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30th International Meeting on Organic Geochemistry (IMOG 2021)
- Conference date: September 12-17, 2021
- Location: Online
- Published: 12 September 2021
151 - 200 of 279 results
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SOURCE ROCK CANDIDATES IN THE SOUTH OF WESTERN SIBERIA, RUSSIA
Authors V. Samoilenko, I. Goncharov, P. Trushkov, N. Oblasov, M. Veklich, S. Fadeeva, R. Kashapov and A. LitvinovaSummaryA complex of geochemical studies on core samples from the south of the Western Siberia Basin, Russia has been performed. Pyrolysis data from rock samples of Lower Cretaceous and Jurassic sediments establish the presence of at least four potential source rock intervals in the study area. The Upper Jurassic Bazhenov interval hosting marine organic matter has the greatest potential for oil and gas generation. The other identified source intervals are of lower quality and do not have a potential for generating significant amounts of liquid petroleum due to the terrestrial nature of the organic matter.
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WHAT RESPONDS FIRST TO CLIMATE CHANGE: LEAVE OR ALGAE DERIVED BIOMARKERS?
Authors C. Schubert and R. SergeSummaryTo follow climate change in sediment cores it is important to now how quick a biomarker reacts to climate change. Here we investigated a sediment core from Lake Van retrieved during an ICDP campaign in 2021. We compare compound specific hydrogen isotopes measurements on biomarkers, i.e. long-chain n-alkanes and alkenones to understand which biomarker reacts first to, in this case, the water cycle (precipitation, evaporation) in the Eastern Turkey area.
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NOVEL BIOMARKERS ORIGINATED FROM TAXODIOIDEAE IDENTIFIED IN THE LATE CRETACEOUS SEDIMENTS
Authors M. Goryl, B. Simoneit, M. Bucha, M. Rybicki and L. MarynowskiSummaryThe presence of monoterpenylabietenoids, novel biomarkers from Taxodioideae has been studied using gas chromatography-mass spectrometry. Thermal maturity of the organic matter (OM) was low - mean vitrinite reflectance range from 0.34 to 0.45% Rr.
Here, we report the occurrence of important natural products, 7α- and 7β-p-cymenylferruginol (21,7α and 21,7β-p-isopropyl-benzylferruginol), along with two novel minor additional isomers, namely 3α- and 3β-p-cymenylferruginol, and their diagenetic biomarker products like: 7α- and 7β-p-cymenyldehydroabietane, 9,10-p-cymenylretene, 9-p-cymenylsimonellite and other.
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A SINGLE ARCHAEON COUPLES HYDROCARBON DEGRADATION TO METHANOGENESIS
Authors Z. Zhuo, C. Zhang, P. Liu, L. Fu, R. Laso-Pérez, G. Wegener, M. Li and L. ChengSummaryMethanogenic hydrocarbon degradation is the dominant biodegradation process in crude oil, and so far was described for syntrophic associations of hydrocarbon-degrading bacteria and methanogenic archaea. Recent culture-independent studies suggest that the archaeon ‘Candidatus Methanoliparum’ performs both reactions, involving alkyl-coenzyme M reductases for the activation of alkanes and canonical methyl coenzyme M reductases for methane formation. Here, we cultured ‘Ca. Methanoliparum’. Metatranscriptomics and isotope labelling experiments confirm the suggested pathway for the degradation of hexadecane to methane in this archaeon. Mass spectrometry identified CoM- bound intermediates for the activation of long-chain n-alkanes, n-alkylcyclohexanes and n-alkylbenzenes, showing the wide substrate range of this archaeon. The wide distribution of the ’Ca. Methanoliparum in reservoirs indicates that this alkylotrophic methanogen may play a vital role in the frequently observed transformation of reservoir oil constituents into methane,
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Organic Geochemistry and Depositional Conditions of Carboniferous Source Rocks from Wulungu Area, Junggar Basin
More LessSummaryIn summary, the geochemistry characteristics of the source rocks of the Carboniferous source rocks in Wulungu area reveal its fair to very good gaseous hydrocarbon generation potential.
The terrigenous vegetation was the predominant sources of the OM in the Carboniferous period. Analyses of the molecule parameters indicates a suboxic lacustrine hypersaline environments in WC area and a relative fresh water environment in Shibei Sag.
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GEOCHEMICAL CHARACTERISTICS OF THE LOWER CRETACEOUS XIGUAYUAN FORMATION MUDROCKS IN THE LUANPING BASIN, NORTHERN CHAINA
More LessSummaryThick and organic-rich mudrocks occur in the lower Cretaceous Xiguayuan Formation of the Luanping Basin, Northern China. However, the studies concerning geochemical characteristics of the mudrocks were limited. Shale oil was first discovered in Well LT-1 in Cretaceous Formation of Luanping Basin, filling the gap in the discovery of Mesozoic hydrocarbon in the Yanshan Structural Belt. In this study, the core samples in Well LT-1 and several outcrop samples from stratigraphic sections were collected. A combined investigation of organic and inorganic geochemistry was carried out to study the geochemical characteristics and paleo-environment as well as the controlling factors for organic matter accumulation. The Rock-Eval and organic petrology results indicate that the mudrocks have good hydrocarbon generation potential. Additionally, the biomarkers and elements show that the mudrocks were formed in the anoxic lacustrine sedimentary environment with a stratified water column varying from brackish to high salinity. The paleoclimate was semiarid, the paleoproductivity was moderate and the sedimentary rate was fast. The main sources of organic matter are aquatic plankton, and terrestrial higher plant. Excellent preservation and moderate productivity are the major controlling factors for organic matter accumulation in the Xiguayuan Formation.
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OVERMATURE SHALE GAS GENERATION: IMPLICATIONS FROM PYROLYSIS OF NATURAL SHALES OF LATE-OIL MATURITY
More LessSummaryAlthough retained oil in shales may contribute variably to the gas potential at overmature stages, it is difficult to restore the accurate amount of retained oils in “real” shales because oil expulsion in geological conditions is affected by too many factors. Alternately, it may be wise to investigate the overmature shale gas generation based on shales of late-oil maturity that have experienced oil expulsion in geological history. Sealed gold tube pyrolysis experiments reveal that the accumulative gas yields of late-oil shales have a maximum gas yield of 220 cm3/g TOC when they evolve into equivalent vitrinite reflectance (EqVRo) of 3.6%. Given that the gas contents of overmature Lower Silurian Longamxi shales in China are usually less than 200 cm3/g TOC, it is suggested that the preservation of shale gas may be more important than shale gas generation during overmature stages. This is because the gas amount in the present gas shales can be readily generated during the overmature stage even if the late-oil maturity shale has a TOC value of 1%, a much smaller value than the cut-off TOC value of 2% for most overmature shales in South China.
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TRACKING CARBON METABOLISM IN NOVEL ANAEROBIC ALKANE-OXIDIZING ENRICHMENT CULTURES WITH ISOTOPE PATTERN MATCHING
Authors J.S. Lipp, F. Schubotz, K. Hinrichs and G. WegenerSummaryRecent studies suggest an unforeseen role of archaea in the anaerobic oxidation of non-methane alkanes using enzymes of the methanogenesis pathway and requiring partnerships with bacteria that have not yet been cultured. Stable isotope probing (SIP) approaches provide an important culture-independent tool to track activity and carbon assimilation of these microorganisms in situ. However, the established stable isotope probing of lipids requires labor-intense purification of individual molecules and chemical derivatization or cleavage reactions such as ether-cleavage or saponification to produce GC-irmMS-amenable derivatives. A recently developed promising technique is isotope pattern matching (IPM) which uses isotopomer patterns of intact lipids analyzed by HPLC-MS to determine uptake of stable isotopes. We have incubated methane- and other short chain alkane-oxidizing enrichment cultures from hydrothermal sites in the Guaymas Basin with 13C-labeled bicarbonate and 13C-labeled alkane substrates at 50°C and monitored label-uptake into the lipid pool using traditional SIP and IPM methods. This presentation will show data of diagnostic lipids, including intact polar archaeal and bacterial lipids and compare IPM with traditional SIP experiments of selected biomarkers with the goal to understand carbon substrate affinity of alkane-oxidizing enrichment cultures.
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LIPID PROFILE DETERMINATION AND COMPOUND SPECIFIC ISOTOPE ANALYSIS OF BEAKED WHALE BLUBBER
By T. PlintSummaryThe lipid biogeochemistry of stratified blubber profiles was used to investigate the diet and physiology of elusive deep-diving beaked whales stranded in Scottish waters. Full blubber profiles (skin, outer-, middle-, and inner-blubber) taken from two whales (True’s beaked whale and Sowerby’s beaked whale) were analyzed for compositional lipid distribution and compound specific stable carbon isotope (δ13C) composition.
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2-METHYLHOPANES AS UNIQUE CYANOBACTERIAL BIOMARKERS BEFORE 1.2 BILLION YEARS AGO
Authors Y. Hoshino, B. Nettersheim, C. Hallmann, G. Vinnichenko, J. Brocks and E. GaucherSummaryThe bioavailability of molecular oxygen is considered a driving force for the evolution of phenotypic complexity, yet the geological history of biological oxygen production remains poorly constrained. Fossilized 2-methylhopanoids (2-methylhopanes) were once considered diagnostic for the presence of cyanobacteria and oxygenic photosynthesis. However, the subsequent discovery of C-2 hopanoid methyltransferase (hpnP) in non-cyanobacterial species questioned the utility of 2-methylhopanes as cyanobacterial biomarkers. Here we re-examined the distribution of HpnP in the bacterial domain and the evolutionary history of HpnP. Our results suggest that HpnP did not originate within α-proteobacteria but rather was already present in the common ancestor of cyanobacteria, contrary to previous inferences. Molecular clock analyses further suggest that the emergence of HpnP in cyanobacteria substantially predates the emergence of HpnP in α-proteobacteria and 2-methylhopanes in rocks deposited prior to 1.2 Ga are inferred to be derived uniquely from cyanobacteria. Our results imply that 2-methylhopanes can theoretically allow us to trace the rise of oxygenic photosynthesis even prior to the GOE if suitable sedimentary sequences or preservation windows should be found in the future.
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EXCEPTIONAL PRESERVATION OF LIPID BIOMARKERS IN A CRETACEOUS SERPENTINITE-HOSTED SUBSEAFLOOR HYDROTHERMAL SYSTEM
Authors F. Schubotz, L. Meyer, W. Orsi and F. KleinSummaryHere, we describe a high-resolution biomarker record of a fossil serpentinite-hosted hydrothermal system from the Cretaceous showing exceptional good preservation of core and intact polar lipid biomarkers along the steep geochemical gradients of a paleo subseafloor fluid mixing zone analogous to the present-day Lost City hydrothermal vent system. We observed remarkable changes in both bacterial and archaeal biomarker lipid composition following the geochemical transition from a reducing to an oxidizing environment. These studies have important implications for the search of life elsewhere in the universe.
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MOLECULAR BIOMARKERS IN COPROLITES ILLUMINATE DIETARY INTERACTIONS IN THE CARBONIFEROUS MAZON CREEK ECOSYSTEM
Authors M. Tripp, J. Wiemann, J.M. Hope, J.J. Brocks, P. Mayer, S. Lidgard and K. GriceSummaryCarbonate concretions are formed under unique conditions which result in exceptional preservation of organic matter through geological time. Coprolite fossils (diagenetically mineralised faeces) preserved in Mazon Creek Carboniferous (306 Ma) concretions have been analysed here using a biomarker approach for the first time, combined with carbon isotopes and multivariate statistical analysis of in-situ Raman spectroscopy data, providing insight into the diet of the producer species in the days before faecal deposition. The C27 steranes in the fossil portions of each concretion comprise greater than 95% of the total steranes, while the matrix portions have a lower overall abundance of steranes, demonstrating that the sterane distribution of the fossils represents the diet of the coprolite producer. Therefore, it is interpreted that the diet of the producer consisted of primarily animal material, suggesting a carnivorous diet, although an omnivorous diet also cannot be ruled out. Biomarkers combined with carbon isotopes here show the potential to distinguish carnivores and omnivores from herbivores in Carboniferous coprolites.
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Environmental Mechanisms Governing Formation of the Lower Silurian Organic Matter-Rich Mudstones in Baltic Basin (Lithuania)
Authors A. Cichon-Pupienis, R. Littke, J. Lazauskienė, A. Baniasad, L. Šiliauskas, D. Pupienis and S. RadzevičiusSummaryThe object of this research was the lower Silurian (Llandovery, Wenlock) succession in the Baltic Basin. The aim of this study was to assess the origin, type and thermal maturity of organic matter, distribution of litho- and organic facies, to reconstruct bottom-water redox conditions and to reveal the major regional and global mechanisms that had control on paleoenvironments and organic matter abundance in these shaly sediments. In order to reach the goal several methods were applied, e.g. sedimentological and petrographic studies, pyrite framboids measurements, organic and inorganic geochemistry, organic petrology, analysis of stable nitrogen and organic carbon isotopes. The study revealed that three sections: Aeronian, Telychian and Sheinwoodian-Homerian reflect different paleoenvironmental depositional conditions.
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An Integrated Biogeochemical and Geodynamic Model for a Riverine Originated Shallow Lacustrine Basin (Western Turkey)
More LessSummaryA limited number of inland lakes, formed during the earlier stages of the Holocene, are still present in near coastal areas of Eastern parts of the Aegean Sea. The coastal morphology and particularly the formation of these shallow lacustrine basins are predominantly controlled by the host-graben structures, such as Gediz, Kucuk and Buyuk Menderes in Central-Western Anatolia ( Hakyemez et al., 1999 ). This study represents an integrated geodynamic and biogeochemical approach, with a great potential for paleo-environmental reconstructions of such riverine originated shallow lakes.
As a pilot monitoring site, we focused on Lake Marmara basin, which developed in a residual-branch on the northern sector of Gediz Graben and paleo-Gediz valley. During the drilling campaign in 2003, the maximum water depth was 4.5m in the western depositional centre of the lake (WD) and even lower (4m) in the eastern depo-centre (ED). These two sub-basins are currently separated by a north-south striking ridge, as evidenced by reduced water level and geophysical (ground penetrating radar) data. Two cores one from each depositional centre, of 140cm (H3:WD) and 145cm (H5:ED) length, respectively, were retrieved from the lake. The entire sediment archive of these cores covers the last 10ka span environmental history of the basin.
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NEW INSIGHTS INTO THE RISE OF EUKARYOTES FROM LIPID BIOMARKER RECORDS FROM TONIAN-EDIACARAN CORES FROM SIBERIA
Authors A. Rizzo, A. Bekker, V. Ershova and G. LoveSummaryEmerging consensus suggests that the late Tonian period (∼820-720 Ma) was an interval of dynamic Earth system change. Regular (4-desmethyl) steranes have not been robustly detected in rocks older than ∼820 Ma, suggesting that eukaryotes were not significant as primary producers in the marine environment until then. Despite growing interest in the Tonian Period, biomarker stratigraphic records are still relatively sparse. Here we present new free and kerogen-bound biomarker data from well-preserved rocks from the Lena-Anabar basin, Siberan craton, Russia. Two drill cores, sampled about 100 km apart, give stratigraphic coverage that spans the late Tonian (∼800-720 Ma) and Ediacaran period and allow insights into spatial heterogeneity in environmental conditions. Lipid biomarkers obtained from solvent extraction were analyzed using full scan and multiple reaction monitoring (MRM)-GC-MS. Kerogen-bound biomarkers were liberated using the catalytic hydropyrolysis (HyPy) technique, allowing us to verify a biomarker signal that is syngenetic to the host rock. Biomarker distributions found across the Tonian-Ediacaran transition record fluctuating ecological and environmental conditions across the basin during an interval of dynamic change in the global biosphere.
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MOLECULAR CHARACTERIZATION, FATE AND ANTIOXIDANT CAPACITY OF SPHAGNUM PHENOLS AND THEIR EFFECT ON PEATLAND CARBON CYCLING
Authors C. Murty, A. Charlton, N. Gray, C. Vane and G. AbbottSummaryPhenolic compounds play a crucial role in northern peatland dynamics by inhibiting the degradation of organic matter in surficial peat layers. There is uncertainty as to how the phenolic content of both Sphagnum moss and northern peats will respond to intensified drought events, which are increasing in occurrence. This research aims to disentangle the fate of ‘free’ phenolics in peatlands by identifying and tracking a series of targeted, water-soluble phenolic acids, and determining their antioxidant capacity (following their release into peat DOM from peat/moss). The source, stability and fate of these compounds and the extent at which they contribute to the antioxidant pool in northern peats remains unknown.
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Implications of Meor and Waterflooding for Geochemical Interpretation of Recovered Oils Based On Esi(-) Ft-Icr Ms Analyses
Authors L. Gicovate Paes Sodré, L. Martins, G. Feitosa, B. Vaz and D. FrancoSummaryThe oil of difficult recovery that remains in the reservoir has high acidity and is rich in polar compounds of high molecular weight. Reports about recovered oil compositional analyses are not common, due to analytical limitations. However, this was overcome with the emerging mass spectrometry technique with high resolving power (FT-ICR MS), especially when coupled to electrospray ionization source in negative mode [ESI (-)] to assess acidic polar species. Here, we evaluated the effect of brine (Waterflooding) and biosurfactant (MEOR) injections in acidic polar compounds of the recovered oils, after oil displacement test carried out in a porous medium. The results showed that there is a general trend of changes in polar acid composition, affecting the geochemical interpretation. Regarding the maturity assessment by N class, the recovered oils are subtle affected due to a greater relative abundance of carbazoles (DBE 9). Additionally, biodegradation ratios based on the O class are affected, showing an increase in the relative abundance of low DBE compounds for recovered oils. Other biodegradation ratios calculated for the O2 class are also affected (e.g., A/C ratio), in which the recovered oils are misleading classified as non-biodegraded, whereas Control Oil is classified as light to moderately biodegraded.
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Estimating shale gas resources in the Lower Carboniferous mudstones of northern England
Authors M. Sims, A. Fraser, J. Watson, M. Sephton and C. VaneSummaryThe Carboniferous mudstones of northern England have been considered as a potential source rock for development of shale gas resources. The viability of the source rock is in part dependent on its potential to generate hydrocarbons. New geochemical data from boreholes across northern England is presented, and the original organic parameters are predicted for mudstones of different ages. The findings concur with other assessments of the mudstones, that they contain a considerable detrital and inert component which could be detrimental to the development of the resources. New original organic content parameters for the source rock are recommended for future petroleum systems modelling and resource interpretation.
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DISTRIBUTION OF BACTERIOHOPANEPOLYOLS IN THE GULF OF MEXICO WATER COLUMN AFTER A DEEPWATER OIL SPILL
Authors I. Hölscher, N. Richter, F. Mienis, E.C. Hopmans, J.S. Sinninghe Damsté, S. Schouten and D. RushSummaryMethane (CH₄) is a potent greenhouse gas, and changes in its biogeochemical cycle can influence the global climate system. Extreme shifts in atmospheric and marine CH₄ emissions have happened in the past. In marine environments, aerobic methane oxidation (AMO) is the last CH₄ sink before it reaches the atmosphere, and thus plays an important role in regulating marine CH4 emissions.
The Deepwater Horizon blowout in April 2010 caused the largest marine oil spill in history (∼4.4 x 10⁶ ± 20% barrels of oil). The oil and gas that was discharged into the water column stimulated the growth of multiple methanotrophs and other hydrocarbon utilizing bacteria. Bacteria performing AMO synthesize specific bacteriohopanepolyols (BHPs) that are used as lipid biomarkers for AMO. To investigate possible community shifts induced by an extreme gas emission event we collected sinking particulate matter before and after the blowout to identify BHPs of the local bacterial community performing AMO. Our study aims to elucidate the interplay between extreme methane emissions into the ocean and aerobic methanotrophy in the water column. Moreover, the results of this study will be used to interpret past BHP distribution and abundances in sediment records in the Gulf of Mexico.
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An Optimized Analytical Method to Quantify Pyrogenic Carbon Using Benzene Polycarboxylic Acids in Marine and Lacustrine Samples
Authors N. Penalva Arias, J. Villanueva, G. Muñoa, C. Laguna, P. Rivas, M. Raja and A. Rosell-MeléSummaryBenzene polycarboxylic acids (BPCAs) have been used as molecular markers to quantify and characterize pyrogenic carbon (PyC) in complex samples. The existing analytical procedures to generate and quantify BPCAs are time-consuming and cannot be used to analyse a large number of samples. Here, we present an optimized methodology to quantify BPCAs in marine and lacustrine samples. It involves a multi-step procedure that includes the oxidation of the aromatic structures of the PyC to generate the BPCAs using a microwave-assisted acid digestion, reducing oxidation time 4 times over the conventional methodology. Interfering cations (Fe) were removed with a cation exchange resin using 40% methanol as a solvent elution. The sensitivity and selectivity of the analysis was greatly improved by using HILIC chromatography coupled to tandem mass spectrometry using an electrospray interface. The sensibility and reproducibility of this method was evaluated using the method of standard addition of individual BPCAs compounds in marine samples. In addition, we have appraised our methodological approach and the use of BPCAs as proxies of wildfire occurrence and magnitude using set surface sediments from Spanish lakes and wildfire database spanning 5 decades.
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A NORMALIZED THERMAL MATURATION PATH FOR CALCULATING TRANFORMATION OF MARINE KEROGENS
Authors Y.O. Rosenberg and I.J. ReznikSummaryEvaluation of kerogen transformation with thermal maturation is often assessed with open pyrolysis Rock-Eval apparatus. The decrease in hydrogen index (HI, mgHC/gTOC) with the increase in Tmax of kerogens can be viewed as a maturation path, which describes the process of kerogen transformation into hydrocarbons. Despite the importance of sulfur-rich marine kerogens (Type II-S) in supporting petroleum systems worldwide, only the maturation paths of Types I, II, and III kerogens have been described by Rock-Eval parameters. Considering the role od S on thermal maturation, a new normalized maturation path for marine kerogen is formulated using induced maturation data, and confirmed using natural maturation data. The normalized maturation path minimizes the inherent heterogeneity of the different kerogens and instrumental variability that can affect the measured Rock-Eval parameters. Hence, the normalized scale is offered as a tool to better evaluate the transformation ratio of marine kerogens directly and continuously along the maturation path.
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SIGNIFICANCE OF ACIDIC POLAR SPECIES ASSESSED BY FT-ICR MS TO REVEAL GEOCHEMICAL INFORMATION OF OILS FROM THE SERGIPE-ALAGOAS BASIN
SummaryIn this work, we investigate in detail the acidic polar composition of five oil samples from distinct fields of the Sergipe-Alagoas Basin (Brazil) by FT-ICR MS using ESI(-). We aim to present the significance of acidic species to reveal geochemical information of petroleum fluids and to reconstruct the maturity and depositional environment of the source rocks by extracting features of biodegradation. The heteroatom class distribution of the oil samples shows great variability, with a higher abundance of N and O2 classes, followed by the O1, NO, and NO2 classes. The biodegradation was successfully assessed by the A/C ratio and SA index based on the O2 compounds, classifying the samples in four levels of biodegradation (from non to heavy biodegraded). The maturation was assessed by the distribution of the N compounds, showing that samples have reached the peak of the oil window, but the heavy biodegraded oil was misleading evaluated with higher maturity. The depositional environment was evaluated using the C27/C28 (DBE 4) ratio and the suggested Isoprenoidyl phenol index, differentiating the lacustrine oil samples from the marine evaporitic ones. However, care should be taken in the assessment of highly biodegraded oils since the acidic compounds are considerably affected.
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LATE HOLOCENE MONGOLIAN CLIMATE RECONSTRUCTIONS FROM LOCALLY CALIBRATED GDGT AND POLLEN TRANSFER FUNCTIONS FOR LAKE AYRAG.
SummaryThe 4,000 year cal. BP pollen and brGDGT sequence from Lake Ayrag documents the Mongolian Late Holocene climate and human impact variations.
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PUSHING THE LIMITS OF DETECTION: INVESTIGATING THE STRUCTURE OF 2.4 GA OVERMATURE KEROGEN
More LessSummaryThe study of kerogen can aid in understanding the evolution of life on Earth by yielding geochemical information on ancient organisms. However, the study of kerogen in Precambrian overmature rocks is problematic due to uncertainty regarding biogenicity. Ancient kerogens are commonly simplified, having lost most of their structural information during catagenesis and metagenesis. Therefore, careful study of candidate Precambrian-age kerogen is required to find primary structural information.
Here we examine organic matter in a well-preserved (metamorphic temperature ∼230°C) dolomite microbialite reef complex of the ∼2.4 Ga Turee Creek Group, Western Australia. This group contains diverse stromatolites, thrombolites, and shallow and deep-water microfossil assemblages preserved in black chert, and enigmatic branched organic structures (Fig. 1; Barlow and Van Kranendonk, 2016; Barlow et al., 2018).
Total organic carbon values are low (0.02–0.5 wt%), but kerogen bands in Raman spectroscopy are abundant, and consistent with regional thermal maturity estimates. In addition, FTIR and micro-FTIR studies showed significant chemical differences between the fossil organisms. The different characteristics support biogenicity of the kerogen and derivation from different living sources. This work demonstrates that information gained from in situ measurements of Precambrian overmature kerogen retains more information than from analysis of homogenised overmature kerogens.
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Mobilization of Ancient Carbon from Thawing Permafrost to Laptev Sea (Arctic Ocean) Sediments During the Last Deglaciation
Authors A. Nicolas, J. Hefter, R. Stein and G. MollenhauerSummaryThe aim of this study is to provide evidence of the mobilization of ancient carbon from thawing permafrost to the Laptev Sea sediments during the last deglaciation. The Lena is one of the largest Siberian Rivers that drain extensive permafrost areas into the Laptev Sea. In this study, we use a marine sediment core from off the Lena River outflow located on the Laptev Sea continental slope to reconstruct deglacial permafrost thaw events by analyzing terrigenous biomarkers (high-molecular weight n-alkanoic acids (fatty acids); branched glycerol dialkyl glycerol tetraethers (brGDGTs)) and carbon isotopes (Δ14C and 𝛿13C). The sediment core covers the period between ∼16,500 and 9,300 cal years BP and therefore covers most of the deglaciation. By combining the records of mass accumulation rates at the core location and age at deposition of terrigenous biomarkers extracted from sediment samples, we can determine the occurrence of past massive permafrost degradation and mobilization. The results from this study will further contribute to and extend the limited data sets on the age of deglacial permafrost carbon from the Laptev Sea and provide additional insights on the fate of permafrost-derived soil organic carbon in a warming climate.
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A POSSIBLE RAPID EUKARYOTE REVIVAL FOLLOWING THE LATE PERMIAN MASS EXTINCTION
Authors Y. Huang, B.D.A. Naafs, R.D. Pancost, L. Tian, D.P.G. Bond, P.B. Wignall and M.J. BentonSummaryThe Late Permian mass extinction is the largest mass extinction of whole geological history, followed by a prolonged life recovery expending the early Triassic. To better understand the recovery pattern of primary productivity through Permo-Triassic intervals and its longer-term changes in early Triassic, we applied biomarkers to reveal the community evolutions of marine primary producers. Our results indicate a possible rapid recovery of eukaryotic primary producers after the extinction during Griesbachian-Dienerian.
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Variations in Pigments, Fatty Acids and Sterols in Arctic Barents Sea Surface Sediments Across Contrasting Sea Ice Extent
Authors M. Stevenson, R. Airs and G. AbbottSummaryIncreases in Arctic sea ice extent have been observed over the past decades with warming at the high latitudes especially pronounced, including in the northern Barents Sea. To track variability between years in the timing and extent of ice-out we compared surface sediment pigment, fatty acid and sterol compositions between ice abundant (2017 and 2019) and ice-free (2018) summer sampling seasons across a south to north 30° E gradient. We found total chlorophyll-derived pigments varied predictably across the transect, and were usually markedly higher at station closest to the Polar Front transition. In 2018 which had an unusually low ice-extent and an early ice-out in the northern Barents Sea confirmed by satellite imagery, highest concentrations were present in the northerly station, indicative of increased production from phytoplankton. This trend was mirrored by total fatty acid methyl esters (FAMEs) which in 2018 showed progressive increases from southern to northern stations, with the pattern driven predominantly by short-chain FAMEs which are abundant in phytoplankton. Our findings have consequences for the functioning of the Arctic carbon cycle – if retreat of Arctic sea ice persists and ‘atlantification’ continues, then delivery of phytoplankton bloom-derived carbon to the seafloor could intensify.
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Impact of the Deep Subseafloor Microbiome on Sedimentary Biomarker Records in the Chicxulub Impact Crater
More LessSummaryActive and metabolically diverse microbial communities are living in the deep subsurface biosphere but little is known about their role in potential alteration of individual sedimentary lipid biomarkers. Here we performed a highly-resolved paired biomarker and microbial community statistical analysis on Early Eocene subseafloor sediments in the Chicxulub Impact Crater (Yucatán, Mexico). A subset of the bacterial communities showed significant correlations with the biomarkers identified. Polycyclic aromatic hydrocarbons (PAHs) were the most susceptible components to microbial degradation, while isorenieratane, hopanes, n-alkanes and steranes were less prone to microbial attack due to early abiotic diagenetic sulfurization. Microbial degradation likely also influenced the gammacerane index but not the pristane/phytane ratio. A subset of these putative hydrocarbon degraders was nitrate-reducers inferred from predicted gene function analysis. Overall, this study showed that non-sulfurized biomarkers in ancient sediments may still undergo in situ biodegradation in deep subsurface environment, limiting their use as reliable proxies for paleoenvironment reconstructions.
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SULFUR-BOUND BIOMARKERS RECORDED CLIMATE AND ENVIRONMENTAL CHANGES ALONG THE END PERMIAN MASS EXTENSION EVENT
Authors L. Shawar and R. SummonsSummaryIn this study we are investigating sulfur-bound biomarkers in the Meishan section that believed to be the best section that holds the Global Boundary Stratotype Section and Point (GSSP) marking the Permian-Triassic mass extinction. Sulfur-bound hydrocarbons in the Meishan section were never studied before. This in turn might affect the paleo-environmental interpretations in significant ways. Preliminary results shows that many biomarkers are exist in the sulfur-bound fraction extracted from the Meishan outcrops.
In this talk we are going to present different biomarker trends (including sulfur-bound ones), and their climate and paleo-environmental interpretations regarding the biota crises in the Phanerozoic.
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The Biomarker Distributions of Light Oils and Condensates in the Xihu Depression, East China Sea Basin
More LessSummaryThe Xihu Depression in the East China Sea Basin is a petroliferous depression. Recently, many breakthroughs continuously have been made it one of the most promising regions for petroleum exploration in the East China Sea. However, the origin of the petroleum in the Xihu Depression still remains controversial and is not well understood. In order to investigate the thermal maturity, depositional environment, and source materials of light oils and condensates, gas chromatography-mass spectrometry analyses of the saturated fractions were performed.
The distribution of n-alkanes, C29 sterane isomerization ratio and C31 22S/(22S+22R) homohopane ratio indicates that the light oils and condensates were generated within the early to early peak oil window. The dominance of C29 regular steranes and the almost complete absence of C27 regular steranes, the abundant diterpanes and the presence of oleanane suggest a dominant contribution from terrigenous source materials. The high Pr/Ph ratios, dominance of C29 steranes, distribution of hopanes, near-absence of gammacerane indicate that the source rocks for the hydrocarbons were deposited in a relatively oxic environment.
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TRACKING THE EVOLUTION OF THE SILURIAN MARINE BIOSPHERE USING LIPID BIOMARKERS AND STABLE ISOTOPE GEOCHEMISTRY
Authors N. Marshall, G. Love, A. Bekker and V. GrytsenkoSummaryThe Silurian Period was an important transitional interval in the evolution of life in both the terrestrial and marine realms, yet detailed Silurian lipid biomarker records are surprisingly scarce. We have analyzed the lipid biomarkers from a well-preserved 400m drill core from Podolia (Baltica) that covers the breadth of Silurian time to investigate the changing ecology and ocean chemistry that prevailed on a palaeotropical shallow marine shelf through the Silurian-Devonian transition. Using Multiple Reaction Monitoring (MRM)-GC-MS analysis we have compiled a detailed lipid biomarker stratigraphy tracking the environmental conditions and marine communities that occurred in Silurian shallow reef ecosystems and in more distal marine settings. Paleoenvironmental conditions favored bacteria over algae in these nutrient-depleted marine habitats. Some notable biomarker characteristics (high hopane/sterane, C29 sterane dominance, and high 3β-methylhopanes abundances) are similar to those previously found for Ordovician marine rocks, but the Silurian distributions are distinct from Late Devonian biomarker assemblages. The 3-MeHI values usually associated with appreciable contributions from microaerophilic methanotrophic bacteria show a gradual temporal decrease in magnitude when moving into the Early Devonian. This systematic change could reflect an increasingly muted marine and sedimentary methane cycle influenced by a rising inventory of dissolved oxidants and progressive ocean oxygenation.
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Uncommon Glycerol Monoalkyl Glycerol Tetraethers (GMGT) Support Membrane Adaption in the Archaeon Pyrococcus Furiosus
Authors M. Tourte, P. Schaeffer, V. Grossi and P. OgerSummaryMicrobes preserve membrane functionality under fluctuating environmental conditions by modulating their membrane lipid composition, a strategy termed homeoviscous adaptation. Although several studies have documented this strategy in Archaea, the influence of the majority of biotic and abiotic factors on archaeal lipid compositions remains unexplored. To constrain the homeoviscous adaptation strategies in Archaea, we studied the influence of temperature, pH, salinity, elemental sulfur, carbon source, and genetic background on the remarkable core lipid composition of the hyperthermophilic and neutrophilic marine archaeon Pyrococcus furiosus. Most growth parameters tested here affected its core lipid composition, the carbon source and the genetic background having the greatest influences. Surprisingly, P. furiosus membrane adaptation appears to marginally rely on the two major homeoviscous responses implemented by Archaea, i.e., the regulation of the ratio between diethers and tetraethers and of the number of cyclopentane-rings in tetraethers. Instead, it increases the ratio of monoalkyl (GMGT) over dialkyl (GDGT) tetrathers in response to decreasing temperature and pH and increasing salinity. Besides P. furiosus, numerous other species synthesize significant proportions of GMGT, which indicates that this unprecedented homeoviscous strategy might be common in Archaea. This paves the way for developing novel, GMGT-based environmental proxies.
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Comparison of Very Low Sulphur Fuel Oil With Spilled Oil Following Grounding of Mv Wakashio in Mauritius, 2020
More LessSummaryThe bulk carrier MV Wakashio ran aground on a coral reef offshore of Pointe d’Esny, Southeast Mauritius releasing an estimated 1000 t of fuel oil into the Indian Ocean threatening internationally important wetlands. It was reported to be carrying approximately 3,800 t of Very Low Sulphur Fuel Oil (VLSFO, defined as <0.5 %). A sample of oil was collected from close to shore and subsequently shipped to laboratories of (WA-OIGC), Perth, Australia and Woods Hole Oceanographic Institution (WHOI), USA for analysis. Together with a sample of Wakashio fuel oil, multi-spectroscopic techniques, including high resolution gas chromatography mass spectrometry, compound specific isotopic analysis and elemental analysis, were used to characterise and compare the oils.
Initial results were consistent with the spilled oil being a type of VLSFO. Although somewhat weathered, key biomarker profiles of the spilled oil matched the Wakashio fuel oil. This is to our knowledge the first reported spill of VLSFO.
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Sponges, Symbionts or Side-Chain Scrambling: What are the Major Sources of Neoproterozoic C30 Steranes?
Authors G. Love, A. Zumberge and P. CárdenasSummaryThree C30 sterane compounds are typically found together in the Cryogenian and Ediacaran rock record. This represents only a small subset of all structural possibilities from altering the side-chain chemistry. Both 24-isopropylcholestane (24-ipc) and 26-methylstigmastane (26-mes) are produced in abundance by some groups of demosponges and have been used as early animal biomarkers. Recently, it has been suggested that these C30 steranes are principally derived from diagenetic modification of C29 sterol precursors made by ancient green algae. If correct, this undermines their robustness and the interpretative value of these steranes as early animal markers. To assess which mechanism (biogenic vs. side-chain alteration) can account for the patterns of C30 steranes found in the Neoproterozoic rock record, we need to know the range of steroid structures that can be made in abundance by modern sponges. The sterols in over fifty sponge species were analyzed to identify those groups that make C30 and higher sterols. Catalytic hydyropyrolysis (HyPy) of sponges was conducted to convert sterols into steranes to elucidate the sterane elution patterns and six resolvable C30 steranes have already been detected. We will discuss the implications of these new sponge steroid findings for understanding the origins of Neoproterozoic C30 steranes.
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POST IMPACT RECOVERY OF THE DEEP GRANITIC BIOSPHERE OF THE CHICXULUB IMPACT CRATER
Authors S.N. Quraish, K. Grice, C. Cockell, A. Holman, P. Hopper, D. Kring, M.E. Bottcher and M. CoolenSummaryThe Chicxulub crater (Yucatan Peninsula, Mexico) is the third-largest, but the only well preserved large meteorite impact structure on earth. The 180 km-wide Chicxulub crater was created ∼66.5 Ma ago upon impact by the 14 km diameter asteroid that caused the Cretaceous–Paleogene (K–Pg) mass extinction involving all non-avian dinosaurs as well as 75% of all terrestrial and aquatic species. The previous studies are limited to fossilizing species, but recent studies have reported the post-impact recovery and return of surface-dwelling microbial life to the Chicxulub impact crater site. However, to what extent the deep biosphere was able to recover from the impact required further investigation. In 2016, an 829.03-meters-long core between 505.7 to 1334.73 meters below the seafloor (mbsf) within the craters’ peak ring was recovered as part of the International Ocean Discovery Program (IODP) Expedition 364. We studied the diversity and distribution of microbial community present in the granitic basement and associated mineral veins (774.41–1334.73 mbsf) of the recovered core through environmental 16S rRNA sequencing. The preliminary results show that deep biosphere comprises a highly diverse community of putative thermophilic heterotrophic, sulfate-reducing, and Mn-oxidizing bacteria as well as putative hydrogenotrophic cyanobacteria.
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ENHANCED METHANE CYCLING IN THE EARLY PALEOZOIC OCEAN
Authors M. Rohrssen, G. Love, C. Lee, N. Marshall, A. Kuhl and R. PancostSummaryMicrobial production and consumption of methane represent critical components of Earth’s carbon cycle and climate system. Methane cycling feedbacks on climate may have been important during the Paleozoic Era, with anoxic deep waters and low sulphate promoting greater fermentative recycling of sedimentary organic matter and an enhanced methane cycle. We find that the typical Phanerozoic marine average for the 3-methylhopane index of 1–3% is substantially and consistently exceeded in a large suite of Ordovician and Silurian marine rocks from Laurentia and Baltica, often by an order of magnitude. Although other bacterial sources are possible for 3-methylhopanoids (3-MeH), in many Paleozoic marine rocks and oils these were largely derived from microaerophilic methanotrophic bacteria. Strong support for this methanotrophic bacterial source assignment comes from compound-specific δ13C analysis on individual hopane compounds. The Ordovician and Silurian hopanes yield some of the most 13C-depleted signatures found for Phanerozoic marine hopanes, outside of unusual methane seep settings. The protracted decrease in 3-MeH abundance through the Silurian-Devonian transition may be tracking the progressive oxygenation of the deep global ocean. Here, we test this idea by expanding the existing organic geochemical dataset on Ordovician and Silurian rocks with biogeochemical modeling of the Ordovician Earth system.
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Holocene Paleoenvironmental and Paleoclimatic Changes in North Cameroon: The Ngaoundaba Peat Record
Authors V. Schaaff, M. Makou, V. Grossi, S. Ansanay-Alex, I. Antheaume, P. Deschamps, B. Hamelin, Y. Garcin, D. Sebag, B. Ngounou Ngatcha and G. MénotSummaryIn this study, we investigate a 6-meter peat core from the NGaoundaba peatland (Northeastern Cameroon) covering almost 10 ka using bulk geochemical data and a large panel of biomarkers [Isoprenoid and branched glycerol-dialkyl-glycerol-tetraethers (isoGDGT and brGDGT respectively), n-alkanes, hopanoids and degradation products of plants]. Recent peat-specific temperature and pH calibrations based on brGDGTs ( Naafs et al., 2017 ) were applied to the NGaoundaba peatland stratigraphic record. GDGT-based temperature and pH are coherent with insolation variation ( Berger, 1981 ) and with pollen-based records from Lake MBalang ( Vincens et al., 2010 ), situated 20 km to the north of NGaoundaba. The recent peat-specific hopane-based pH calibration ( Inglis et al., 2018 ) was applied to the NGaoundaba record. Hopane and GDGT-based pH estimates present strikingly similar variations, raising new perspectives about potential brGDGT origins.
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Organic matter source input, paleodepositional conditions and source rock potential of the Mid-Permian Wandrawandian siltstone, Southern Sydney Basin, Australia
Authors N. Pasadakis, P. Tserolas, N. Bayer, E. Chamilaki, A. Zellilidis and A. MaravelisSummaryThis study examines the organic matter source input, paleodepositional conditions and source rock potential of the Mid Permian Wandrawandian siltstone in the Southern Sydney Basin, Australia. The obtained data provide indications of a generally poor, gas-prone source rock potential, with TOC% values averaging close to ∼1% but generally low S2 values, barring some samples with a fair potential worth considering further investigation. The organic matter is thermally mature and having experienced high temperatures during burial.
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BIOMARKER DISTRIBUTION THROUGHOUT THE MESOPROTEROZOIC NONESUCH FORMATION, USA
Authors L. Van Maldegem, P. Strother and J. BrocksSummaryThe oldest eukaryotic microfossils have been found in late Paleoproterozoic sediments (∼1.69 Ga), yet the oldest molecular fossils are detected in units younger than 0.8 Ga. Yet the majority of sedimentary deposits either preserves microfossils or lipids, making it challenging to identify the eukaryotic lipid signature in the mid-Proterozoic. Recently, a large variety of eukaryotic microfossils in specific palynomorph rich horizons of the 1.1 Ga Nonesuch Fm were identified. Here we investigated the indigenous lipid biomarkers of the Nonesuch Fm. We observed indigenous lipid signatures, which display a similar bacterial dominated biomarker distribution as seen in other Proterozoic sedimentary sequences.
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The Distribution of Structurally Diverse Adenosyl Bacterio-Hopanepolyols in Soils: Insight into Envrionmental Adaptations
Authors D. Rush, K. O’Connor, N. Smit, M. Berke, L. Villanueva, J. Sinninghe Damsté and E. HopmansSummaryAdenosyl bacteriohopanepolyols (BHPs) are used in proxies to assess the input of terrestrial organic matter into marine systems. More recently, evidence has indicated that some adenosyl BHPs may also be produced in situ in marine oxygen deficient zones by chemotrophic bacteria, casting doubt on their use as a proxy for soil input into marine settings. Furthermore, although adenosyl BHPs with three different headgroups have been described, only one (adenosyl BHP) has been fully structurally elucidated.
Here, we use reversed phase UHPLC coupled to Electrospray Ionization/Tandem High Resolution Mass Spectrometry (ESI/HRMS2) to analyse and identify an unprecedented structural diversity in environmental BHPs. We used the exact mass of fragment ions to determine elemental compositions and, for the first time, tentatively assign structures to 14 BHPs contained adenosyl-type head groups. Our initial results suggest that adenosyl BHPs might be a complementary proxy to other proxies such as MBT/CBT for pH, mean annual air temperature and mean annual precipitation in low temperature environments. It is anticipated that our on-going combined lipidomic and metagenomic work will cast light for the first time on potential genetic variations responsible for this diversity.
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Fate of Plastics and Their Additives in Alkaline Solution at Different Temperatures
Authors H. Ben Zeineb, C. Le Milbeau, P. Blanc, P. Ollivier, L. Andre and M. BoussafirSummaryStorage in a deep geological layer is the final destination for radioactive waste (ILW). In these conditions, the organic waste can be in contact with the infiltrated water and can release new hydrophilic oragnic products, which can complex and remobilize radionuclides. In this work, we are looking for investigate the release of organic ligand from plastics (PVC and PE) at 2 temperatures.
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Single Step Extraction and Clean up Method for the Multiproxy Analysis of Biomarkers in Sediments and Aerosols
Authors M. Raja, C. Moreu, C. Laguna, N. Penalva, J. Villanueva and A. Rosell-MeléSummaryOrganic biomarkers have proven their value as tools, among others, to reconstruct past environmental conditions, understand human impacts in the environment, and trace the transport pathways of the carbon cycle in sedimentary basins. For this reason, a wide variety of biomarkers (e.g. n-alkanes, C37 alkenones, GDGTs, polyaromatic hydrocarbons, n-alcohols and sterols) are routinely investigated and applied in the environmental and Earth sciences. However, current methodologies for the simultaneous analysis of an ensemble of compounds are labour intensive and time-consuming, which hamper the analysis of a large number of samples quickly and reliably.
Here, we present a modified analytical approach from standard techniques to quantify organic biomarkers in marine and lacustrine sediments and atmospheric aerosols. We use a Dionex™ ASE™ 350 device to perform extraction and fractionation in one single analytical step. This significantly reduces the time of the analysis, and increases reproducibility while also diminishing sample handling time.
This new approach provides faster and more reproducible quantification of a wide range of organic biomarkers in different types of environmental matrices, which significantly increases the efficiency of the analysis and allows the study of a large number of samples inexpensively while reducing solvent waste and handling time.
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Acyclic Polyisoprenoid Hydrocarbons: Fundamental Regulators of the Archaeal Membrane?
Authors M. Tourte, V. Grossi, P. Schaeffer and P. OgerSummarySterols and hopanoids, the typical membrane regulators of Eukaryotes and Bacteria, are absent from Archaea, which might instead use acyclic polyisoprenoid hydrocarbons (APH). Although a few studies evidenced that APH do modulate membrane physicochemical properties as other membrane regulators, little is known about these intriguing compounds in the third domain of life. In an effort to elucidate APH distribution, physiological and adaptive functions, and biosynthetic pathway in Archaea, we collected all the literature data available and evaluated the APH composition of 65 archaeal species homogeneously distributed within the phylogenetic tree and ecological niches of Archaea. Fully saturated to fully unsaturated 30, 35, and 40-carbon long APH were detected in most species investigated, regardless of their phylogenetic position, lipid composition, or preferential environmental conditions, although the chain length could be correlated with growth conditions. Despite such a wide occurrence of APH in Archaea, only rare homologues of the eukaryotic and bacterial APH biosynthetic pathways were found. How they synthesize these compounds thus remains elusive and lipid analysis still prevails as the only mean to assess the production and functions of these essential archaeal membrane components.
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Mass Spectrometry Imaging of Varved Sediments of the Santa Barbara Basin Reveals the Wildfire History in Southern California
Authors S. Alfken, L. Wörmer, J. Wendt, A. Schimmelmann and K. HinrichsSummaryWildfire-related biomarkers monosaccharide anhydrides (Mas) formed during biomass burning were analyzed using the direct and extraction-free approach of mass spectrometry imaging (MSI) in varved sediments of the Santa Barbara Basin (SBB) in order to reconstruct the recent wildfire history in southern California’s hinterland. The resulting laser-based MA record, spanning a period from AD 1900 to 2009 with approximately monthly resolution, strongly matches the areal extent of recorded wildfires since AD 1950. Potential constraints of MSI with respect to pyrolytic interaction of the laser with lignocellular biomass in the sediment, as well as a closer comparison with conventional chromatographic methods for separation of MA isomers will be needed to implement MSI as an approach for high-resolution wildfire reconstruction.
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DOES TEMPERATURE AFFECT SOIL ORGANIC MATTER DECOMPOSITION AND DISSOLVED ORGANIC MATTER OPTICAL PROPERTIES?
Authors F. Ouedraogo, L. Denaix, M. Sourzac, C. Coriou, S. Bussiere, S. Millin, N. Janot, J. Cornu, N. Fanin and E. ParlantiSummaryCopper-based fungicides are potentially toxic to organisms because of their huge amounts in vineyard soils resulting from almost 150 years of massive use. Dissolved organic matter (DOM) depending on its quality can complex copper and influence its toxicity. DOM quality and quantity are related to soil organic matter (SOM) decomposition under the impact of environmental factors like temperature. We aimed in this study to assess the effect of temperature, depending on soil nature, on the quantity and quality of DOM originating from SOM mineralization. A 60-day incubation at 20°C and 30°C was conducted on two soils differing in type and C/N ratio. DOM absorbance and fluorescence and hydrolytic enzymatic activities were analyzed all along the experiment. The nature of soils affected the measured variables more than the temperature. Nevertheless, in the highest C/N soil, the hydrolytic enzymes activities decreased at t60 for the 20°C temperature suggesting a shift from hydrolytic to oxidative enzymes abundance. It is concluded that the difference between the two studied temperatures was not enough to observe clear changes on DOM properties and SOM decomposition, but that eventual effects could appear in a longer experience and more contrasted temperatures.
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Aromatic Hydrocarbons and Dibenzothiophenes from the Late Neoproterozoic Khatyspyt Formation (Siberian Platrofm)
Authors D. Melnik and T. ParfenovaSummaryThe Late Neoproterozoic Khatyspyt Formation from the northeast of the Siberian Platform (Khorbusounka River valley) is enriched with autochthonous organic matter (OM), which is exceptionally well preserved and has low thermal maturity (early oil window). This object is considered to be the one of the sources of bitumens in this area. The geochemical investigation of its rocks and OM remains an actual problem as a part of the regional geological works.
Current work is focused on the geochemistry of aromatic hydrocarbons and dibenzothiophenes of bitumens from the new collection of the Khatyspyt Formation. Phenanthrene and methylphenanthrenes, dibenzothiophenes and methyldibenzothiophenes, triaromatic and monoaromatic steroids were analysed.
New data suggest that the Khatyspyt OM could be regarded as typically aquatic similar to the Bazhenov and Kuonamka OM. The MPI-1 and Rv values confirm previous studies of saturated HCs and suggest early oil window maturity of the Khatyspyt OM. Thus, the Khatyspyt Formation could be regarded as a potential petroleum source rock and a source for bitumens deposits in the northeast of the Siberian Platform.
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Fluorescence Lifetime Evolution of Crude Oils During Pyrolysis Experiments
More LessSummaryWith increasing extent of oil cracking (Rc), the fluorescence lifetime evolution of crude oils can be approximately divided into two stages. They first increase at the early oil cracking stage with Rc < 40%, and then they begin to decrease at the late oil cracking stage with Rc > 40%. The change of fluorescence time of pyrolyzed oils is closely positively related to the variation in the fluorescence lifetime of aromatics (τaro) and the saturate/aromatic ratios (Rsat/aro) of pyrolyzed oils. Nevertheless, the oil cracking process can hardly cover up the differences in the fluorescence lifetime of the crude oils that have distinct genetic origins during the main oil cracking stage (i.e., Rc < 80%). In this sense, the fluorescence lifetime, along with other spectral parameters, may be used to distinguish crude oils and/or inclusion oils in the reservoirs that have been subjected to distinct thermal history.
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A Kinetic Modeling Approach to H2S Risk Assessment in the Pre-Salt Reservoirs in the Santos Basin
Authors I. Souza, G. Ellis, L.F. Coutinho, A. Ferreira, R. Diaz and A.L. AlbuquerqueSummaryThe pre-salt play in the Santos Basin contains giant oil and gas accumulations and is considered the largest petroleum discovery in the last decade. However, the fields contain non-hydrocarbon gases (e.g., CO2 and H2S) that bring technical challenges for exploration and production. Although H2S concentrations are quite low (15 to 180 ppmv), corrosion and environmental issues can arise, with higher costs required to mitigate these problems. Consequently, it is important to identify the generation processes of these gases to improve estimates of the required investments during the initial phases of the projects. Santos Neto et al. (2013) suggested that the main H2S generation process in the pre-salt reservoirs in the Santos Basin is thermochemical sulfate reduction (TSR), mainly based on the sulfur isotopic composition of H2S, oils, and anhydrites. Additional TSR proxy analyses were conducted (compound-specific sulfur isotope analyses — CSSIA and thiadiamondoid quantification) and these subsequent results suggested that TSR may not be involved. To constrain the possible origins of H2S, we have modelled in situ TSR in low temperature carbonate reservoirs (∼100°C) using published kinetic parameters.
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Thermophilic Archaea Activate Liquid Alkanes Using Divergent Methyl-Coenzyme M Reductases
Authors H.S. Zehnle, R. Laso Pérez, A. Boetius and G. WegenerSummaryHere, we introduce two members of the new archaeal group Alkanophagales. Archaea belonging to this group are closely related to ANME-1 and Syntrophoarchaeales. We have enriched these thermophilic archaea using anoxic slurries from Guaymas Basin sediments, sulfate as electron acceptor, and liquid medium-chain alkanes as electron donors. The Alkanophagales representatives oxidize these alkanes anaerobically using divergent methyl-coenzyme M reductases. They shuttle the electrons released during alkane oxidation to Thermodesulfobacteria, which use them to reduce sulfate to sulfide. Thermodesulfobacteria constitute a new partner bacterium for anaerobic alkane-oxidizing archaea.
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INTENSE WARMING ON HIGHLAND SUMATRA DURING THE MID HOLOCENE SEA-LEVEL HIGHSTAND
Authors P. Hällberg, A. Cortizas, A. Hapsari, H. Rifai, S. Eisele, C. Bouvet de la Maisonneuve and R. SmittenbergSummaryThe Indo-Pacific Warm Pool (IPWP) climate and related monsoon systems directly affect approximately half the global population, and knowing their past behaviour is crucial for the understanding of our climate system and potential future change. However, few terrestrial proxy records exist in the tropics to resolve the details of IPWP climate variability.
Here we present a 12,200-year record from a peatland situated in the western IPWP region situated at 1500m altitude in highland Sumatra, a region with high influence from the Indian Ocean. We use branched glycerol dialkyl glycerol tetraethers (brGDGTs), bulk and compound-specific stable isotopes, Fourier-Transform Infrared (FTIR) analysis, carbon accumulation rate and long-chain alkane distributions, augmented by pollen and geochemical (XRF) analysis, to reconstruct past temperature, precipitation and environmental changes.
We find that not only the Younger Dryas, but also the early Holocene was still cold and affected by a greater ENSO variability. Around 8 ka BP the climate started to warm considerably, ENSO was reduced and temperatures were as much as 3˚C warmer than today around 5 ka BP. This was followed by a temperature decrease with an abrupt shift to colder temperatures and greater influence of El Nino after 3ka BP.
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