these substances must represent a regular input from an external source evidence of a large contribution of an ancient source amounting to more than 65 of the alkane fraction is given by a 14c age of 8510 yrs bp moreover short chain n alkanes from soils diesel fuel diesel automobile exhaust and petroleum products exhibit similar distributions and 13c values these findings suggests that c16 c18 soil n alkanes represent a non point source pollution of ancient hydrocarbons either carried by aerosols or entering the soil via continuous hydrocarbon seepage from the deep sedimentary rocks of the paris basin

carbon isotopic shift and its cause at the wuchiapingian changhsingian boundary in the upper permian at the zhaojiaba section south china evidences from multiple geochemical proxies abstract the late permian environmental change connecting the guadalupian lopingian g l middle upper permian boundary mass extinction and the permain triassic p tr boundary mass extinction has attracted more and more attentions a significant negative shift for carbon isotope had been found at the wuchiapingian changhsingian w c boundary in the upper permian recently however the cause s of this negative excursion is still unknown to resolve this problem we analyzed the bulk organic carbon isotope total organic carbon toc content pyritic sulfur spy content major element concentrations and molecular organic biomarkers in the wujiaping and dalong formations in the upper permian from the zhaojiaba section in western hubei province south china our results show that 1 there was a significant negative excursion in organic carbon isotopes at the w c boundary and again a negative excursion at the top of changhsingian stage 2 the significant negative excursion at the w c boundary was probably a global signal and mainly caused by the low primary productivity and 3 the negative carbon isotope excursion at the top of changhsingian was probably caused by the siberian traps eruptions a decline in oceanic primary productivity at the w c boundary probably represents a disturbance of the marine food web leading to a vulnerable ecosystem prior to the p tr boundary mass extinction

reconstruction of palaeohydrological conditions in a lagoon during the 2nd zechstein cycle through simultaneous use of δd values of individual n alkanes and δ 18 o and δ 13 c values of carbonates for the first time 18o and 13c values from carbonates and d values of individual n alkanes were used to reconstruct palaeohydrological conditions in a lagoon at the southern margin of the central european zechstein basin cezb a 12 m core covering the complete ca2 interval and adjacent anhydrites a1 and a2 was analyzed for 18o and 13c values of dolomitized carbonates and d values of individual n alkanes 18ocarb values 2 to 5 vs vpdb were strongly influenced by evaporation and temporal freshwater input into the lagoon the 13ccarb values 1 to 4 vs vpdb were controlled mainly by changes in primary production both isotopic ratios show an inverse relationship throughout most of the core contradicting diagenetic alteration since 13ccarb values are not altered significantly during dolomitization assuming a temperature range of 35 40 c in the lagoon 18ocarb values of 2 5 to 8 vs vsmow for the lagoonal water can be reconstructed the lagoon may have desiccated twice during the ca2 interval as indicated by very high 18ocarb and low 13ccarb values coinciding with increasing amount of anhydrite in the analyzed sample these events seem to reflect not just local but a regional intra ca2 cyclicity measured d values of the short chain n alkanes namely n c16 and n c18 which are widely used as indicators for photosynthetic bacterial and algal input reflect the isotopic composition of the lagoonal water assuming constant fractionation during incorporation of hydrogen into lipids of 160 an average d value of 70 vs vsmow can be reconstructed for the lagoonal water accounting for very arid conditions the long chain n alkanes n c27 n c28 n c29 and n c30 thought to be derived from the leaf waxes of terrestrial higher plants were shown to be depleted in d relative to the short chain alkanes therefore indicating a different hydrogen source terrestrial plants in arid areas mainly use water supplied by precipitation by using a smaller fractionation of 120 due to evaporation processes in the leaves reconstructed values vary between 74 and 9 vs vsmow these values are not indicating extremely arid conditions implying that the long chain n alkanes were transported trough wind and or rivers into the lagoon at the zechstein sea coast dwater values reconstructed using the n c16 alkane and 18o water values independently reconstructed on the same sample using the temperature dependant fractionation for dolomites are good agreement and suggest high amounts of evaporation affecting the coastal lagoon altogether our results indicate that hydrogen isotopic ratios of n alkanes give information on their origin and are a useful proxy for palaeoclimatic reconstruction

compound specific c and h isotope compositions of enclosed organic matter in carbonate rocks implications for source identification of sedimentary organic matter and paleoenvironmental reconstruction the bohai bay basin is one of the most important oil producing provinces in china molecular organic geochemical characteristics of lower paleozoic source rocks in this area have been investigated by analyzing chemical and isotopic compositions of solvent extracts and acid released organic matter from the lower paleozoic carbonate rocks in the jiyang sub basin of the bohai bay basin the results indicate that enclosed organic matter in carbonate rocks has not been recognizably altered by post depositional processes two end member compositions are suggested for early organic matter trapped in the lower paleozoic carbonate rocks 1 a source dominated by aquatic organisms and deposited in a relatively deep marine environment and 2 a relatively high saline evaporative marine depositional environment in contrast chemical and isotopic compositions of solvent extracts from these lower paleozoic carbonate rocks are relatively complicated not only inheriting original characteristics of their precursors but also overprinted by various post depositional alterations such as thermal maturation biodegradation and mixing therefore the integration of both organic matter characteristics can provide more useful information on the origin of organic matter present in carbonate rocks and the environments of their deposition

latitudinal change of normal paraffin composition in the northwest pacific sediments abstract we analyzed normal saturated paraffins n paraffins in 70 surface sediments in the northwest pacific to examine the spatial distribution of organic materials all sediments show bimodal n paraffin abundance patterns against carbon number with maxima at c 16 and c 31 indicating that n paraffins in marine sediments are a mixture of long chain n paraffins from land based higher plant waxes and short ones from marine organisms we observed in this study a significant change of carbon preference index cpi from 2 5 in low latitudes to 4 5 in mid high latitudes around 19 25 n the following influences are discussed as the cause of cpi offset between low and mid high latitudes 1 meteorological conditions 2 n paraffin composition of higher land plants 3 contribution of petroleum components and 4 mixing ratio of higher land plants and marine organisms however none of them can be the possible cause of the cpi offset because n paraffin content and composition vary significantly according to the species of a bacterium difference of the species of bacterial communities between low and mid high latitudes may be a possible reason for the cpi offset found in sediment from the northwest pacific

organic petrological and geochemical appraisal of the upper jurassic naokelekan formation kurdistan iraq abstract upper jurassic naokelekan formation being part of the intercepted strata of the well known miran oilfield in kurdistan region of northern iraq has been previously extensively evaluated as a potential effective source rock mainly by means of organic geochemistry in the present study a total of 60 samples were collected from four naokelekan fm outcrops those of banik galy derash barsarin and dwawa in order to conduct organic petrographical study and organic geochemical assessment including both biomarker and rock eval analyses the average recorded toc content for banik galy derash barsarin and dwawa section is considerable to very high corresponding to values of 27 5 9 0 3 5 and 5 2 wt respectively with the highest values representing the notably organic rich bottom part of the formation known as coal layer according to the petrographical analysis solid migrabitumens comprise the predominant component for all the analysed samples whereas the maceral groups of vitrinite liptinite and or inertinite showcase a minor to trace occurrence in terms of organic geochemistry each of the four sections of interest shows a different biomarker profile nevertheless a number of calculated parameters related to kerogen type and depositional conditions including the isoprenoids n alkanes ratios suggest a mixed terrestrial marine organic matter furthermore as indicated by the ro measurements along with rock eval parameters and the vitrinite reflectance equivalent based on aromatic compounds the maturity level is marginally mature in the cases of banik and galy derash whereas in the cases of dwawa and barsarin sections it is mature to post mature a synthesis of the organic petrography and geochemical appraisal applied in the present study suggests that the reported solid hydrocarbons in naokelekan fm particularly at its basal layers are non indigenous migrated and the precursor organic matter was deposited in a marine environment under oscillating conditions ranging from euxinic to well oxygenated accordingly the organic features of the notably bitumen rich coal bed fit the profile of a reservoir and or migration path

lipid distribution in the lake ennamangalam south india indicators of organic matter sources and paleoclimatic history abstract we have undertaken a comprehensive study on sediments catchment surface and core and modern vegetation samples in and around lake ennamangalam south india with focus on the reconstruction of past climate during mid to late holocene epoch using lipid biomarkers n alkanes distribution and carbon isotopic composition of organic matter 13com the retrieved ca 1 65 m long well dated sediments from the lake ennamangalam span the past ca 4800 cal bp the n alkane indices such as paq carbon preference index cpi terrestrial vs aquatic ratio tar have been used to infer the changes in source of organic matter and to reconstruct past environmental changes the end member 13c value based calculation on abundances of c3 and c4 vegetation using 13com value provided an erroneous estimation of past vegetation due to lake eutrophication or organic matter alteration by microbial degradation on the other hand long chain n alkane was not affected by bacterial activity and can be used to infer terrestrial vs aquatic productivity through the modified n alkane indices symbiotic contribution from aquatic productivity was inferred as the p aq value always exceeds 0 2 higher tar value observed after ca 3000 cal bp indicate increased precipitation in the region

unusual normal alkane distributions in offshore new zealand sediments the occurrence of unique even carbon dominated normal alkanes in sediment extracts was confirmed in sediments from the eastern continental shelf offshore of north island new zealand in hawke bay the range in carbon chain lengths was from n c16 to least n c36 extending distributions well beyond the previously reported 24 carbons stable isotope analysis of individual alkanes suggest an independent origin for the odd and even n alkanes it is suggested that sedimentary even number n alkane predominances are more widespread than previously thought but go unrecognized due to substantial overprinting by terrestrial derived odd carbon number n alkanes

hydrothermal geochemistry of sediments and pore waters in escanaba trough odp leg 169 geochemical studies of pore fluids and solid phases in two ocean drilling program odp drill sites sites 1037 and 1038 in the escanaba trough off northern california have provided further data on the hydrothermal processes associated with the spreading of the gorda ridge previous work in the area of odp site 1038 includes the discovery of a hydrothermal system and associated sulfide deposits centered around an uplifted sediment hill in this sedimented extensional environment this earlier work provided some insights into the present nature of venting however only deep drilling investigations can provide the means to fully understand the genesis and evolution of this system and associated hydrothermal deposits odp leg 169 is the third deep drilling operation to explore the magnitude genesis and evolution of hydrothermal systems on sedimented ridges previous studies centered on the guaymas basin in the gulf of california and the middle valley in the ne pacific ocean pore water studies in the reference odp site 1037 and in the hydrothermally active area of odp site 1038 have revealed the presence of a complex system of hydrothermally originated fluids whereas the data in the reference site indicate recent hydrothermal activity in the basal part of the drill site the evidence in site 1038 suggests that fluids of hydrothermal origin spread out at shallow depths around the central hill causing substantial sediment alteration as well as deposition of hydrothermal sulfides in the near surface zone of the sediments a second major discovery at site 1038 was the evidence for fluid phase separation at depth at temperatures possibly in excess of 400 c this conclusion is based on the presence of both low cl and high cl fluids the latter appear to be advected rapidly towards the surface presumably along cracks and faults the low cl fluids however appear to be transported laterally along sandy horizons in the sediments thus signifying two very different migration pathways for high cl and low cl hydrothermally phase separated fluids studies of the organic geochemistry of dissolved gases and matured organic matter corroborate these findings of extensive hydrothermal alteration of the sediments

free and sulphurized hopanoids and highly branched isoprenoids in immature lacustrine oil shales abstract a study of the solvent extracts of four samples from two immature oil shales from tertiary lacustrine basins ribesalbes and campins southern european rift system deposited under reducing conditions has allowed the identification of s containing hopanoids and novel highly branched isoprenoids hbi hbi derivatives occur only in the ribesalbes shales where two new structural types of c 25 s containing hbi isomers have been identified these compounds probably have different precursor organisms from those in recent marine systems they are present as thiophenes thiolanes and thiolane sulphoxides in one case and only as thiolanes in the other 17 21 h 17 21 h and 17 21 h thienyl and methylthienylhopanes have been found in the shales from the two basins in the campins samples these compounds occur together with thiolanyl and methylthiolanylhopanes distributions of 17 21 h and 17 21 h hopanes hop 17 21 enes and 2 methylhop 17 21 enes ribesalbes only are also encountered comparison of the hopane distributions from both solvent extractable aliphatic and thiophene fractions and the sulphur and oxygen bound macromolecular matter in ribesalbes basin shows a remarkable similarity between all fractions this resemblance points to rather uniform inputs and depositional processes for the accumulation of these compounds both as small molecules or bound to macromolecules e g early bonding of bacteriohopanepolyols to sulphur and to the macromolecular organic matter the good correlation among the macromolecular fractions in ribesalbes basin is reinforced when comparing the 13 c composition of phytane c 20 and c 25 hbi and the c 35 hopane homologues in the different fractions

the palaeoenvironmental and palaeohydrological evolution of padul peat bog granada spain over one million years from elemental isotopic and molecular organic geochemical proxies abstract the elemental concentration of organic carbon atomic h c and c n ratios isotopic 13 c values of organic matter and molecular predominant n alkane chain length and carbon preference index cpi organic components were measured for 600 samples taken from a 107 m long core from the padul basin andalusia spain the record runs from the lower pleistocene ca 1 ma b p to the mid holocene ca 4 5 ka b p with in general little diagenesis removal of components two markedly different hydrogeological scenarios were interpreted 1 from ca 1 ma to ca 400 ka b p run off recharge was significant and water depths were greater lacustrine scenario from ca 400 to 4 5 ka b p the padul basin became a peat bog s s with the major water input coming from groundwater inflow from ca 400 to ca 180 ka b p alternating episodes with either predominant grasses trees or aquatic macrophytes which were linked to wet dry phases took place an important deglaciation episode has been interpreted to occur between ca 180 and 170 ka b p the global climatic changes occurring from ca 170 to 25 ka b p were not recorded in the proxies though they do show important variations linked to the last glacial maximum and the beginning of the holocene ca 25 10 ka b p 2 cold phases coexisting with dry periods produced the recession of forests and the development of grasses after these periods as both temperature and precipitation increased forests expanded and the water level linked to thaw rose especially at ca 20 ka b p few changes occurred during the holocene although there were short alternations between wet and dry episodes overall the techniques applied proved to be excellent palaeoenvironmental proxies for studying the basin s palaeoclimatological and palaeohydrological evolution

environmental changes recorded in the holocene sedimentary infill of a tropical estuary abstract early to late holocene sedimentary infill of the potengi jundiai estuary brazil was studied in a 31 5 m long sediment core the borehole was drilled in a mangrove area within the central part of the flood tide delta the sedimentary record encompassing the last 10 kyr was studied for sediment texture and for the n alkanes composition of organic matter om sediments rich in om and bivalve shells accumulated during the period of sea level rise mostly in an intertidal environment of mangrove forest mudflat and subtidal estuarine flood delta the characterization of n alkanes c10 c33 and lignin methoxyphenols by means of direct analytical pyrolysis py gc ms technique allowed determining the sources of the extant om downcore fluctuations were observed in n alkanes and in several n alkane based indices such as long chain carbon preference index cpi c24 c33 long to short chain ratio l s and average chain length acl as well as in the relative proportion of lignin derived compounds the n alkanes distribution points to changing sources of om input to the estuarine sediments over most of the holocene period major inputs of terrestrial vegetation alternated with periods of mixed input from aquatic macrophytes as the rate of sea level rise changed over time the n alkanes distribution and the lignin markers were useful for reconstructing paleoenvironmental conditions particularly during the early holocene when the lower potengi river valley now an estuarine area could accommodate terrestrial forest vegetation before switching to halophytic mangroves as sea levels rose

saturated and olefinic hydrocarbons in recent sediments from the baltic sea abstract saturated and olefinic hydrocarbons in the top sections of contemporary sediments from four stations in the baltic sea teili 1 f 81 eb 1 and xv 1 were analysed by capillary gas chromatography and gc ms techniques the 0 2 2 4 4 5 and 10 11 cm sections showed a small unresolved complex mixture ucm however in all these sections a strong predominance of odd over even carbon numbered compounds exists indicating an insignificant petroleum hydrocarbon input in the areas studied the resolved hydrocarbons are of mixed marine autochthonous and terrigenous origin the 0 5 cm sections contained the highest proportions of short chain and branched chain hydrocarbons derived mostly from algae and bacteria in general an increase was observed in the ratios of saturated to unsaturated and of longer chain to short chain hydrocarbons with increasing depth because of the facile diagenesis of unsaturated components and faster biodegradation of short chain hydrocarbons in addition between one and seven hydrocarbons the exact structure of which could not be assigned were detected in the samples most of these components were cyclic and unsaturated and a number were triterpenes

lipid biomarkers in lacustrine sediments of subtropical northeastern mexico and inferred ecosystem changes during the late pleistocene and holocene abstract evolution of ecosystems in the northeastern mexico since the last glacial maximum lgm and through the holocene are yet to be fully characterised creating a gap in our understanding of the ecological response to climate change in this water scarce region here we explore the response of lacustrine and surrounding terrestrial habitats of this region to hydrological changes of the late pleistocene and especially the holocene biomarker based proxy data from the el potosi basin indicates dynamic and variable input of organic matter om into the basin with sources being the surrounding vegetation bacterial biomass and aquatic microfauna changes in these inputs reveal distinct stages of ecosystem development over the last 20 000 years overall low lipid abundances as a proportion of toc from 20 to 19 cal kyr bp mainly from aquatic in situ microbial biomass and degraded terrestrial om are attributed to relatively low runoff increasing lipid proportions during the deglaciation from 19 to 15 cal kyr bp were mostly derived from terrestrial sources like woodland vegetation soil and wetland vegetation and we attribute them to more rainfall and runoff subsequently the wetland biomarkers disappeared and woodland input began to dominate the om assemblage from 15 to 11 7 cal kyr bp during the early and mid holocene after about 11 7 cal kyr bp putative woodland and grass inputs decreased and the dominant vegetation appeared to shift to subtropical desert shrub which could have been due to increasing regional aridity the onset of the dry late holocene was characterised by gradual environmental transition and ecosystem adaption especially from 4 2 to 2 8 cal kyr bp the terrestrial vegetation comprised increasing proportions of c4 grasses documented by changes in leaf wax carbon isotopic compositions and potentially more open vegetation while the in lake bacterial production increased with increasing desertification from 2 8 cal kyr bp the terrestrial productivity decreased substantially the lake became shallower ephemeral and the surrounding soils became more alkaline changes of the limnic habitat from algal towards microbial communities occurred 300 years after the onset of terrestrial habitat changes during the last millennium the c3 components of the vegetation again dominated this implies an enhanced moisture supply possibly from agricultural activities overall this work reveals the marked sensitivity of northeastern mexico ecosystems to the climatic shifts that occurred since the lgm and this perhaps indicates their vulnerability to future global warming

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

unusual distribution of hydrocarbons in a hydrothermally altered phosphorite nodule from kusu basin northern kyushu japan abstract lacustrine phosphorite nodules occur in diatomaceous mudstone from the kusu basin northern kyushu japan most of these phosphorite nodules have been hydrothermally altered features of the extractable hydrocarbons in an altered nodule are n alkanes with an even carbon number predominance and unusual suites of dimethyalkanes and alkylcyclopentanes maturity indicators based on hopanes show that this non altered sample is much more mature than a hydrothermally altered one the hydrocarbons in the altered phosphorite were produced during the alteration process and dimethylalkanes and alkylcyclopentanes can be regarded as specific biological markers for hydrothermal environments

palaeozoic oil source correlation in the tarim basin nw china a review abstract oil source correlation in the cratonic region of the tarim basin nw china has long been controversial current knowledge of the potential source rock distribution end member selection oil source correlation and impacts of secondary alteration processes have been reviewed two source rock systems from the cambrian lower ordovician o 1 and middle upper ordovician o 2 3 potentially contributed to oil accumulations in the cratonic region geochemical correlations suggest that oils are dominantly derived from the o 2 3 source rocks while geological evidence and sulfur isotopic compositions supports the o 1 source rocks as a main contributor such inconsistency is rooted in the selection of end members and their characterization changes in some biomarker parameters such as sterane distribution gammacerane index and ratio of tricyclic terpanes to pentacyclic terpanes are mainly controlled by thermal maturation and biodegradation rather than source input and depositional environment variation no clear boundary between the two source systems can be established using biomarkers except for a few diagnostic components some o 1 source signatures such as even odd predominance of n alkanes unusual tricyclic terpane distribution unusually enriched 13 c carbon isotopic compositions of oils and kerogens and the occurrence of combustion related polycyclic aromatic hydrocarbons largely result from an abnormal heating influence either from igneous intrusion or hydrothermal fluid activity local thermochemical sulfate reduction can also remove most source related signatures these so called markers in currently selected end members result from extensive secondary alteration processes and do not reflect source input differences while more research is needed for full reconstruction of oil source correlation in the cratonic region of the tarim basin the main source rocks most likely reside in the o 1 succession rather than o 2 3

organic geochemical evidence of late pleistocene holocene environmental changes in the lake balaton region hungary abstract this paper presents organic geochemical records and a combined interpretation of organic geochemical and palaeoecological data for a late pleistocene holocene shallow lake sequence abundance bulk chemical composition and sources of the organic matter om as well as the relative contribution of the labile and resistant bio and geo macromolecules were determined on 46 sediment samples lipids isolated from selected samples representing the lowest and highest water levels were analyzed integration of the organic geochemical and palaeoecological records suggests that climate exerted the primary control on the amount and quality of the om preserved the relative contribution of the labile fresh plant and litter and resistant lignin and cellulose bio macromolecules immature geo macromolecules humic substances and mature refractory geo macromolecules and the degree of preservation of the primary biomass calculated from mathematical deconvolution of rock eval pyrograms allowed the distinction of three and five zones related mainly to water level fluctuation within the late pleistocene and holocene sequences respectively

sources dispersal and preservation of sedimentary organic matter in the yellow sea the importance of depositional hydrodynamic forcing abstract the sources distribution and fate of sedimentary organic matter som in the yellow sea ys were studied based on the datasets of total organic carbon toc total nitrogen tn organic carbon isotopic values 13 c and n alkanes of forty seven surface sediment samples the spatial pattern of toc and tn coincided with that of the sediment grain size suggesting the hydrodynamic constraints on the accumulation of som in the ys the relatively low toc tn ratios with contrasting tn intercept of the regression lines indicate the influence of the sorption of inorganic n in the nys and a mixture of microorganism derived n rich om pool with the terrigenous n poor om for the sys sediment samples respectively the enriched 13 c could also be partially related to the agriculture inputs due to the enhanced fertilization process in addition to the planktonic derived om molecular compositions of n alkanes and principal component analysis pca showed a significant terrigenous contribution for the som in the central mud deposits the observed even carbon preference of the short chain length n alkanes c 12 c 22 reveals the potential contribution of microorganism derived om in the ys combined lines of evidence of significant terrigenous n alkanes in the ys suggest that the hydrodynamic forcing plays a key role on the selective dispersal and preferential accumulation of the fluvial terrigenous organic materials the simplified terrigenous som transport pathway to the central mud deposits of the ys was conceptually constructed based on the mixed sediments provenances hydrodynamic transport and depositional mechanism of the fine grained sediments in this region

comparative 14c and osl dating of loess paleosol sequences to evaluate post depositional contamination of n alkane biomarkers there is an ongoing controversial discussion as to whether n alkane lipid biomarkers and organic matter of loess in general reflect a synsedimentary paleoenvironmental climate signal or whether they are significantly affected by postdepositional contamination for example related to root and rhizomicrobial activity in order to address this issue at our study site the middle to late weichselian loess paleosol sequence gleina in saxony germany we determined and compared radiocarbon ages of bulk n alkanes and sedimentation ages as assessed by optically stimulated luminescence osl dating the bulk n alkanes of the four dated samples yielded calibrated 14c ages ranging from 24 1 to 49 7 cal ka bp 95 4 probability ranges while the three uppermost n alkane samples are well within the range or even slightly older than the osl inferred sedimentation ages the lowermost n alkane sample is slightly younger than the osl ages there is hence little or no evidence at our study site for n alkanes in loess paleosol sequences being significantly contaminated by deep subsoil rooting or microbial processes we propose a 14c isotope mass balance calculation for estimating such contaminations quantitatively radiocarbon dating of bulk n alkanes might have great potential for quaternary research and we encourage further comparative 14c and osl studies

origin and distribution of biomarkers in the sulphur rich utrillas coal basin teruel mining district spain abstract the utrillas coal facies are located in the maestrazgo basin in ne spain this mining district of teruel contains sub bituminous deposits from the middle albian lower cretaceous 105 ma in areas near a delta estuary with abundant sulphur the high sulphur content is due to an influx of sulphate caused by the geological recycling of triassic gypsum from the catchment area into the delta estuary in some outcrops the weathered coal reveals leonardite deposits the depositional environment of the basin originated coals some of which are currently mined the organic matter of the coals has been the object of scattered reports studies have focused on bulk pyrolysis parameters and microscopic observation in utrillas samples as well as the inorganic and insoluble organic fraction we analysed the organic soluble extract of the utrillas coals using gc ms in order to characterize their aliphatic aromatic and organosulphur compounds the biomarker distribution allowed us to recognize different inputs assess their depositional palaeoenvironment and finally determine their degree of maturity in particular homologous series of hopanes related to eubacteria were present biomarkers characteristic of higher plant inputs were also widely distributed e g phyllocladane or c 29 steranes the presence of linear alkylbenzenes allowed us to recognize the palaeodepositional reducing environments where they were deposited specifically thienylhopanes were associated with sulphur reducing environments finally the abundance of unsaturated biomarkers such as diacholestenes indicated low maturity coals various aromatic ratios such as the methylphenanthrene index also suggested diagenesis in the initial stage

do the large carbon isotopic excursions in terrestrial organic matter across paleocene eocene boundary in india indicate intensification of tropical precipitation abstract five distinct transient warming hyperthermal events paleocene eocene thermal maximum petm h1 etm2 elmo h2 i1 and i2 marked by negative carbon isotope excursions cies occurred between late paleocene and early eocene 56 to 52 ma interval however not many records of either the petm or definitive early eocene hyperthermals eehs are yet available from terrestrial realm in the tropics except two neo tropical sections of colombia and venezuela jaramillo et al 2010 therefore response of the tropical biosphere to these warming events is not very well known here we report high resolution carbon isotope 13c chemostratigraphy biomarker calcareous nannofossils and pollen data from the cambay shale formation of western india paleolatitude 5 s which show complete preservation of all the above cie events including the petm hitherto unknown from tropical terrestrial record comparatively larger magnitudes of cies for all the hyperthermal events the petm and eehs point towards a possible intensification of precipitation during the petm and all the early eocene hyperthermal cie events this inference is supported by data of lignin phenols and presence of tropical rain forest elements spanning the entire time period 56 52 ma and suggest that higher organic burial and soil erosion favored deposition of thick lignitic seams as a consequence of high tropical precipitation

geochemistry of fluid phases and sediments relevance to hydrothermal circulation in middle valley odp legs 139 and 169 geochemical and isotopic studies of pore fluids and solid phases recovered from the dead dog and bent hill hydrothermal sites in middle valley ocean drilling program leg 169 have been compared with similar data obtained previously from these sites during ocean drilling program leg 139 although generally the hydrothermal systems reflect non steady state conditions the data allow an assessment of the history of the hydrothermal processes sediment k al ratios as well as the distribution of anhydrite in the sediments suggest that the dead dog hydrothermal field has been and still is active in contrast similar data in the bent hill hydrothermal field indicate a waning of hydrothermal activity pore fluid and hydrothermal vent data in the dead dog hydrothermal field are similar in nature to the data collected during odp leg 139 in the area of the bent hill sulfide deposit however the pore water data indicate that recent wholesale flushing of the sediment column with relatively unaltered seawater has obliterated a previous record of hydrothermal activity in the pore fluids data from the deepest part of hole 1035a in the bent hill locality show the presence of hydrothermal fluids at greater depths in this area this suggests the origin of the hydrothermal fluids found to be emanating from hole 1035f which constitutes one of the first man made hydrothermal vents in the middle valley hydrothermal system similarly corked hole 858g because of seal failures has acted as a hydrothermal vent with sulfide deposits forming inside the cork

geochemistry of shallow sediments in guaymas basin gulf of california hydrothermal gas and oil migration and effects of mineralogy offset of prograde hydrothermal alterations by retrograde reactions is evident in sediments from a piston core pc6 8 m long from the guaymas basin gulf of california geochemical and mineralogical analyses of sediments and pore fluids show superimposed geochemical signals that indicate currently active reactions are modifying previously formed secondary solids hydrothermal barite was formed in a previously active flow channel between 150 and 250 cm depth hydrothermal gypsum is presently dissolving at depths 780 cm below which hydrothermal fluid flow is channeled by a secondary dolomite layer thermal stress of organic matter generates hydrothermal gas and petroleum having wide ranges of compositions and maturities a significant amount of hydrothermally generated oil has been transported laterally through a porous debris flow approx 240 cm subbottom overwhelming the indigenous bituminous matter water soluble petroleum constituents have disseminated throughout the cored sediments from 400 to 700 cm depth the immature organic matter continues to experience thermally enhanced diagenesis and an even higher thermal stress has occurred at the bottom of the core enhanced bacterial degradation of organic matter has led to depletion of pore water sulfate and enrichment of ammonium nh4 in both pore fluid and sediment resulting in formation of nh4 bearing secondary clay minerals at depths below 780 cm

organic geochemistry across the permian triassic transition at the idrijca valley western slovenia abstract bulk and molecular stable c isotopic compositions and biomarker distributions provide evidence for a diverse community of algal and bacterial organisms in the sedimentary organic matter of a carbonate section throughout the permian triassic p tr transition at the idrijca valley western slovenia the input of algae and bacteria in all the upper permian and lower scythian samples is represented by the predominance of c15 c22 n alkanes odd c number alkylcyclohexanes c27 steranes and substantial contents of c21 c30 acyclic isoprenoids the occurrence of odd long chain n alkanes c22 c30 and c29 steranes in all the samples indicate a contribution of continental material the decrease of corg and ccarb contents increase of rock eval oxygen indices and 13c enrichment of the kerogen suggest a decrease in anoxia of the uppermost permian bottom water the predominance of odd c number alkylcycloalkanes c27 steranes and c17 n alkanes with 13c values 30 and 13c enrichment of the kerogens in the lowermost scythian samples are evidence of greater algal productivity this increased productivity was probably sustained by a high nutrient availability and changes of dissolved co2 speciation associated to the earliest triassic transgression a decrease of corg content in the uppermost scythian samples associated to a 13c depletetion in the carbonates up to 4 and individual n alkanes up to 3 4 compared to the upper permian samples indicate lowering of the primary productivity algae cyanobacteria and or higher degradation of the organic matter

late quaternary environmental change record in biomarker lipid compositions of lake ebinur sediments northwestern china late quaternary paleoclimate records from arid regions help us understand the response of ecological systems to natural climate change to place recent changes in a longer term perspective in this research a biogeochemical analysis of a sediment core from lake ebinur xinjiang allowed us to infer the climate and environmental changes in the late quaternary in arid northwestern china the combined lipid biomarkers and bulk biogeochemical properties toc 13corg revealed moderately wet conditions from 34 to 28 ka favoring the growth of terrestrial vegetation the subsequent period from 28 to 13 ka was dominated by aquatic plants algae and microbes indicating cold and dry conditions ameliorated regional moisture conditions were deduced from the higher carbon preference index cpi and from 13corg values from 13 to 3 6 ka the optimum climate conditions occurred from 9 to 5 ka several climatic events also exist in the lake ebinur records with a wide distribution into other regions our biogeochemical based paleoclimate and paleoenvironmental reconstruction is generally synchronous with sedimentary records from mid latitude eurasia and the ngrip ice core record which probably has a certain linkage with the 45 n summer insolation we propose that summer insolation conditions in the northern hemisphere might have an impact on the climate and environmental changes in arid northwestern china in the late quaternary

biogeochemistry of the 1640 ma mcarthur river hyc lead zinc ore and host sediments northern territory australia abstract the formation of the mcarthur river lead zinc deposit involves thermogenic or biologic oxidation of sedimentary organic matter the products of which generated a massive stratiform sulfide ore body and secondary carbonate and silica precipitates formed within the sediment pile down the flow pathway and above the reaction zone the fine grained texture of the mineralization indicates that primary ore texture is preserved and coupled with the regional thermal maturity indicate that this deposit is an ideal location to study organic matter signals related to ore formation and the sedimentary environment biomarker data point to a marine environment of deposition and are consistent with data previously collected from the host barney creek formation in the adjacent glyde subbasin an unusual biomarker distribution found in some samples from within two orebody is considered to be related to the presence of sulfide oxidizing bacteria these organisms flourished after turbidite deposition when oxygen in the upper part of the water column was mixed down to the sediment water interface the biomarker data are supported by micropalaeontologic observations from the same samples and are consistent with intermittent oxygenation of the water column to the sediment water interface this observation suggests an extension of the known occurrence of sulfide oxidizing bacteria back in time by 800 million years to 1640 ma

possible origin of n alkanes with a remarkable even to odd predominance in recent marine sediments abstract n alkane distributions with a remarkable even to odd predominance c16 c24 were found in marine surface sediments the previously proposed diagenetic reduction of the corresponding n fatty acids could not be considered as a source for these n alkane based on a comparison of compositional features of n alkane n fatty acid and n alcohol distributions carbon isotope analyses and other geochemical parameters the data indicate that the even predominant n alkanes were derived directly from marine bacteria

hydrothermal petroleum generation in red sea sediments from the kebrit and shaban deeps abstract petroleum impregnated sediments and massive sulfides have been found in two deeps of the northerns red sea biological marker distributions in extracts and polar fraction degradation products were analyzed in order to elucidate the source of the petroliferous material two organic phases could be distinguished according to their source and maturity the amounts of n alkanes show a marked decrease with depth whereas the concentrations of various branched and cyclic hydrocarbons increase resulting in a humpof unresolvable compounds in a depth as shallow as 300 cm changes in concentrations and distributions of hopanoids in the kebrit deep sediments indicate a rapid increase of maturity with depth the deepest core section 300 cm and the masive sulfide reveal comparable maturation indices typical for mature oils by chemical degradation of the polar fractions a series of c 40 isoprenoids was obtained which reveals a considerable contribution from methanogenic and thermophilic archapbacteria to the immature organic matter the data suggest that petroliferous material ofthermogenic origin migrates through the younger sequences superimposes the autochthonous organic substances in the sediments and furthermore forms asphaltic impregnations in the massive sulfides

application of organic facies and biomarkers in characterization of paleoenvironmental conditions and maturity of sediments from the codo formation in the west central part of the sao luis basin brazil abstract paleoenvironmental conditions of the sediments of the cretaceous codo formation in brazil are still being debated the main point of controversy is whether they were deposited in a strictly marine environment or under lacustrine conditions of varying salinity in this study organic facies and biomarker analyses were performed on samples from the codo formation in the sao luis basin northwest brazil to reconstruct the paleoenvironmental conditions the origin and the thermal maturity of the organic matter four types of palynofacies associations pi amorphous organic matter pii amorphous organic matter sporomorphs piii phytoclasts and iv marine palynomorphs were identified the total organic carbon toc content exhibits a strong correlation 0 75 p 80 the thermal maturity indicators including vitrinite reflectance ro spore color index sci ts ts tm ratios and c29 20s 20s 20r and c29 indicate that the organic matter is immature to marginally mature

an isotopic biogeochemical assessment of shifts in organic matter input to holocene sediments from mud lake florida abstract a molecular and isotopic study of sediment cores from a sinkhole lake mud lake florida usa was performed in order to relate documented changes in the regional terrestrial vegetation and water table over the last 5500 years to molecular and isotopic proxies for biological sources of organic matter to the lake sediments temporal shifts in the source of organic matter to the sediment as determined by the stable carbon isotope composition of bulk organic matter and biomarkers correspond with previously defined regional scale transitions in forest ecosystems quercus to pinus at 5500 14 c yr bp and taxodium expansion at 2500 14 c yr bp and coincident increases in the floridan water table the 13 c values for total sedimentary organic carbon showed a shift from terrestrial and aquatic macrophyte sources 27 8 in sediments dated at 5400 14 c yr bp within the basal peat to a cyanobacterial dominated sapropel 18 1 at the surface a comparison of the 13 c values of bulk sediment and biomarkers representative of cyanobacterial and algal input e g 7 and 8 methylheptadecane and the n alkane c 17 indicates that the present shallow lake was fully developed by 2400 14 c yr bp differences among the 13 c values of specific biomarkers derived from vascular plants c 29 and c 31 n alkanes and cuo lignin oxidation products and from cyanobacteria and algae are nearly equivalent in magnitude to the shift recorded in 13 c of toc indicating their effective use as source proxies in this system

biogeochemical characterization of particulate organic matter from a coastal hydrothermal vent zone in the aegean sea abstract three particle interceptor traps were moored from june to september 1996 along the se coast of milos island aegean sea in an area known for its extensive seabed geothermal activity the settling particles collected differed between sites not only in quantity but also in their geochemical composition in the area directly influenced by warm water vents the vertical flux of particulate material was almost one order of magnitude higher than that observed at the reference sites 6 5 km away from the vents with a higher contribution of biogenic material in the former the neutral lipid fractions exhibited a significant zooplankton biomarker signature e g cholesterol and wax esters followed by those of microalgal and terrigenous remains the biogeochemical cycle of sterols included the formation of steroidal ketones thiols and stanols the latter two particularly associated with the venting activity moreover the aliphatic and aromatic hydrocarbons in the particles from the venting area reflected a locally enhanced maturity of the organic matter although part of the material collected in the traps may have been exported in the vent waters the higher fluxes observed in the vicinity of the hydrothermal plumes are mainly the result of an assemblage of zooplankton which in turn may contribute significantly to the sedimentation through fast sinking faecal pellets of the petrogenic hydrocarbons possibly generated in the vents

synchronous change of temperature and moisture over the past 50 ka in subtropical southwest china as indicated by biomarker records in a crater lake abstract over the past few decades studies on the indian summer monsoon ism have been mainly based on paleo marine records whilst the sparsity of land records limits our understanding of the ism evolutionary process over continental landscapes here we provide paleoclimate reconstructions based on n alkanes and branched glycerol dialkyl glycerol tetraethers brgdgts from a 50 ka lacustrine sediment core collected from lake tengchong qinghai in southwestern subtropical china our results reveal that the botanical sources of sedimentary n alkanes in this lake are mainly from aquatic macrophytes and terrestrial plants the lake level evolution from the mis 3 to the holocene can be divided into four stages high in the mis 3 low in the lgm high in last deglacial and low in mid and late holocene our brgdgts based climate reconstructions indicate that the mean air temperature differences between the present day and the lgm were up to about 3 4 c from mis 3 to holocene there was a broadly and consistently synchronous trend between precipitation and air temperature in this ism region this is different from the asynchronous temperature and precipitation variations in the east asian summer monsoon easm regions in the period of last glacial termination our study shows that the climate in ism regions was primarily driven by changes in june summer solar insolation at 30 n and those glacial boundary conditions such as ice volume and sea surface temperature might also have affected the ism

n alkanes as indicators of climate and vegetation variations since the last glacial period recorded in a sediment core from the northeastern south china sea scs abstract variations in n alkanes proxies l h c31 c27 and acl molecular abundances of n alkanes and stable carbon isotopic compositions of n alkanes 13calk from the core std235 20 21 15 n 118 22 56 e have been used to trace characterize the climatic changes that occurred in the northern south china sea scs during the last glacial period the ratio of low to high molecular weight n alkanes l h and the concentration of n alkanes indicated that organic matters in the sediments were derived from the mixture of both marine and terrestrial sources but dominated by marine autochthonous input over the past 20 ka total n alkanes were higher during the last glacial stage relative to the interglacial stage implying the low sea level and the strengthened east asian winter monsoon eawm during the glacial time the 13calk data indicated that the terrestrial plants on the adjacent continent of the present study area were dominated by c3 plants during the holocene and experienced the expansion of c4 plants during the last glacial period this similar result can be proved by the chain length parameter of n alkanes c31 c27 acl and the content of the herb pollen in addition n alkanes distributions and c4 vegetation proportion calculated by 13c of long chain n alkanes in the core std235 recorded a short arid duration paralleled by the heinrich event 1 thereby we deduced that the occurrence of the dry event and the variation of regional vegetation community at the adjacent lands of the northern scs were likely under the influence of the climate change emanated from the boreal high latitudes

aliphatic hydrocarbons in coastal sediments of the northern cyprus eastern mediterranean the sources and spatial distributions of aliphatic hydrocarbon concentrations were investigated in surficial sediments of the northern cyprus gemi konagi girne and gazi magusa areas aliphatic hydrocarbon levels were determined with a gas chromatography mass spectrometer total aliphatic hydrocarbon n alkanes 25 isoprenoids 2 concentrations in the sediments were found in the range of 1107 6360 ng g results indicated that the sediments were mainly dominated by odd numbered n alkanes n c10 n c34 maximizing at n c17 n c29 and n c31 statistical analyses and diagnostic ratios have been used to determine the possible sources and origins of aliphatic hydrocarbons aliphatic hydrocarbons were showed biogenic character at all sampling areas and were found mainly originated from terrestrial marine and both terrestrial marine plants at gemi konagi gazi magusa and girne respectively

age and origin of the well preserved organic matter in internal sediments from the silesian cracow lead zinc deposits southern poland the molecular and petrographic characteristics of organic matter in internal sediments from the mississippi valley type lead zinc deposits in southern poland reveal immature and well preserved organic matter huminite reflectance values of organic matter in all internal sediments are low with a mean value of 0 29 corresponding to a lignite range of coalification most organic compounds in the organic matter e g cadalene retene simonellite perylene and sitosterol and its transformation products stigmastanol and stigmasta 3 5 dien one as well as lignin degradation compound products e g benzoic acid vanillin 4 benzaldehyde benzenedicarboxilic acids and hydroxybenzoic acids are of terrestrial origin monosaccharides with dominant and glucose were identified as possible remnants of cellulose degradation products suggesting an excellent state of organic matter preservation given that monosaccharides are preserved only under conditions of limited oxygen after sedimentation resulting from the rapid accumulation of internal sediments in meteoric paleokarst cavities followed by insignificant diagenesis petrologic and palynological data on internal sediments clearly indicate a middle triassic age for organic matter and for the development of a triassic meteoric karst system immediately after anisian carbonate sedimentation

a statistical approach to the interpretation of aliphatic hydrocarbon distributions in marine sediments abstract q mode factor analysis was used to quantitate the distribution of the major aliphatic hydrocarbon n alkanes pristane phytane systems in sediments from a variety of marine environments the compositions of the pure end members of the systems were obtained from factor scores and the distribution of the systems within each sample was obtained from factor loadings all the data from the diverse environments sampled estuarine san francisco bay fresh water san francisco peninsula polar marine antarctica and geothermal marine gorda ridge sediments were reduced to three major systems a terrestrial system mostly high molecular weight aliphatics with odd numbered carbon predominance a mature system mostly low molecular weight aliphatics without predominance and a system containing mostly high molecular weight aliphatics with even numbered carbon predominance with this statistical approach it is possible to assign the percentage contribution from various sources to the observed distribution of aliphatic hydrocarbons in each sediment sample

alkane distributions in arctic ocean sediments reply to alkane and pah biomarkers as tracers of terrigenous organic carbon in arctic ocean sediments by mark b yunker robie w macdonald lloyd r snowdon brian r fowler comment by vera petrova and co authors

a synthesis of hydrogen isotope variability and its hydrological significance at the qinghai tibetan plateau abstract hydrogen isotope ratios of sedimentary biomarkers are known to record the climatic variability in terrestrial and marine environments however there is still a lack of calibration studies that can quantitatively retrace the driving forces especially at the tibetan plateau here we elaborate the actual influence of environmental parameters such as temperature evapotranspiration salinity and biosynthetic fractionation on d values of n alkanes we measured hydrogen isotope values d of n alkanes in recent sediment and plant samples as well as d values of different water sources lake and inflow water precipitation as well as leaf root and soil water from six tibetan lakes along a 10 spanning longitudinal transect covering an aridity gradient as expected the deuterium record can be used to distinguish two water pools at the plateau i precipitation water which supplies water for the lake inflow and terrestrial plants and ii enriched lake water having a clear evaporative signal based on significant correlations of the source water and d values of n alkanes d of alkane n c 23 record the lake water isotope composition and track the evaporative enrichment of the lake system in contrast d of alkane n c 29 can be used to retrace the isotope composition of the inflow displaying the integrated rainfall signal in the vegetation period modified by soil and leaf water evaporation while temperature changes are less pronounced across the tibetan transect the isotopic difference between c 23 and c 29 could potentially be used as a proxy to reconstruct effective moisture precipitation minus evaporation areas with lower precipitation amounts and higher evaporation rates are characterized by higher d c 23 c 29 values this relationship is more pronounced in regions with mean annual precipitation below 350 mm even in contrasting environments the application of the d proxies is very promising combining other tibetan studies it is possible to present a comprehensive picture of the usage of compound specific hydrogen isotopes of n alkanes on the tibetan plateau

quantification of low molecular weight n alkanes in lake sediment cores for paleoclimate studies abstract organic biomarkers such as n alkanes can be used as proxies in a range of paleoclimate and paleoenvironmental investigations n alkanes accumulate in lacustrine sediments and can therefore be used to determine past terrestrial conditions by investigating chain length ratios and compound specific isotope signatures analytical methods for their quantification in sediments have been described previously however method validation has not been rigorously reported for the low molecular weight lmw n alkanes which have recently been gaining attention as useful proxies using spike and recovery experiments with a simple sand matrix we found that lmw n alkanes are prone to low recovery due to volatilization when following common protocols for quantification this is alarming because low recovery can lead to misinterpretation of n alkane results on the other hand we found that isotope fractionation was fortunately not observed even when volatilization loss was high we addressed the problem of lmw n alkane volatilization by developing an alternative extraction and sample preparation method the optimized method which employs pressurized liquid extraction was tested by using it to extract n alkanes from sediments from three southern new zealand lakes hinemoa ohau and thomas with different properties recovery of the c15 c40 n alkanes ranged from 32 66 for lake hinemoa 54 85 for lake thomas and 61 89 for lake ohau variation in n alkane recovery from the three lakes was attributed to differences in sediment properties notably organic matter and particle size and an approach for calculating adjusted concentration with a sediment specific adjustment factor for each n alkane is suggested

an examination of the fidelity of n alkanes as a palaeoclimate proxy from sediments of palaeolake tianyang south china this study examines n alkane distributions from a 120 m long borehole extracted from palaeolake tianyang south china which covers the last five glacial cycles we aim to determine the palaeoclimatic environmental fidelity of n alkane distributions in bulk organic matter om from this tropical sedimentary archive the tianyang lithostratigraphy reveals a deep lake sequence 120 42 m dominated by diatomite overlain by shallow lake and marsh sediments in the upper 42 m the carbon preference index cpi c23 c31 suggests that there is weak odd even predominance oep in long chain n alkane distributions c27 c31 in om from deep lake sediments and a strong oep of long chain n alkane distributions in om from shallow lake sediments the opposite characteristics are evident in short chain n alkane distributions c16 c20 these cpi values suggest different sources of organic carbon within the deep dominantly diatom synthesis and shallow lake dominantly high plant input but cannot help differentiate glacial from interglacial sediments the terrigenous to aquatic ratio tar shows high values throughout interglacial sediments 4 and low values in glacial sediments 4 corresponding to a higher productivity of high plants during interglacials and vice versa the proportion of aquatic plant n alkanes paq also reveals a clear change between glacial 0 31 0 39 and interglacial periods 0 22 0 28 during shallow lake stage indicating a reduction in terrestrial om input during glacial periods relative to interglacial periods there is a greater amount of unresolved complex mixture ucm in glacial sediments than within interglacial sediments we suggest that the above n alkanes indexes are useful environmental climatic indicators within palaeolake tianyang despite the fact that some other indexes like average chain length acl provide less definitive interpretations

hydrothermal alteration of organic matter in sediments of the northeastern pacific ocean part 1 middle valley juan de fuca ridge samples from the ocean drilling program leg 169 in middle valley ne pacific ocean were analyzed to study maturation by accelerated diagenesis and catagenesis of the sedimentary organic matter to hydrothermal petroleum some data from site 858 in middle valley leg 139 are also discussed for completeness sediments at sites 858 and 1036 in middle valley were altered either by the full variety of high temperature fluids which generated hydrothermal petroleum or by accelerated thermal diagenesis of the immature organic matter in situ without specific migration of those petroleum bitumen products the hydrothermal petroleums from the deeper sediments have migrated and accumulated in discrete intervals at shallower depths within a contemporary temperature window of 60 135 c at both of these sites maturation for the n alkanes proceeded from high cpi values immature to 1 0 mature i e strong even c number preference due to their low toc contents these sediments did not generate high amounts of hydrocarbons from the kerogen and thus revealed this unique even c number preference furthermore the significant content of terrestrial organic matter yielded petroleums low in gas and volatiles biomarkers were converted from the biological natural product precursors to the geological derivatives with maturities reflecting the thermal stress high temperature alteration also yielded polynuclear aromatic hydrocarbons

effect of lake evaporation on δd values of lacustrine n alkanes a comparison of nam co tibetan plateau and holzmaar germany compound specific hydrogen isotope ratio values of lacustrine n alkanes from two contrasting ecosystems the semiarid to arid nam co central tibet and the humid holzmaar germany were compared in order to assess whether or not these environmental conditions are recorded in the isotopic signatures of biomarkers increased evaporation of lake water at nam co is recorded by the n alkanes of aquatic origin hence isotopic enrichment results in a di erence between terrestrial and aquatic n alkanes in the opposite direction 68 from that known for humid climate conditions 30 predominating at holzmaar based on this isotopic di erence between terrestrial and aquatic n alkanes evaporation to inflow ratio e i values were estimated and suggest that the isotopic di erence is indicative of the general hydroclimatic characteristics of a lake system moreover the comparison with e i values calculated with actual stable water isotope data showed that the dd values of aquatic and terrestrial lacustrine n alkanes serve as a proxy for the relative isotopic di erences between lake and inflow waters and can be used to assess the proportion of water undergoing evaporation relative to the inflow and thus to reconstruct the lake water balance in the past 2008 published by elsevier ltd

organic rich sediments in brine filled shaban and kebrit deeps northern red sea the element compositions si ca and al of up to 2 1 1 ka old sediments in about 10 in long cores from the southern basin of the shaban and kebrit deeps in the northern red sea allowed a classification of major sediment types in carbonate sands and muds and siliceous oozes a feooh enriched sediment horizon and a few samples with high zn values in the kebrit core indicate a hydrothermal origin probably near the brine sea water interface with subsequent transport of hydrothermal compounds into the deep sediments high organic carbon contents up to 8 4 are positively correlated with the ba concentrations which suggests that high bioproductivity and rapid deposition c 14 dating suggests a sedimentation rate near 70 cm ka led to the formation of sapropelic sediments between 11 8 and 13 6 ka younger dryas organic petrological observations showed that the sediment organic material largely consists of 20 gm sized roundish fecal pellets intimate mixtures of organic matter and inorganic constituents and bituminite terrestrial organic matter pollens of land plants fusinite etc is very rare in the sediment cores from both deeps organic geochemical investigations of kerogens and organic extracts show that a significant hydrothermal hydrocarbon production did not occur in near surface sediments of the shaban and kebrit deeps rock eval pyrolysis of kerogens characterised the organic matter to be of type ii quality the delta c 13 values of the kerogens from the most prominent sapropel in the shaban deep indicate an enrichment of c 12 rich nutrients in the water column during postglacial sapropel formation in the younger dryas the n alkane spectra are dominated by short chain lengths between n c 15 and n c 25 prevailing n c 15 to n c 25 alkanes in low mature sediments are indicative of algal and microbial source pristane phytane ratios are generally low i to similar to 1 which suggests that anoxic conditions prevailed within the anaerobic brine filled deeps for the whole time covered by the sediments this again indicates that sapropel formation was caused by high bioproductivity in the northern red sea rather than episodic stagnation with better preservation of the organic matter long chain alkenones and sterols are the dominating compounds of the lipid fraction cholesterol contents in the sediment cores reflect phases of eukaryotes production in the water column whereas the positive correlations of dinosterol with toc and the amounts of total extract suggests that the major organic carbon source in the northern red sea during postglacial high productivity stages were dinoflagellates another important carbon source however is indicated by the occurrence of 22 29 30 trisnorhopan 21 one tnh although the formation of tnh from its precursors is not fully understood this compound probably results from microbial degradation of intact bacteriohopanepolyols bhp which can be used as indicators for bacterial abundances and phyla tnh is most likely produced at the brine sea water interface where sedimenting organic matter accumulates and if the redoxcline corresponds to the density gradient the organic matter is subjected to efficient aerobic bacterial degradation processes however during high bioproductivity stage younger dryas the redoxcline was probably higher in the water column and thus a significant tnh production at the brine sea water interface did not occur at times of sapropel formation in the northern red sea deeps c 2007 elsevier b v all rights reserved

cenozoic evolution of the eastern danish north sea this paper provides a review of recent high resolution and conventional seismic investigations in the eastern danish north sea and describes their implications for the development of the eastern north sea basin the results comprise detailed time structure maps of four major unconformities in the eastern danish north sea the top chalk surface mid paleocene near top oligocene the mid miocene unconformity and base quaternary the maps show that the eastern danish north sea has been affected by faulting and salt diapirism throughout the cenozoic carbonate mounds erosional valleys and pockmark or karst like structures were identified at the top of the upper cretaceous danian chalk group strike parallel erosional features and depositional geometries observed at near top oligocene and at the mid miocene unconformity indicate that these major sequence boundaries can be attributed to large scale lateral changes in sediment supply directions increases in sediment flux to the southeastern north sea at the eocene oligocene transition and in the post middle miocene appear to correlate with similar events world wide and with long term 18o increases indicating forcing by global factors i e eustasy and climate stratal geometries observed on the seismic data indicate that the so called neogene uplift of the eastern danish north sea may have been hundreds of metres less than previously suggested it is argued that late cenozoic uplift of the basin margin and of mountain peaks in southern norway may have been caused entirely by isostatic uplift of the crust in response to accelerated late cenozoic denudation and dissection of topography created in the paleogene the late cenozoic periods of accelerated denudation and incision rates were most likely driven by climatic deterioration and long term eustatic lowering rather than active late cenozoic tectonics the cause of which is conjectural a series of shallow thrust structures and an associated system of deep buried valleys were mapped thrust faulting most likely occurred in response to gravitational loading at the margin of an advancing ice sheet and it was followed by deep incision due to subglacial melt water erosion probably during the elsterian glaciation