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30th International Meeting on Organic Geochemistry (IMOG 2021)
- Conference date: September 12-17, 2021
- Location: Online
- Published: 12 September 2021
1 - 100 of 279 results
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PETROLEUM SYSTEM OF DUVA OIL AND GAS FIELD IN NORTHERN NORTH SEA, NORWAY
More LessSummaryThe Duva oil and gas field is located at ca. 5 km northeast of the Gjøa field in the Northern North Sea. The reservoir contains oil and gas in a turbiditic sandstone of the Early Cretaceous Agat formation. Highly waxy oils were collected, and its geochemical characteristics were investigated by GC and GC-MS analyses. We performed position-specific isotope analysis (PSIA) on a gas sample from the Duva field to identify the effective source rock of the gas. 2-dimensional basin modelling was conducted to understand the petroleum system including complex migration and accumulation processes of the Duva field. The abnormally waxy oil in the Duva field possibly formed by the large input of terrestrial organic matter into the Upper Jurassic marine source rocks and/or the evaporative migration fractionation based on the biomarkers and carbon isotopic compositions. Intramolecular carbon isotopic compositions of propane in the gas sample suggested that the gas in the Duva field was generated from coals in the Middle Jurassic or older. A late charge of the gas derived from the coaly source rock into an initial oil accumulation may have caused the evaporative fractionation resulting in the formation of the waxy oil in the Duva field.
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Role of Bitumen and Nsos During Thermal Maturation of a Lacustrine Type-Ii Shale in Semi-Open Pyrolysis Experiment
More LessSummaryBy taking the Chang7 shale in the Ordos Basin of China as an example, the decomposition pathway of lacustrine Type-II kerogen was studied. Results show obvious characteristics of concurrently generation of bitumen and oil and simultaneously generation of NSOs and HCs during the initial kerogen decomposition. The results not only contradicts with product-precursor relationship between the bitumen and oil of lacustrine Type-I and marine Type-II kerogen, but also negates the sequential reaction model between NSOs and HC of lacustrine Type-I kerogen, marine Type-II kerogen, and Type-III lignite.
The reaction process of the Chang7 shale under semi-open pyrolysis conditions follows the “alternate pathway”, in which hydrocarbons can be formed immediately from kerogen in parallel with NSOs and the formation of the two species are controlled by bond-breaking reactions independent of each other. From this point of view, the Chang7 kerogen is likely to contain sufficient branched structures that bond-breaking has a high possibility of generating HC at the onset of pyrolysis. The mechanism not only applies to the Chang7 shale, but also can be extended to source rocks of the same kerogen type worldwide. This work has broadened the understanding of the decomposition pathway of a less studied kerogen type.
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Chemical Structure Evolution of Lacustrine Type-Ii Kerogen Under Semi-Open Pyrolysis as Investigated by 13C Nmr and Ft-Ir
More LessSummaryThis study aim to investigate the structural changes of a lacustrine Type-II kerogen, by taking the seventh Member of the Triassic Yanchang Formation in the Ordos Basin (Chang 7 Shale) as an example. Integrated analysis including elemental analysis, programmed pyrolysis (Rock-Eval), FT-IR, and 13C NMR were conducted on the unheated and post-pyrolysis rocks and kerogens.
Results show that before the peak hydrocarbon-generating stage (Ro < 0.6%), defunctionalization of oxygen-containing functional groups, which generates water, CO2 and NSOs, occurs simultaneously with the detachment of short aliphatic side chains and small aromatic rings, which generates volatile fractions (C6-C14, C15+ sat and C15+ aro), suggesting that the Chang7 kerogen is highly branched. During the peak hydrocarbon-generating stage (0.6–1.09 %Ro), the concurrent breakage of weak cross-link bonds and long aliphatic chains lead to the simultaneous peak generation of liquid hydrocarbons and NSOs, indicating the highly cross-linked features of the Chang7 kerogen. After the peak hydrocarbon-generating stage (Ro > 1.09%), the reactions in the previous two stages produce a highly aromatic kerogen. The increased aromaticity of the highly matured kerogen is likely to be caused by aromatization or dehydrogenation of hydroaromatics and coking of aromatic bitumen, not by fusing or condensation of aromatic rings.
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GEOCHEMICAL CHARACTERISTICS OF ORGANIC MATTER IN THE ACHIMOV DEPOSITS OF WESTERN SIBERIA AND THEIR OIL AND GAS POTENTIAL
By S. PunanovaSummaryThe report considers the geochemical features of the Achimov deposits of the West Siberian oil and gas basin, occurring in the lower Lower Cretaceous. The Neocomian oil and gas complex in Western Siberia has been studied relatively fully, but the geochemical features of the Achimov deposits continue to remain insufficiently studied. The Achimov strata lies at a depth of 2500–4000 m and is represented by layers of dense fine-grained sandstones with clay-carbonate cement, separated by interlayers of clays of various thicknesses (up to 10–15 m). A characteristic feature of the Achimov deposits is the clinoform structure of the traps, lithological inconsistency, and variable thickness. The presence of source deposits and the degree of their catagenetic transformation make it possible to consider the Achimov productive complex as completely independent. The OM of the Achimov deposits is characterized by moderate catagenesis and mixed sapropelic-humus composition.
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Trace Elements of Naphthides as Indicators of Geochemical Processes
By S. PunanovaSummaryThis report highlights the following aspects of the trace element (TE) composition of naphthides: 1. genetic relationships of bitumoids with the composition of generated oils; 2. dynamics of changes in the TE composition of naphthides during catagenic and hypergenetic transformations; 3. correlation dependences of the TE compositions of naphthides with the composition of various substances. The composition of the TE of oils and bitumoids has long been successfully used in petroleum geochemistry for solving various geological and geochemical problems. That is why the use of data on the TE composition of naphthides is relevant and well-grounded.
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TRACE ELEMENT COMPOSITION OF NAPHTHIDES IN LIGHT OF THE PERIODIC LAW OF CHEMICAL ELEMENTS
By S. PunanovaSummaryThis report discusses the features of the distribution of trace elements (TE) in naphthides in connection with the Periodic Table of D.I. Mendeleev. There are several generally accepted geochemical classifications of elements based on this Periodic Law. More than 60 elements have been identified in oil and its derivatives. Only technical limitations prevent the detection of the other elements in D.I. Mendeleev’s Periodic Table of the Elements within oils. The concentrations of these elements are low, but they carry important information. In petroleum geochemistry, for Zn, Br, Mn, Cu, I, As, B, F, Pb, Ti, V, Cr, Ni, Sr and other elements occurring in living matter from 1 to 100 ppm, the term “Trace elements”, or “Spurenelementen”, has become widely appropriated.
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Applications of Higher Diamaondoids within and Outside of the Petroleum Industry
Authors J. Dahl, J.M. Moldowan and R.M.K. CarlsonSummaryThe recent availability and property determination of petroleum-derived higher diamondoids has led to a number of applications and potential applications both within and outside of the petroleum industry. These include: correlation of highly-mature fluids, correlation of mixed-maturity oils, photo-emitters, field emitters, seeds for growing small diamonds with color centers for quantum information, pharmaceuticals, components in new polymers, components in lithium-ion batteries and catalysts. This presentation is an overview of these applications and the physical properties leading to them
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Identifying Plant Wax Inputs in Lake Sediments Using Machine Learning
Authors M. Peaple, J. Tierney, D. McGee, T. Lowenstein, T. Bhattacharya and S. FeakinsSummaryWe trained models to identify plant type based upon modern leaf wax chain length distributions. We then applied these models to ancient waxes extracted from a core collected from Searles Lake, California, USA, to reconstruct paleovegetation. We validated our models by comparing our vegetation results to the ACE index, a proxy for lake salinity also measured from lake core samples.
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Light Hydrocarbons and Their Message on Geochemistry of Oils and Condensates from the Bovanenkovskoye Field (West Siberia)
Authors A. Burukhina and E. FursenkoSummaryThe studied Bovanenkovskoye oil-gas-condensate field is located at the Yamal Peninsula – in the north of West Siberia, where a new gas-production centre is being formed. The aim of the study is to conduct geochemical type assignment of oil (5) and condensate (10) samples from the Lower Cretaceous (K₁al – 2, K₁a – 3, K₁g – 3), Middle (J₂bt – 3, J₂b – 3), and Lower Jurassic (J₁p – 1) deposits, using data about their properties and composition (distribution of n-alkanes, i-alkanes, steranes, terpanes, arenes, and, mainly, of light hydrocarbons C₄–C₈). In the presented research, the use is made of GC and GC/MS analyses of crude oils (condensates) and their hydrocarbon fractions. The obtained results suggest the hydrocarbon formation in the Bovanenkovskoye field from a single center of oil and gas generation due to the terrestrial organic matter of the Lower and Middle Jurassic strata (Malyshevka, Layda formations) and a significant contribution of the aquatic organic matter from the Upper Jurassic strata (Bazhenov formation) to the generation of the Aptian condensates.
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GEOCHEMISTRY OF PETROLEUM RESINS AND ASPHALTENS BASED ON FLASH-PYROLYSIS PRODUCTS
Authors E. Fursenko, A. Burukhina and K. DolzhenkoSummaryThe objects of the research are resins and asphaltenes (RAS) extracted from West Siberian oils. The obtained results reveal the genetic affinity of hydrocarbon fractions and the RAC of the studied oils.
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Organic Matter Occurrence and Alteration in the Uranium-Rich Alum Shale Formation: Implications for Microbial Activity
More LessSummaryThe Early Palaeozoic Alum Shale Formation in northwestern Europe is rich in uranium up to several hundreds of ppm. Despite the absence of higher land plant precursors, the primary Type II kerogen in the Alum Shale has an abnormally strong aromatic character even at low thermal maturities, probably due to α-particle bombardment.
FT-ICR-MS data reveal that the macromolecules in the uranium-rich Alum Shale samples are less alkylated than less irradiated counterparts, and that oxygen containing-compounds are enriched in the uranium-rich samples but are not easily degradable into low-molecular-weight products due to irradiation-induced crosslinking.
Despite strong organic matter alteration, CO2 and CH4 are formed using U-rich samples in incubation experiments, and DNA-based high-throughput sequencing allows a detailed phylogenetic characterization of the indigenous microbial communities with implications of an uranium-adapted biosphere.
The alteration of macromolecular organic matter in the Alum Shale Formation is suggested as an Earth analogue of the Martian surface, in response to α-particle irradiation. Especially a comparison of potential habitats on the Martian surface with Kolm nodules of the Alum Shale in terms of irradiation dosage and organic geochemical characteristics reveals that they have received similar levels of irradiation.
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The Effect of Elemental Sulfur on the Thermal Evolution of Steroids
More LessSummarySteroids are one of the most important families of biomarkers, and have been widely used in petroleum exploration, paleoenvironment reconstruction and the research of eukaryotic evolution in early Earth, etc. The general evolution pathways of natural steroids were initially speculated on from their distribution in geological samples. Previous researchers further clarified the evolutionary pathways of steroids through laboratory thermal simulation experiments. However, the role of sulphur/sulphur-bearing compounds on the thermal evolution of steroids was still not well understood. We therefore carried out research on the thermal evolution pathway of steroids with and without elemental sulfur using gold tube pyrolysis experiments. The results show that elemental sulfur significantly accelerated the thermal evolution process of steroid compounds, and can induce aromatization starting with the C-ring monoaromatic steroids. The common coexistence of sterols, sterenes, steranes and aromatic steroid compounds in many immature geological samples may also be the result of the presence of sulfur. The isomerization of steranes was significantly different with and without sulfur. Therefore, when using sterane isomerization parameters to evaluate the maturity of geological samples, it is necessary to take more factors into consideration such as the lithofacies, including the presence of sulfur.
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A Comparison of Maturity Between Oil and Source Rock in the Shale-Oil System of the Qingshankou Formation, Songliao Basin
More LessSummaryDetermination of oil maturity is of great significance for understanding the origin and evolution stage at which the oil is generated, and is one of major topics in petroleum geochemistry research. Due to oil migration, oils in reservoirs most likely are mixtures of oils generated at different thermal maturities or by different source rocks, and it is usually hard to establish relationship between source rock and oil with respect to thermal maturity. In this paper, source rock maturity was compared with that of intra-source oil (i.e. shale oil), providing preliminary implications for further study.
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Novel Approach to Reservoir Continuity Evaluation Through Gc-Ms Geochemical Fingerprinting
Authors P. Franco, I. Colombo and R. GalimbertiSummaryGeochemical fingerprinting of reservoir fluids represents a widely adopted methodology to address questions related to reservoir geochemistry, such as the assessment of continuity through the hydrocaron pool. This technique is based on the general assumption that disconnected reservoirs will produce oils with significantly different molecular fingerprints; therefore, the assessment of such differences can be used to infer the presence of compartmentalization. Currently, one of the main limitations of this technique resides in the need of representative reservoir fluids to test, which are often unavailable. The present work deals with the develompment of a GC-fingerprinting approach aimed to the analysis of residual oil in cuttings, wich allows to overcome the limitation related to the lack of proper reservoir oil samples. The main challenges, possible solutions and current limitations of this approach will be presented, along with a representative case history showing the successful application of this methodology and its potential.
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How Do the Groundwater Level Fluctuations May Affect the Remobilization of Lnapls?
Authors A. Cavelan, P. Faure, C. Lorgeoux, S. Colombano, J. Deparis, H. Davarzani, N. Enjelvin, C. Oltean, A. Tinet and F. GolfierSummaryLight non-aqueous phase liquids (LNAPLs) are one of the most common sources of soil pollution worldwide. The Intergovernmental Panel on Climate Change (IPCC) predicts a significant increase of groundwater level fluctuations' intensity by 2100 that may greatly favor the remobilization of these contaminants in the environement. Yet, the effect of groundwater tables fluctuations on the LNAPL mobilization is not fully understood. To this aim, a new original experimental system combining in situ physical-chemical, geochemical, and indirect geophysical measurements was developed at the GISFI station, Homécourt, France to assess the effect of the groundwater level variations dynamic, under current and climate change conditions, on the LNAPL remobilization. Attention will be paid, especially, to the evolution of the concentration and composition of the dissolved LNAPL phase over time. Measurement, and monitoring of the pure LNAPL phase thickness and chemical composition variation will be also monitored. Numerical simulations of the LNAPL transport through the contaminated soil will also be carried out. These experiments should provide a better understanding of the fate of these hydrocarbons at contaminated soils and thus, a better assessment of the environmental risks associated with these contaminated sites and their evolution in the climate change context.
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Occurrence and Identification of Five Series of Benzohopanes in Sediments
Authors L. Jiang, L. Li, H.P. Nytoft and S.C. GeorgeSummaryBenzohopanes are common compounds in sediments and crude oils. Three series of benzohopanes have been reported so far, but we have found two new series of benzohopanes in lacustrine sediments. This abstract exhibits the occurrence and identification of five series of benzohopanes in lacustrine shales, oil shales and mudstones.
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Study on oil source in the Jiufengshan Formation of the Dayangshu Basin, China
More LessSummaryDayangshu Basin is located in Eastern Inner Mongolia Autonomous Region, China. It is a late Mesozoic basin that is covered by volcanic rocks. The tectonic movement is violent. Fault activities control the formation and development of the basin. Volcanic activity runs through the whole process of basin formation. It is of great significance that study on the characteristics of source rocks and oil-gas sources in the Dayangshu Basin for evaluating the oil-gas exploration potential, understanding the oil-gas generation and evolution of the volcanic strata in the eastern basin of China.
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The Geochemical Characterisitics and Origin of Ordovician Ultra-Deep Natural Gas in Shuntuoguole Area, Nw China
More LessSummaryAll the natural gases in Shuntuoguole area are oil-type gases, in which the gases in SB area are wet gas with kerogen-cracking dominated, whereas the gases in ST, SN, GL, GC areas are dry gas originated from oil-cracking. Both the wet and dry gases in Shuntuoguole area are sourced from Lower Cambrian Yuertusi Formation.
The distribution of two types natural gas is correlated with the present strata temperature and (or) paleo-temperature of Ordovician. The present strata temperature and paleo-temperature of Ordovician in SB area ranged from 150∼160℃, 170∼180℃, unreached the temperature of oil-cracking in large scale. However, the paleo-temperatures of Ordovician in ST, SN, GL and GC areas have exceeded 180℃ and present strata temperatures are high with temperature about 200℃, resulting the paleo-oil reservoir cracking in large scale. Thus, from SB to ST to SN to GL to GC areas, the fluid phase changed from light oil to volatile oil to condensate to dry gas phase gradually.
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Geochemical Analysis of the Q Source Rocks of Oman: A 40-Year-Old Mystery.
Authors M. Al Ghammari, G. Siavalas, A. Bell and M. SpaakSummarya geochemical study on source rocks found in the eastern flank of Oman Ghaba Basin and effort to correlate this source rock to Oman oils families. we believe that this source rocks is the source for the well known Q oil family in Oman which has been known since 40 years but no source rocks were linked to it.
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Molecular Significance of Rock-Eval® S2 Pyrograms
Authors J. Jacob, F. Delarue, Y. Copard, C. Le Milbeau, L. Grasset and P. BrockmannSummaryWe here present original results acquired through a simple setup that allows obtaining molecular explanations of the mathematical deconvolution of Rock-Eval S2 pyrograms. This approach provides clues to the intimate nature of organic matter and bridges a gap between bulk and molecular information.
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MOLECULAR BIOMARKERS IN FOSSIL AND MODERN CARNIVOROUS COPROLITES
Authors C. Gauthier, J. Jacob and J. BrugalSummaryWe here present new results on biomarkers preserved in fossil and modern coprolites from carnivorous animals
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FIRST INSIGHTS INTO ORGANIC GEOCHEMISTRY OF THE LATE NEOPROTEROZOIC KHARAYUTEKH FORMATION, NORTHEASTERN SIBERIA
Authors T. Parfenova and D. MelnikSummaryThe results of the first geochemical investigation of the organic matter from the Late Neoproterozoic Kharayutekh Formation widely distributed in the Kharaulakh Ranges of northeastern Siberia are presented. Data shows that the Middle Kharayutekh Member can be regarded as a potential source rock. Natural bitumen and/or gas deposits associated with the realisation of the hydrocarbon generative potential of the Kharayutekh rocks can be found in the Arctic region of Northeastern Siberia.
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CATAGENETIC EVOLUTION OF THE COMPOSITION AND STRUCTURE OF ASPHALTENE COMPONENTS OF ORGANIC MATTER
Authors L. Borisova and I. TimoshinaSummaryThe revealed tendency of changes in the elemental and structural-group composition of asphaltene components of the organic matter of different origins at different stages of transformation is concerned with:
- the formation of the composition and structure of OM asphaltenes occuring at the stage of diagenesis, which are largely predetermined by the initial substrate of the organic matter;
- the identified trend for polymer condensation changes in both genetic types of OM at the initial stage of thermocatalytic transformations;
- the directed process of asphaltene graphitization taking place during catagenesis, which is accompanied by a decrease in hydrogen content, an increase in the proportion of aromatic and condensed structures among them, and is characterized by a decreasing role of alkyl and cycloalkyl hydrocarbon substituents of their molecules.
A linear dependence of the change in composition and structure during thermocatalytic transformations which will make it possible to develop catagenesis grades based on the data obtained from the study of asphaltenes within the entire range of stages.
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Ecosystem and Hydroclimate Conditions from a New Early Human Site at Olduvai Gorge (AGS, BED I, 1.84 Ma)
More LessSummaryIn this study, we focus on a newly discovered Early Pleistocene archaeological site – AGS (Alberto Gómez Site) – at Olduvai Gorge in Northeast Africa to identify coeval landscape resources via a multi-proxy perspective. We explore the distribution of four major compound classes (n-alkanes, n-alcohols, n-alkanoic acids, and sterols) and leaf-wax δ13C-δD compositions of 24 paleosoil samples excavated from a 24 m2 archaeological transect at AGS. Our multi-proxy geochemical interpretations of the Olduvai Zinj-Paleolandscape at 1.89 Mya reveal that AGS was located near the river/lake margins and was dominated by C3 aquatic plants and C4 grasses. Given the mosaic patchy ecosystem across the Zinj-Paleolandscape soil horizon and the molecular fossils studied here at AGS, we hypothesize that hominins at Olduvai Gorge, 1.9 ma years ago, selected the locations for their main activities conditioned by the presence of water resources within the landscape.
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BHT-x: Constraining its Application as a Lipid Biomarker for Marine Anammox Using a Modern Water-Column Oxygen Gradient
Authors Z. Van Kemenade, L. Villanueva, E. Hopmans, P. Kraal, H. Witte, J. Sinninghe Damsté and D. RushSummaryRecently it was discovered that members of the marine anaerobic ammonium oxidizing (anammox) genus, ‘Ca. Scalindua spp.’, uniquely synthesize a stereoisomer of bacteriohopanetetrol (‘BHT-x’). The ratio of BHT-x over total BHT (ubiquitously synthesized by diverse aerobic bacteria) has been suggested as a proxy for water column anoxia. BHT-x hereby has the potential to act as a biomarker for anoxia as well as extend the sedimentary biomarker record of marine anammox. In this study, we have investigated the water column distributions of BHT-x and the BHT-x ratio in suspended particulate matter (SPM) samples at 15 stations along the large oxygen gradient in the Benguela Upwelling System (BUS). Distributions were compared to distributions of intact polar (IPL) ladderane phospholipids, ladderane fatty acids (FAs) and the presence of the Ca. Scalindua 16S rRNA gene reads. The similar distributions of BHT-x, ladderane FAs and the relative abundance of Ca. Scalindua 16S rRNA genes confirms the suitability of BHT-x as a biomarker for water column anammox in the sedimentary record of upwelling systems. Nevertheless, we suggest including the BHT-x ratio when interpreting anammox based on lipid biomarkers, as this study confirms that low abundance of BHT-x may not always reflect in situ water column anammox.
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ANALYSIS OF NON-DERIVATIZED BACTERIOHOPANEPOLYOLS USING UHPLC-HRMS2: A FURTHER STEP TOWARDS ENVIRONMENTAL LIPIDOMICS.
Authors E. Hopmans, N. Smit, R. Schwartz-Narbonne, J. Sinninghe Damsté and D. RushSummaryWe describe the analysis of non-derivatized bacteriohopanepolyols using UHPLC coupled to high resolution MS. We demonstrate the capabilities of the method by discussing the results of the analysis of a soil sample taken near an active terrestrial methane seep. We were able to identify 131 individual BHPS. We also identified tentatively identified several novel BHPs
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Organic Geochemistry and Source Rock Potential of the Bazhenov Black Shales form the West Siberian Basin, Russia
Authors L. Burnaz, A. Baniasad, A. Kalmykov, G. Kalmykov and R. LittkeSummaryThe West Siberian Basin (WSB) constitutes the largest petroleum province in Russia. The oil accumulations in the WSB are mainly sourced by the Upper Jurassic Bazhenov Formation (BF). This study aims to provide information on the geochemical and petrographic characteristics of a representative sample set of the siliceous BF black shales from the Southwest Ob region in the southwestern WSB. On 39 samples, comprehensive analyses and observations were performed, including total organic, inorganic carbon (TOC and TIC) and total sulfur content (TS) measurement, Rock-Eval pyrolysis, organic petrography and molecular geochemistry. The samples show excellent source rock potential and oil-prone source rock characteristics, mainly containing organic material that can be assigned to Type II kerogen. The black shales were deposited in a marine depositional environment with periodically anoxic conditions. The evaluation of maturity sensitive properties imply that the 39 samples are affected by varying degrees of thermal maturity covering the catagenesis stage from the onset to the end of the oil window.
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Evaluation of Anhydrosugars as a Molecular Proxy for Paleo-Fire Activity: A Case Study from Peloponnese, Greece
More LessSummaryAnhydrosugars like Levoglucosan (LVG) are produced upon incomplete combustion of cellulose, and can act as molecular markers for biomass burning. In this multi-proxy study from the Agios Floros wetland, Pelopponese, Greece, we found that wetter conditions - causing better organic matter preservation - was the dominant control on LVG concentrations. In contrast, the LVG profile was reciprocal to the microcharcoal record and to other proxy evidence for dryness, e.g. based on leaf wax hydrogen isotopes. We conclude that an approach using several proxies, both for fire, hydroclimate and vegetation change, is needed when aiming to reconstruct past biomass burning from wetland ecosystems with a strongly seasonal climate as in the Mediterranean. Our study also relates significant fire activity between 4400-2800 cal.yr BP to the Bronze Age period that saw intense human environmental interaction and climate change.
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Decoupling of temperature and hydroclimate in North China since late Miocene
More LessSummarywe separate the air temperature and hydrological records extending back six million years (Ma) on the basis of lipid biomarkers preserved in a terrestrial drill core (XA3 drill core) in North China, East Asia.
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Assessing the Impact of Magmatic Activity on Hydrocarbon Generation in the Namibe Basin (ANGOLA)
Authors E. Fiordalisi, B. Van Dongen, J. Moore, J. Hennissen, I. Sharp, R. Dixon and S. SchröderSummaryAssessing the impact of magmatic activity on source rock maturation and hydrocarbon generation is highly critical when evaluating the prospectivity of volcanically influenced sedimentary basins. An integrated organic geochemistry and petrographic study was conducted on a variety of bitumen samples and candidate source rocks from the Namibe Basin of Angola, which was affected by multiple magmatic events. Analyses suggest that multiple processes of hydrocarbon generation and emplacement took place, including locally forced thermal maturation of otherwise immature source rocks and source rock thermal maturation via conventional basin-scale burial processes. Imminent future analyses include vitrinite reflectivity and 1-D modelling to characterise the basin thermal regime and quantitatively assess the impact of magmatic activity on source rock maturation and hydrocarbon generation.
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Lipidomics of Environmental Microbial Communities
Authors S. Ding, N.J. Bale, E.C. Hopmans, L. Villanueva, M. Arts, S. Schouten and J.S. Sinninghe DamstéSummaryStructurally diverse, specialized lipids are crucial components of microbial membranes and other organelles and play essential roles in ecological functioning. The detection of such lipids in the environment can reveal not only the occurrence of specific microbes but also the physicochemical conditions to which they are adapted to. Traditionally, liquid chromatography coupled with mass spectrometry allowed for the detection of lipids based on chromatographic separation and individual peak identification, resulting in a limited data acquisition and targeted at certain lipid groups. Here, we explored a comprehensive profiling of microbial lipids throughout the water column of a marine euxinic basin (Black Sea) using ultra high-pressure liquid chromatography coupled with high-resolution tandem mass spectrometry (UHPLC-HRMS/MS). An information theory framework combined with molecular networking based on the similarity of the mass spectra of lipids enabled us to capture lipidomic diversity and specificity in the environment, identify novel lipids, differentiate microbial sources within a lipid group, and discover potential biomarkers for biogeochemical processes. The workflow presented here allows microbial ecologists and biogeochemists to process quickly and efficiently vast amounts of lipidome data to understand microbial lipids characteristics in ecosystems.
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PY-GC×GC-TOFMS: A POTENTIAL TOOL FOR THE MOLECULAR CHARACTERIZATION OF FOSSIL BIOPOLYMERS
Authors R. Umamaheswaran, S. Dutta and S. KumarSummaryIn recent years, there has been an increase in interest in the preservation of nitrogen-bearing biopolymers in organic remains from deep time, reflected by the increase in reports of such preservation. However, there has also been controversy regarding the veracity of these reports. Here, we propose a method to independently characterize the molecular structure of various biomacromolecules, by using pyrolysis comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (Py-GC×GC-TOFMS). We initially analyze G. Prisca, Tasmanites and fossil resin to demonstrate efficacy of this technique. We then analyze industry standards of chitin, collagen and fossil melanin to identify characteristic compound distributions and to distinguish between the three nitrogen-bearing biomacromolecules. We then apply the technique to an Eocene mammal bone.
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USING LOGGING DATA TO ESTABLISH A METHOD OF S1 CALCULATION AND EVALUATE OIL-BEARING PROPERTIES OF SOURCE ROCKS, SONGLIAO BASIN
By Z. XiaochangSummaryThe calculation model is established by using interval transit time and resistivity curves to calculate the rock pyrolysis parameter S1, so as to evaluate the oil-bearing property of source rocks. S1 of 168 wells are calculated by this method, and 71 wells of them have been measured S1 from core samples. Comparing the difference between the average value of calculated S1 and measured S1,it can be seen that the more samples measured S1 in a single well, the smaller the difference between the calculated S1 and the measured S1. By drawing several well-connected sections and S1 plans, the changing trend of oil-bearing property of source rocks in study area is definited, and the favorable oil-bearing areas are pointed out. This S1 calculation method is suitable for the oil-bearing evaluation of regional source rocks and has guiding significance for exploration.
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INFLUENCE OF CLASTIC MINERALS ON THE PHASE BEHAVIOR OF HYDROCARBON
More LessSummaryTo predict the phase state of the petroleum in these deep-buried reservoirs accurately would be of great benefit in further exploration and development. However, the influence of reservoir minerals on phase behaviors of crude oil in deeply buried reservoirs remains poorly understood. Here we report on our investigation of the influence of common siliceous minerals (quartz, feldspar, montmorillonite, illite) on the cracking and phase behavior of crude oil. We demonstrated that the common minerals found in clastic oil reservoirs have complicated influences on the thermal cracking behavior of crude oil. Further analyses showed that the PVT phase characteristics of the crude oil can also be related to the minerals present. Clay minerals, and especially montmorillonite, significantly change the dew point temperature and bubble point pressure. However, when Ro values exceed 2.0%, even when montmorillonite content reached 40 wt. %, the phase behavior of crude oil does not change significantly.
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INFLUENCE OF CARBONATE MINERALS ON THE PYROLYSIS BEHAVIOR OF HYDROCARBON
More LessSummaryThe knowledge of the influence of minerals on oil cracking behaviors will be benefit to the predicting of physical properties (such as density, viscosity and phase state) and chemical composition of petroleum. Though considerable amounts of carbonate reservoirs are dolostone reservoirs, the role of dolomite on the thermal evolution of hydrocarbons is still not well understood. To investigate the influence of dolomite, a series of laboratory simulation experiments of oil with various carbonate minerals, including calcite, magnesite, and dolomite were conducted and analysed here. This study demonstrate that two common carbonate minerals (calcite and dolomite) have different influences on the oil cracking behavior and PVT phase of oil in carbonate conditions. Calcite had limited influences on the thermal cracking behavior of crude oil, with slightly reduction of the yield of C6-13, while dolomite strongly affected the yield of C1-5, C6-13 and H2S. The presence of dolomite seems to promote the generation of H2S and the cracking of C1-5.
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Biomarker Signatures in Cretaceous Sediments of An Island Continent
Authors D. Niyolia, S. Dutta and B. SamantSummaryThe unique position of Indian plate during the Early Cretaceous draws our attention to study the paleofloral diversity on the Indian continent. An attempt has been made to investigate the distribution of biological markers of Early Cretaceous shale of Krishna Godavari (KG) Basin, Early Cretaceous coal and shale of Kutch Basin and Late Cretaceous shale from Deccan Intertrappean sediments. The terpenoid composition of Early Cretaceous samples of Kutch and KG Basin is represented by the significant occurrence of diterpenoids in both aliphatic and aromatic fractions. However, the Late Cretaceous sediments are dominated by angiosperm derived triterpenoids. Therefore, the present study clearly suggests that the angiosperms evolved in the island continent during the Late Cretaceous.
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Molecular and Isotope Composition of Biomarkers in Immature Oil Shale and its Liquid Pyrolysis Products (Open and Closed System)
Authors G. Gajica, A. Sajnovic, J. Schwarzbauer, A. Kostic, B. Jovancicevic and K. StojanovicSummaryThe molecular and isotopic composition of biomarkers in initial bitumen isolated from raw immature oil shale samples from the Lower Miocene Aleksinac Basin (Serbia) and liquid products (LPs) obtained by pyrolysis in open (OS) and closed systems (CS) are studied. The influence of pyrolysis type and variations of kerogen type on biomarkers composition and their isotopic signatures in LPs is determined.
The molecular composition of the LPs from the OS pyrolysis is very similar to those in initial bitumen, independently on kerogen type. The LPs from the CS pyrolysis have the distributions of biomarkers similar to those in crude oils generated in an early to main stage of “oil window“. The biomarker data suggests that mixed type I/II kerogen attained slightly higher maturity level by the CS pyrolysis than type I kerogen. The isotopic signatures of n-alkanes in LPs obtained by the OS pyrolysis are isotopically lighter than in initial bitumen, independently on kerogen type, whereas in liquid products from the CS they become heavier; showing more pronounced difference for type I kerogen. The results indicate that δ13C data should be used with caution in interpretation of samples having different maturity and particularly of LPs obtained by different system pyrolysis.
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Hydrocarbons in Intertidal Deposits of the Norwegian and Russian Coast of the Barents Sea
Authors A. Kursheva, I. Morgunova, V. Petrova, I. Litvinenko, G. Batova, A. Maltseva, E. Golikova and P. RenaudSummaryThe complex study of the organic matter (OM) and HC molecular markers in sediments and soils of the Arctic littoral is an important step to the environment protection. The study of polycyclic aromatic HCs (PAHs) is of particular interest due to their toxicity and high content in the main anthropogenic pollutants (oil, fuels, combustion products etc.).
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Organic Matter in Bottom Sediments of the Shelf Part of the Laptev Sea as an Indicator of Sedimentation (Expedition 2018)
Authors I. Litvinenko, A. Kursheva, V. Petrova, G. Batova, I. Morgunova and E. GusevSummaryThe main idea was to investigate the composition of hydrocarbon (HC) molecular markers, as indicators of the origin of sedimentary material. The object of the study is bottom sediments collected from latitudinal transects stretching along the outer edge of the shelf and the upper continental slope of the Laptev Sea. Sampling was made during the research cruise of FSBI VNIIOkeangeologia in 2018 (R/V Ivan Petrov). The molecular composition of the DOM indicates a significant input of terrigenous components of diagenetic maturity degree to the sediments of the region. Moreover, the input of molecular markers characteristic for the bacterial activity (possibly methanotrophic) is detected in some sediments (n-C16 and n-C18 predominate in composition of the lower molecular weight n-alkanes; the tricyclic terpanes ratio (2(C19+С20)/(C23+С24+C25+С26) < 1). The inflow of the reduced Atlantic waters with the along-slope currents and the processes of bottom and coastal abrasion determine the contribution of the transformed marine DOM to the sediments of continental margin.
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STABLE ISOTOPE SIGNATURES FROM SUBSTRATE UTILIZATION BY DIFFERENT FUNGAL ECOTYPES VIA A DUAL-SIP APPROACH
Authors S. Jabinski, W. De Melo Rangel, F. Lorenz and T.B. MeadorSummaryEach year, roughly one-sixth of atmospheric carbon (115 Pg C) is cycled through terrestrial vegetation, channeled into the soils below, and respired back to CO2 ( IPCC, 2007 ). However, predicting the reactivity and CO2 buffering capacity of soil systems and thus the carbon-climate feedback in terrestrial ecosystems is limited by poor understanding of the accessibility and turnover of “recalcitrant” organic matter in soils ( Lehmann & Kleber, 2015 ). As major decomposers in soil ecosystems, fungi are among the few organisms on the planet that can feed on chemically stable forms of organic C ( Šnajdr et al., 2011 ; Kirk & Farrell, 1987 ) but are also known to directly access recently produced plant photosynthate ( Högberg et al., 2001 ). This study improves quantification of substrate utilization by different fungal ecotypes in order to help define the rates and controls of fungal production and the cycling of soil organic matter.
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A Reappraisal of Hydrocarbons Generation and Destruction in the Petroleum Systems of Southern Aquitaine (France).
Authors R. Michels, D. Rallakis, A. Elias-Bahnan, G. Barré, J. Pironon, S. Calassou and E.C. GaucherSummarySedimentary basins in compressive settings have often complex geological histories and features. Therefore, they present a real challenge in oil and gas exploration. Recent revision of the geodynamic evolution of the North Pyrenees mountain range (France) lead to consider the effects of intense heat flow during the rifting phase prior to compression. We investigated the consequences of this previously unrecognized heating episode on the evolution of the fluids within the petroleum systems on the southern rim of the north Pyrenean foreland basin (Aquitaine basin, France). Taking into account the geodynamic frame, fluids geochemistry was investigated using fluid inclusions from major reservoirs, reservoir gas and oils geochemistry, maturation of the source-rocks through basin modelling and artificial maturation, multiple sulfur isotopes analysis. Results permit to reconsider the maturation history of source rocks, conditions and impact of TSR, secondary migration and reservoir filling as well as to understand the distribution of gas vs petroleum and sourness of fields.
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Molecular Characterization and Geochemical Significance of No Compounds in Saline Lacustrine Source Rock
More LessSummaryNO compounds refer to compounds containing N and O heteroatoms, which are widely present in geological bodies. NO compounds contain rich geological and geochemical information and they are of great significance for petroleum exploration. High-resolution mass spectrometry (FT-ICR MS) is used to analyze the composition and distribution characteristics of nitrogen and oxygen heteroatom compounds in the source rocks of saline lacustrine facies. The results show that a total of 12 types of NO heteroatom compounds were detected in the analyzed samples, including N1, N1O1, N1O2, N1O3, N1S1, N1S2, N2O1, O1, O2, O3, O3S1, O4, mainly O2 and O3, followed by N1 and N1O1; The N1 category is dominated by DBE=9, 12, 15 and 18. The distribution of O2 compounds is controlled by biogenic sources and has great potential in predicting the original parent material. N1, O2, and N1O1 compounds are all influenced by maturity with polarization performance. NO compounds are also affected by the deposition environment. It is observed that there are abundant O2 and N1O1 compounds in the saline lacustrine facies source rocks. The research results can shed light for the research of genetic mechanism of oil and gas
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Biomarker Data Demonstrate that Perturbation of the Terrestrial Methane Cycle is a Common Feature of Hyperthermals
Authors D. Naafs, A. Ebinghaus, D.W. Jolley and D.B. KempSummaryNovel biomarker data provide new insights into the impact of hyper thermals on key biogeochemical cycles. We show that the Dan-C2 hyper thermal led to a major perturbation in a terrestrial lake system, including an intensified terrestrial methane cycle. Our data for the first time confirm the hypothesis that the perturbation of the terrestrial methane cycle was a common positive feedback mechanism for hyperthermals during the Paleogene.
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Global Temperature and pH Calibrations Based on Bacterial 3-HYDROXY Fatty Acids in Soils
Authors P. Véquaud, S. Derenne, A. Thibault, C. Anquetil, G. Bonanomi, S. Collin, S. Contreras, A. Nottingham, P. Sabatier, N. Salinas, W.P. Scott, J.P. Werne and A. HuguetSummary3-hydroxy fatty acids (3-OH FA), produced by Gram-negative bacteria, were recently proposed as promising temperature and pH proxies in terrestrial settings. Nevertheless, the existing correlations between pH/temperature and indices derived from 3-OH FA distribution are based on a small soil dataset (ca. 70 samples) only applicable regionally. The aim of this study was to investigate the applicability of 3-OH FAs as mean annual air temperature (MAAT) and pH proxies at the global level using an extended dataset of 168 surficial soils from 8 globally distributed elevational transects. Strong linear relationships between 3-OH FA-derived indices and MAAT/pH could only be obtained locally, for some of the individual transects. In addition to linear regressions, non-parametric, machine learning models were used to improve the global relationships between 3-OH FA distribution and MAAT/pH. Strong global correlations between MAAT/pH and 3-OH FA relative abundances were obtained by using multiple linear regression, k-NN and random forest models.
The applicability of the k-NN and random forest models for paleotemperature reconstruction was tested with the MAAT record from a Chinese speleothem. The calibration based on the random forest model appeared to be the most robust. These results demonstrate the potential of 3-OH FAs as paleoproxies in terrestrial settings.
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EVALUATION OF ERODED MESOZOIC FORMATIONS IN NORTHERN ALSACE (FRANCE) USING ORGANIC GEOCHEMISTRY AND BASIN THERMAL MODELLING
Authors L. Tchang-tchong, P. Faure-Catteloin, E. Gaucher, C. Lorgeoux and R. MichelsSummaryIn the URG, the terminal Jurassic and Cretaceous formations are missing. It remains uncertain whether their absence is related to a sedimentary hiatus or a period of erosion. The geochemical analyses of the Jurassic outcrops of Pechelbronn area show that the Mesozoic formations are immature. It suggests that these deposits were not sufficiently buried before the Cretaceous. By using molecular markers, vitrinite reflectance, kinetic properties of source rocks, artificial maturation and 1D thermal basin models, we can estimate a maximum paleo-burial, evaluate the heat flux and simulate the oil generation.
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HYDROCARBON MASS BALANCE CALCULATIONS IN PETROLEUM SYSTEMS EXPERIENCING THERMOCHEMICAL SULFATE REDUCTION (TSR)
Authors D. Rallakis, R. Michels, A. Elias-Bahnan, G. Barré, J. Pironon, C. Lorgeoux, S. Calassou and E.C. GaucherSummaryThe quantitative assessment of thermochemical sulfate reduction (TSR) in petroleum systems is to date not entirely understood. Since the term TSR was first established in the 1970’s, many equations have been proposed to explain the kinetics of the reaction. Each reaction returns very often different numerical results, which reveals the degree of uncertainty. The area of study is located in SW France, in the South Aquitaine Basin where the giant sour dry gas (up to 18 vol% H2S) field of Lacq is located. The present study evaluates three TSR net equations taken from literature ( Orr, 1974 ; Goldhaber and Orr, 1995 ; Worden et al., 1995 ; Machel, 2001 ; Mougin et al., 2007 ; Liu et al., 2013 ) by applying them to mass balance calculations on the Lacq petroleum system. Objective is to compare constency of the calculated masss balance with the geological situation of the system.
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Investigating water depth influence on organic paleotemperature proxies from sedimentary archives
Authors D. Varma, K. Hättig, M. Van der Meer, G. Reichart and S. SchoutenSummaryThe TEX₈₆ has been widely used as a paleothermometer to reconstruct past water temperatures. A recent study had suggested a re-calibration of TEX₈₆ to deep sub-surface ocean temperatures, far deeper than previously assumed for TEX₈₆ signals. Such a calibration would imply a potential influence of water depth on TEX₈₆ values from sites with widely varying water depths. Here we investigate the potential impact of water depth on organic temperature proxies by analyzing sedimentary signals (TEX₈₆ and UK’₃₇) from two geographically proximal sites, but from different water depths, encompassing several glacial-interglacial cycles in the Late Quaternary. We observe that TEX₈₆ temperature records from nearby shallow and deep site show no significant difference and yield similar temperature estimates as the UK’₃₇.
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Evidence of Human Controlled Fires at Acheulean Site of Valdocarros Ii (Spain, Mis 8/7): Application of Organic Geochemistry
More LessSummaryIn this study, we focus on the site Valdocarros II, in the Jarama river valley (Madrid) in central Spain, despite being an open-air site, we identify anthropogenic evidence of hearts or burning by-products via a multi-proxy approach. The site of Valdocarros II (Madrid, Spain) is located in the Jarama basin with evidence of human occupancy dating to ca. 240 ka (transition of Marine Isotope Stage 8/7). The site is one of the very few Middle Pleistocene localities to have documented associations of bones and acheulean stone tools in different levels. Therefore, in this study, we examined the distribution of multiple compound classes (n-alkanes, n-alcohols, n-alkanoic acids and polycyclic aromatic hydrocarbons (PAHs) of a total of 28 samples excavated around 11 fire hearths. Moreover, samples from Hearth-1 showed the presence of 18-Norabieta-8,11,13-trie4,5 that indicate conifers wood burning, as well most samples show abundances of 2-ring, 3-ring methyl-, and di-methyl PAHs that are indicators of wood burning. Our results add to our still-limited knowledge about the controlled use of fire in the Upper Palaeolithic and contribute to ongoing debates on the behavioral complexity of the human groups with acheulean technology in Europe.
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Total Organic Carbon Evaluation of Heterogeneous Coaly Facies Using Well Logs Data, Carboniferous Lorraine Basin (France).
Authors S. Allouti, R. Michels, A. Izart, M. Mombo-Mouketo, F. Malartre, D. Bartier, Y. Géraud and F. NassifSummaryContinental fluvio-lacustrine coal bearing strata in the Carboniferous of the Saar-Lorraine basin are particularly heterogenous in their distribution. This renders source-rock volume evaluation difficult. This study focuses on the TOC determination along well-log. When cores are available, sample picking and TOC measurements through lab methods is not satisfactory since it generates discontinuous data sets. An alternative method is to use continuous well-log data and calculate TOC using DeltalogR or Carbolog methods. TOC assessment is quite accurate for sandy facies but underestimates values for coaly shales, shaly coals and coals seams. Objectives of this presentation will be to explain why TOC are underestimated for shales and coal seams, how to correct the calculated values and how this impacts the source-rock volumes estimates in these unconventional reservoirs.
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Hydrocarbon Molecular Markers in Bottom Sediments of the Focus Fluid Discharge Zones of the Lake Baikal
Authors I. Morgunova, A. Krylov, P. Semenov, V. Petrova, A. Kursheva, I. Litvinenko, S. Malyshev and O. KhlystovSummaryThe main idea of this study was to identify the background and anomaly distribution of hydrocarbon molecular markers in sediments of the lake Baikal and to define organic matter sources and specificity of its formation under the diagenetic and fluid discharge conditions. The study has shown that processes of hydrocarbon biodegradation are widespread in sediments of the oil discharge zone of the lake Baikal, but are not characteristic for the areas of mud volcanism and hydrothermal venting. The composition of hydrocarbon molecular markers in sediments near the mud volcano and hydrothermal vent area testify to the active growth of microbial biomass that uses methane and low molecular weight hydrocarbons coming from the deep as a main carbon source.
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ORGANIC POLLUTION OF SOIL CAUSED BY THE MINING INDUSTRY ON THE SOUTH OF POLAND – A CASE STUDY
Authors E.A. Szram, M.J. Fabiańska and M. KondrackaSummaryIn southern Poland, the mining industry caused diverse wastes to be produced and stored (post-mining waste, tailings from flotation, washing, and smelting). Perennial storage of industrial waste leads to pollutions of soil, surface, and underground water. Trace elements and toxic organic compounds in wastes are mobilised by surface runoff and the infiltration of rainwater into the ground. Thus the soil in the dump vicinity is contaminated. Such pollution can spread over a long distance.
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HYDROUS PYROLYSIS IN THE SIMULATION OF COAL WASTE SELF-HEATING
Authors M.J. Fabiańska, D. Więcław, M. Misz-Kennan, E.A. Szram, J. Ciesielczuk and K.J. JurekSummaryCoal wastes are produced in large amounts at various stages of coal exploitation. These rocks require special dump sites designed to store them for many years. If sufficiently large volumes of coal waste are accumulated, self-heating driven by their oxidation may occur. This process generates toxic compounds contaminating the atmosphere, water, and soil. Self-heating is a highly variable process since it depends on numerous factors. Hydropyrolysis experiments simulate well natural self-heating of coal wastes occurring in the presence of water. Pyrolysates show composition analogous to that of self-heating products what allow to predict types of contaminants formed in the process.
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Potential Water and Soil Contaminants from Coal Waste Dump Being at the Late Stage of Self-Heating (Rymer Cones, Poland)
Authors M. Lupanciuc, M.J. Fabiańska, E.A. Szram and D. WięcławSummaryCoal mining generates a great amount of wastes deposited in coal waste dumps, commonly adjacent to the mines. Its oxidation during storage in dumps often leads to self-heating or even self-ignition. This process produces large amounts of polar compounds that are relatively well water-soluble. They are leached by rainwater from permeable coal wastes, only loosely packed within a dump. The dissolving of better water-soluble compounds such as phenols, present in coal wastes, has led to their pre-concentration in leachates. Despite their relatively low stability, polar compounds were well preserved in pyrolysates formed during self-heating. Thus, even after self-heating ceasing, cold coal wastes surrounding overburnt zones can still be a source of water and soil contaminants. Phenols and aromatic acids can be considered as markers of coal waste contamination.
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Determination of Methane Cracking in Pyrolysis Experiment and its Geochemical Significance
More LessSummaryThe methane will be cracked in a certain thermal maturity stage, but it is uncertain if the methane of shale gas at high-over maturity has been cracked. In the present work, methane pyrolysis experiments were carried out in closed gold-tube system to investigate methane cracking and its carbon isotope fractionation.
From the pyrolysates, we detected the cracking of CH4 and the generation of bigger hydrocarbons like C2H4, C2H6, and C3H8 from the methane pyrolysis experiments within the shale gas maturity scope. CH4 cracking and recombined to C2H6 will cause the residual CH4 enriched whereas the produced C2H6 depleted in 13C, however, the secondary reaction of C2H6 will complicate the isotope distribution features of the pyrolysates in the methane pyrolysis experiments.
Based on our experimental results and the data of the shale gas reservoirs from different regions of the world, we suggested that CH4 will be cracked and combined into C2H6 in high-over matured shales. When the contribution from methane-derived C2H6 is sufficiently massive, the commonly found order of δ13Cmethane < δ13Cethane will change with increasing maturity (e.g. vitrinite reflectance, Ro > ∼2.0%) and a carbon isotope reversal will occur for the shale gas.
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POTENTIAL THERMAL MATURITY PARAMETERS ASSOCIATED WITH AROMATIC HYDROCARBONS IN LIGHT CRUDE OILS
More LessSummaryIn this work, we found that some conventional maturity parameters such as Ts/(Ts+Tm), C29-20S/(20S+20R), and C29-sterane-ββ/(αα+ββ) have reached an equilibrium value without changes after the high maturity stage (such as Ro%>1.3), or breakdown and no longer applicable, and thus cannot be used to properly evaluate the thermal evolution stage of crude oil reservoirs. But the results from this present work showed that toluene (Tol) and methy cyclohexane (MCH) maybe had an inherited relationship in the oil and then the ratio of Tol/(MCH+Tol) can be applied to evaluate the thermal stage of oil reservoirs( Cheng et al,.2018 ). Furthermore 2-methy naphthalene (2-MN) and 1-methy naphthalene (1-MN) have different thermal stability, the ratios of 2-MN/(1-MN+2-MN) were linearly changed with the Easy%Ro.
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FACTORS CONTROLLING THE ORGANIC MATTER ACCUMULATION OF CAMBRIAN STRATA IN THE WESTERN AND EASTERN TARIM BASIN, NW CHINA
More LessSummaryLower Cambrian black shales are widely distributed in the Tarim Basin, NW China, but those in the Keping area in the west have a high total organic carbon (TOC) content different from those in the Kuluketage area in the northeast of the basin. The Cambrian Yuertusi Formation in the Shiairike section (Keping) and the Xishanbulake Formation in the Yaerdangshan section (Kuluketage) are time-equivalent and can be correlated. Black shales of the Yuertusi Formation have lower δ13CKer values (<−34‰) than the Xishanbulake Formations (δ13CKer values >−34‰). These values suggest that black shales in the Yuertusi Formation were dominated by benthic algae, whereas rocks in the Xishanbulake Formation contain substantial amounts of planktonic algae. Analyses of trace elements demonstrate an anoxic depositional environment, with high productivity in both the Yuertusi and Xishanbulake Formations. The enhanced productivity was promoted by upwelling fluids and hydrothermal events, leading to the enrichment of nutrient elements such as barium, cadmium, copper, phosphorus, nickel, vanadium, and zinc. More terrigenous inorganic detritus input to the Xishanbulake Formation, which led to less amounts of organic matter and degradation of planktonic algae during sedimentation, resulted in a lower TOC content than the Yuertusi Formation.
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ENVIRONMENTAL CONTROLS ON BACTERIAL LIPID PRODUCTION BY A METHANOTROPH-METHYLOTROPH CO-CULTURE
Authors N. Richter, S. Van Grinsven, L. Villanueva, E.C. Hopmans, N. Bale and D. RushSummaryMethane-oxidizing bacteria regulate the natural release of methane, however, the role of aerobic methane oxidation in the geologic record is poorly constrained. Our study evaluates potential biomarkers for methane-oxidizing bacteria by assessing the environmental controls on bacteriohopanepolyol (BHP) production by a Type I methanotroph, Methylobacter sp. We also evaluate the partnership of Methylobacter sp. with a methylotroph, Methylotenera, sp., which is known to co-occur with methanotrophs and is thought to play a role in enhancing methane oxidation rates. We set up incubation experiments for an enrichment co-culture of Methylobacter sp. and Methylotenera sp. to evaluate how temperature, methane concentrations, and salinity influence (1) the culture’s lipidome (specifically BHPs), (2) the community composition, and (3) methane oxidation rates.
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Natural and Anthropogenic Biomarkers in Urban Speleothems
Authors J. Jacob, A. Diacre, T. Thiebault, L. Fougère, E. Destandau, C. Le Milbeau, P. Branchu, E. Dumont and E. Pons-BranchuSummaryWe analysed biomarkers enclosed in carbonate crusts deposited in urban surrounding as tracers of pollution
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Response Of Carbon Cycling To Hydroclimate Changes In The Subtropical Carbon-rich Wetland Ecosystem During The Late Pleistocene.
By Y. YangSummaryA borehole core (ZK7) was collected in the Dajiuhu Basin, in the middle reaches of the Yangtze River. Lipid and bulk geochemical analyses were conducted to exploit the responses of past geochemical processes to hydroclimate changes. These preliminary results clearly showed a drastic shift of paleoecological processes during the transition from a lacustrine phase to a peat accumulating condition. More work is conducting to infer how is the methane dynamic during this shift.
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ORIGIN AND FATE OF ISOPRENOID GLYCEROL DIALKANOL DIETHERS IN SEDIMENTS FROM LATE MIOCENE TO MID-EOCENE
Authors D. Mitrovic, E. Hopmans, N. Bale and S. SchoutenSummaryIn the past decade especially, more light has been shed on the high diversity in structures of isoprenoid glycerol dialkyl glycerol tetraethers, providing improved insight into both their origin and fate in different settings. A closely related set of isoprenoidal lipids, isoprenoid glycerol dialkanol diethers (isoGDDs), were reported by Liu at al. (2012a ; 2012b ) in marine subsurface sediments. In this study we investigated the occurrence and distribution of GDGTs and GDDs in sediment cores from 3 well-known organic rich sampling sites, Messel oil shale, Vena del Gesso evaporites and Monterey sediments. The strong correlation in abundance and isomer distributions between isoGDDs and isoGDGTs strongly suggest that isoGDDs predominantly have a diagenetic origin, forming by glycerol cleavage of isoGDGTs. The rate at which this happens likely depends upon many factors. Further work will be carried out in order to ascertain the link between these two lipid classes.
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The Benefit of Geochemistry and Basin Modeling Integration for Oil & Gas Exploration. The Case Study for Migration Analysis
Authors I. Campoli, D. Kalacheva, N. Morozov, O. Zakharova, A. Gulyaev and F. GaynetdinovSummaryPetroleum systems analysis has been carried out to better understand migration and filling processes in the eastern edge of the West Siberian basin (Yamalo-Nenets Autonomous District, Russia). Within an area of 37 793 km2 two main petroleum kitchens for Upper – Jurassic Bazhenov formation were distinguished which generated petroleum and guaranteed oil volumes to form fields in the Upper - Jurassic section of sedimentary cover. The migration processes are dominated by downward and lateral fluid flow with filled-to-spill mechanism.
The results of this research provided understanding of the lateral limit and maximum distance for migration, which were later supported by the results of drilling of the well. Allowed to evaluate geological risks, correct exploration plans and change priorities in the list of prospects. It also helped to better understand geological reasons for fluid properties in Upper - Jurassic section and plan research of deeper section to find additional source rocks in Lower - Jurassic section which was previously never taken into account in this zone. Later this statement was proved by the results of geochemical pyrolysis analysis. The upgraiding of the model is planned in 2021 to solve more local issues for production process.
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Utilization of Ancient Petrogenic Carbon in Svalbard Sediments, Derived from Glacial Meltwater Streams
Authors M. Ruben and S. DerenneSummaryThe Study addresses the subject of ancient carbon utilization in sediments of Hornsund Fjord, Svalbard. Using a combined approach of biomarker analysis, lipidology, and compound specific radiocarbon dating. We were able to show that the local sedimentary microbes utilize "presumably recalcitrant" petrogenic organic matter for their biosynthesis to a certain extend. Indicating its degradation in the subsurface and hence displaying a not yet accounted source of fissile carbon entering today's carbon cycle.
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δ13C Compositions of Bacteriohopanetrol Isomers Reveal Bacterial Processes Involved in the Carbon Cycle
SummaryBacteria play key roles in the carbon cycle. In many sediments and peatlands, methanotrophic bacteria consume a portion of released methane, reducing the emissions of this potent greenhouse gas. In marine oxygen minimum zones (OMZ) and other anoxic settings, anaerobic ammonium oxidizing (anammox) bacteria remove bioavailable nitrogen while performing chemoautotrophic carbon fixation. Methanotrophic and anammox bacteria synthesize a wide number of complex bacteriohopanepolyols (BHPs), comprising notably several stereoisomers of bacteriohopanetetrols (BHTs), which are used as biomarker lipids. We used a gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) method to measure the δ13C of BHTs of cultured bacteria. These δ13C values were combined with bulk isotopic measurements of the bacterial biomass and δ13C analyses of the bacterial growth substrates to establish carbon isotopic fractionation from substrate to biomass to BHT lipid. We demonstrated that bacteria using different metabolic pathways produced distinct fractionation factors between substrate and BHTs, which potentially allows for distinguishing BHTs produced by ‘Ca. Brocadia’ and methanotrophs from other freshwater producers (e.g. in peatlands). Measurement of BHT-specific fractionation factors allowed us to better constrain the contribution of anammox bacteria to fixed carbon in OMZ. This work expands the application of BHT isomers to isotopically identify carbon cycle processes.
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Terrestrial Temperatures Peak in the First Millenia After the Cretaceous-Paleogene Boundary
SummaryThe Cretaceous-Paleogene (K-Pg) boundary extinction represents one of the most severe, with approximately 75% of life on earth suffering extinction. An new terrestrial mean annual air temperature (MAAT) record based on branched tetraether data from southern Saskatchewan (Canada) permits, for the first time, the recognition of a distinct episode of rapid global warming in the first approximately 1 ka of the Paleogene, which is attributed to a rapid release of CO2 at or around the K-Pg boundary. Irrespective of the source(s) of CO2, the extinction on land may therefore have been partly driven by MAATs exceeding a threshold for ecosystem resilience. These data are the first in their kind at this resolution, providing new boundary conditions of absolute values, and rates of temperature change. Further studies of terrestrial MAAT at a similar resolution will be essential for demonstrating the unparalleled trends observed in our record to be a global phenomenon.
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Fuelling Earliest Life — Volatile Organic Compounds in 3.5 GA Old Fluid Inclusions
Authors H. Mißbach, J. Duda, A.M. Van den Kerkhof, V. Lüders, A. Pack, J. Reitner and V. ThielSummaryIt is widely accepted that small organic molecules played a central role in the emergence of life on Earth. As yet, however, there has been no conclusive evidence for the existence of the discussed relevant candidate molecules on early Earth. Here we report on indigenous, biologically-relevant organic molecules in 3.5 Ga old barite-hosted fluid inclusions from the Dresser Formation in Western Australia. We characterized the organic inventories by combining fluid inclusion petrography, stable isotope analysis and different GC-MS techniques. Our study establishes a primary origin of the fluid inclusions. They contain CO2, H2S and H2O, minor amounts of COS, CS2, N2, and CH4 as well as various oxygen and/or sulfur containing organic molecules. Notably, most of the identified compounds could have served as substrate for purported ancestral sulphur and methanogenic metabolisms. Perhaps most remarkably, the fluid inclusions also contain the stable building blocks of methyl thioacetate which is a potential key-agent in the emergence of life. Thus, our study provides the first robust evidence for the existence of such organic compounds on the early Earth and strongly supports the idea that microbial life in the 3.5 Ga old Dresser Formation was linked to hydrothermal seepage.
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Long-Term Anoxia Driven by High Temperature of Equatorial Atlantic During Cenomanian Leading up to OAE 2
Authors M.A.F. Abraham, D. Naafs and R. PancostAbstractOceanic Anoxic Event (OAE) 2 occurred during the Cenomanian/Turonian and marks one of the most significant perturbations of Earth’s system of the last 250 million years. Although the burial of black shales in the marine environment under depleted (bottom) water column oxygen conditions was widespread during OAE 2, the state of anoxia in the million years leading up to OAE 2 and the correlation between anoxia and temperature are poorly constrained. Here, we report long-term biomarkers records of (a) water column anoxia, (b) water column and photic zone euxinia (PZE), and c) TEX86-based sea surface temperature (SST) from Demerara Rise (ODP Site 1258) that span the Albian to Turonian, including OAE 2. Our data suggest a depositional environment under long-term anoxic condition at Demerara Rise during the Cenomanian as indicated by elevated total organic carbon content (up to 10 wt.%) and episodic occurrence of the biomarkers lycopane and 28,30-bisnorhopane, which at present are found in the anoxic marine such as Black Sea (Wakeham et al., 1993) and Monterey Formation (Schoell et al., 1992), respectively. The extent of water column anoxia gradually intensified and peaked during OAE 2 when the presence of hopanoid thiophenes and free isorenieratane indicate euxinic conditions in the water column, at times reaching the photic zone. This long-term progression of marine de-oxygenation coincides with a gradual increase in SSTs at the site. TEX86-based SSTs indicate a long-term warming of ∼ 7 °C during the Cenomanian to maximum values of 41 °C during OAE 2. The abrupt declined in SSTs following OAE 2 during the Turonian indicates termination of long-term anoxia via re-oxygenation of water column in phase with low TOC and absence of anoxia and euxinia biomarkers. This study highlights the impact of Earth’s climate state on marine oxygenation with an increase in temperature driving the ocean’s state from hypoxia into severe anoxia and eventually euxinia, likely due to weathering feedback mechanisms related to warming and changes in the hydrological cycle.
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Changes of Biomarkers, Isotopes and Macerals of Polish Coals and Shales: Maturation Simulated by Hydrous Pyrolysis
Authors M. Kotarba, M. Słowakiewicz, K. Jurek, M. Waliczek and D. WięcławSummaryThe bitumen yields of Carboniferous coals and shales from USCB and LCB after 330oC HP are higher than in initial coals and shales and somewhat higher than of coals and shales after 360oC HP. The distribution of exsudatinite in coals is higher at 330°C and decreases at 360°C HP. Contrary to shales at 360°C HP the exsudatinite content slightly increases. This phenomenon could be caused by the presence of clay minerals in shales which have a general retention effect during hydrocarbon generation. The results of biomarker and isotope analyses reveal that bitumen is always co-genetic with corresponding kerogen in coals and shales, and their deposition was in a brakish-lacustrine environment, and the microbially reworked organic matter could be caused by: (i) contribution of planktonic or benthic algae organic matter, (ii) more anoxic conditions in sedimentation basin, which impede bacterial growth and reworking of organic matter and (iii) contribution of terrestrial organic matter was higher than in other cases, and more organic matter could preserve in primal form.
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Molecular Investigation of Archaeological Ambers from Alsace (Ne France): Origins and Alteration Processes
Authors S. Schmitt, P. Adam, P. Schaeffer, C. Féliu, N. Schneider-Schwien, D. Minni, M. Châtelet, E. Boes, D. Azar and A. NelSummaryA set of amber samples collected from archaeological burials at three different sites in Alsace (NE France) and dated back to the Bronze Age and the high Middle Age, as well as European ambers from potential geological sources have been investigated. Based on GC-MS analysis of lipid biomarkers occurring in the solvent extract and of those released by chemical degradation which comprised various diterpenoids and succinates, it appears that the archaeological samples correspond to Baltic amber, confirming that the Baltic region was a source of amber for Alsace, at least during the Bronze Age and the High Middle Age. Identification of the source of ambers using lipid distributions was possible despite alteration of the molecular signatures by natural degradation processes.
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HYDROCARBON PROPERTIES OF THE BAZHENOV FORMATION SOURCE ROCKS WITH DIFFERENT MATURITY
Authors M. Tikhonova, A. Kalmykov, O. Vidishcheva, D. Ivanova, V. Levkina, R. Borisov and G. KalmykovSummaryBazhenov formation source rocks from wells with different maturity of organic matter were investigated by sequential extraction. Hydrocarbons extracted with hexane from open pores and with chloroform from blocked pores were investigated by FID-GC and GC-MS methods. It was found that hydrocarbons composition in open and blocked pores depends not only on maturity, but also on lithological composition of rocks and migration processes. In one well not only maturation, but also sedimentary condition biomarker parameters may vary through the depth of section. Reservoirs are filled with migrated hydrocarbons, that are of higher maturity and contain higher amount of n-alkanes with shorter chains in hexane extracts. Hydrocarbons formed in continental conditions were also found in the rocks at the bottom of Bazhenov formation, formed in marine conditions, which means there was another source rock deeper than Bazhenov formation. Concentration of silica, carbonates and pyrite affect the processes of hydrocarbons generation and influence some biomarker parameters values. That is lithological and reservoir properties of the Bazhenov source rocks as well as maturity of organic matter should be analyzed for investigation of oil and gas generation and migration processes.
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The Stable Carbon Isotope Geochemistry of Natural Gas After 20 Years of Shale Gas Development
Authors J. Cesar, B. Mayer and O. H. ArdakaniSummaryThis study discusses the new perspectives on the stable carbon isotope distribution in natural gas hydrocarbons, with special focus on the evidence of a tendency to equilibrium isotope fractionation in gases from low-permeability hydrocarbon reservoirs. It also describes how the isotope equilibration expresses (or not) in the molecular composition of the produced fluids.
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STRUCTURAL INVESTIGATION OF THE MACROMOLECULAR COMPONENT OF BALTIC AMBER BY SELECTIVE CHEMICAL DEGRADATION
Authors S. Schmitt, P. Schaeffer, P. Adam, C. Féliu, N. Schneider-Schwien, D. Minni, M. Châtelet, E. Boes, D. Azar and A. NelSummaryThe constitution of Baltic amber, the role of succinic acid and, more generally, of ester bonds in the constitution of macromolecular components of amber has been further investigated by chemical degradation of the solvent insoluble part of Baltic amber using butanolysis (BuOH/HCl). Succinic acid derivatives were the sole compounds released upon butanolysis whereas other compounds which could correspond to the alcohol counterparts of succinates could not be detected by GC-MS. This result indicate that these counterparts are all located on high molecular weight structural moieties. Succinic acid thus plays a key role as cross-linking agent between oligomeric structural moieties based on diterpenoids necessarily bound by at least one non-hydrolysable C-O or C-C bond.
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New Paleoenvironmental Proxies for the Permian Irati Black Shales Based on Acidic O1 and O2 Compounds Assessed by FT-ICR-MS
SummaryVariations of the acidic polar composition of the Early Permian Irati black shales and Serra Alta shales were assessed by ESI(-) FT-ICR-MS to investigate their significance for the paleoenvironmental studies by comparison with known features in the northeastern and central-eastern Paraná Basin (Brazil). The high O>2 classes in the Serra Alta shales points to high input of terrigenous OM deposited in oxic waters. In addition, seven parameters based on O1 and O2 compounds are proposed as new paleoenvironmental proxies: phenol index (%DBE 4; O1 class); C27/C28 DBE 4 (O1 class); C27/C28 DBE 5 (O1 class); Even/OddFA; TARFA Odd (terrigenous/aquatic ratio); C36 hopanoic acid index; and hopanoic/steranoic acids ratio. Higher values of the phenol index and the TARFA indicate higher land plant input during the final black shale deposition, and higher Even/OddFA to northeastern basin samples reflects their higher content of terrigenous OM. Furthermore, variations of C27/C28 (DBE 4) and C27/C28 (DBE 5) is useful to reconstruct paleosalinity, in which higher values indicate higher salinity. The C36 hopanoic acid index is higher for the marine hypersaline basal samples from the northeastern basin, while a significant bacterial biomass signal is stored as a higher hopanoic/steranoic acids ratio for central-eastern basin samples.
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OILS OF NONMARINE GENESIS WITH AN ABNORMALLY LIGHT ISOTOPE COMPOSITION OF CARBON
Authors I. Goncharov, R. Kashapov, S. Fadeeva, A. Litvinova, A. Zherdeva, K. Kozyreva and N. OblasovSummaryThe results of the study for oils formed by organic matter of non-marine origin, which accumulated under moderately oxidizing conditions, are presented. Oils are characterized by an increased content of a light carbon isotope, which is unusual for hydrocarbons formed in such conditions.
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Carbon Isotopic Composition and Components of the Petroleum Gases from Fields in the Western Pre-Caucasus Area (Russia)
Authors I. Goncharov, N. Oblasov, M. Veklich and I. EftorSummaryThis study is about differences and similarities in the isotopic and component composition of the petroleum gases from fields in the Western Pre-Caucasus area. These gases were differentiate into three genetic types. The 1st genetic type (Akhtyrsky type) were generated by the rocks of the Middle Eocene Kuma Formation. Gases with the higher δ13C values of gas components from ethane to pentane were assigned to the 2nd (Sladkovsky) genetic type. These gases are associated with oils, the source of which was marine organic matter but the exact stratigraphic confinement of the source rock remains unclear. And the 3rd genetic type of gases (Nikolaevsky type) which the initial organic matter associated with higher terrestrial plants, which accumulated under oxidizing conditions (for oils Pr/Ph = 3.1–4.3, C27–C28–C29 steranes is 0.23–0.22–0.55). The source rock of these gases and oils remains unknown, but its age should be no younger than the Lower Cretaceous.
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OBTAINING THE KINETIC SPECTRUM OF ORGANIC MATTER AT DIFFERENT STAGES OF NATURAL THERMAL EVOLUTION
Authors R. Kashapov, I. Goncharov, N. Oblasov and V. SamoilenkoSummaryThe dependence between the Arrhenius constant and the activation energy is obtained using the results of kinetic studies of the Bazhenov formation rocks at various stages of catagenesis. Based on this dependence, a kinetic spectrum is obtained that reflects the realization of the generation potential of organic matter in the process of thermal evolution.
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Metagenomic Insight into the Metabolic Activities of Potential Btex-Degrading Populations
By M. EzeSummaryEnvironmental contamination by petroleum hydrocarbons is of concern due to the carcinogenicity and neurotoxicity of these compounds. Successful bioremediation of organic contaminants requires bacterial populations with degradative capacity for these contaminants. Through successive enrichment of microorganisms from a petroleum-contaminated soil using diesel fuel as the sole carbon and energy source, we successfully isolated a bacterial consortium that can degrade diesel fuel hydrocarbons. Metagenome analysis revealed the specific roles of different microbial populations involved in the degradation of benzene, toluene, ethylbenzene and xylene (BTEX), and the metabolic pathways involved in these reactions. One hundred and five putative coding DNA sequences (CDSs) were identified as responsible for both the activation of BTEX and central metabolism (ring-cleavage) of catechol and alkylcatechols during BTEX degradation. The majority of the CDSs were affiliated to Acidocella, which was also the dominant bacterial genus in the consortium. The inoculation of diesel fuel contaminated soils with the consortium resulted in approximately 70% hydrocarbon biodegradation, indicating the potential of the consortium for environmental remediation of petroleum hydrocarbons.
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GASEOUS POLLUTANTS GENERATED DURING DRY AND HYDROUS PYROLYSIS OF COAL WASTE: SIMULATION OF THE SELF-HEATING PROCESSES
Authors D. Więcław, K. Jurek, A. Kowalski, E. Bilkiewicz, M.J. Fabiańska, M. Misz-Kennan and J. CiesielczukSummaryPyrolysis experiments were conducted without and with water in temperatures 250, 360 and 400oC during 72 h to simulate pollutants generation from self-heating coal wastes under oxygen-depleted conditions. The molecular composition of gases generated during these experiments and their relationship with the amount of organic matter in the rock (TOC), its maturity, the temperature of the process and the influence of the water was determined. Alkanes up to C8 and alkenes to C4 were identified. The sulphur-containing compounds comprise inorganic (H2S, COS/SO2) and organic (methyl- and ethyl mercaptans, and methyl-, ethyl-, propyl- and butyl sulphides) components. The H2, CO, CO2 and N2 were recorded among the inorganic gases. The molecular composition of generated gases strongly relates to the temperature of the process. The concentration of usually increase with the increasing temperature of pyrolysis. Presence of water and elevated TOC amounts boost generation S-compounds (dominated by H2S). Presented results helped to understand and evaluate the emission of gaseous pollutants during pyrolysis of the stored coal wastes induced by self-heating. The most dangerous to the environment is the 300–400°C regime connected with the emission of elevated concentrations of hydrocarbons and S-containing compounds, especially from TOC-rich rocks.
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GEOCHEMICAL CHARACTERISTICS AND SOURCE DISCRIMINATION OF DEEP PERMIAN OILS FROM WELL XJC 1 IN THE SOUTHEASTERN JUNGGAR BASIN
Authors H.J. Zhang, S.M. Li and L. ZhangSummaryThe Junggar Basin is one of the most important superimposed basins in southeastern China, characterized by multiple source rocks and hydrocarbons productive horizons. Well XJC1 is one of the recently drilled wells with deep commercial tight oil/gas (>4000m) discovered in the Perman Lucaogou Formation (P2l) in the southeast of the basin, which suggests a great petroleum potential in this relatively low-level exploration area. Oil-oil and Oil-source rock correlation showed that the P2l oil from the XJCJ well were sourced from the P2l argillutite, which have a high hydrocarbons generation potential with large scale and a relatively wide range of thermal maturity (low to high level). It suggests a great petroleum exploration potential about normal and unconventional hydrocarbon resources in the southeastern Junggar Basin. This study would be helpful for the further petroleum exploration and exploitation in the area.
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Cyanobacterial Aromatic Carotenoids
Authors R. Summons, F. Husain, X. Cui, S. Rohret, X. Liu, P. Welander, G. Shen and D. BryantSummaryContrary to common perceptions, cyanobacteria can be the source of aromatic carotenoids preserved in sediments. Their distribution patterns differ, somewhat, from those produced by the phototrophic sulfur bacteria and are distinguished by the presence of C38 and C39 compounds which are diagenetic products of mono- and dicarboxylic acid precursors. Cyanobacterial aromatic carotenoids are most in evidence in samples from lacustrine environments and their existence likely explains some of the carbon isotopic variability of carotenoid assemblages previously thought to be derived from Chlorobi.
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Application of Biomarkers and Compound Specific Sulfur Isotope in Oil-Source Rock Correlation in the Wenliu Oilfield, Bohai Bay Basin
More LessSummaryDongpu Depression is an important petroliferous depressions in the Bohai Bay Basin, eastern China, which is a typical saline lacustrine depression. Wenliu Oilfield is the biggest oilfield in the depression. There is still some controversy about the oil source for the Wenliu oilfield. The dispute is focused on the location (in-situ or the adjacent Qianliyuan Sag) and the horizons (the Es3M or the Es3L-Es4u) of the key source rocks. Quite a few geologists suggested that the Es3M in-situ should be the most important source rocks, which is primarily dark shales with great hydrocarbon generation potential. To help unravel the origin and source rocks of the Wenliu oils, a total of 44 rock samples and 66 oil samples were collected for study by conventional geochemical methods combined with compound specific carbon/sulfur isotopic analysis. We suggested that the Wenliu Oils are mixed sources derived from both the Es3M and the Es3L-Es4U strata, and the latter should be responsible for the majority of the crude oils in the Wenliu Oifleld based on oil-oil and oil-source correlation as well as semi-quantitative comparison of biomarkers abundances. The results would be instructive for further petroleum exploration and petroleum resource evaluation in the area.
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Study of Favorable Conditions for Shale Oil and Gas Formation in Nenjiang Formation in South-Eastern Uplift Area of Songliao Basin
More LessSummaryRecently, three wells have all produced over 10m³ oil per day, which are deployed in the Cretaceous shale horizons in the Songliao Basin, indicating great potential for unconventional shale oil in that area. Great progress has been made in understanding the formation mechanisms of oil shale in the basin in terms of petrography, minerals, and sedimentary facies. However, comparatively little research has been carried out on the rock types of the provenance, which is significantly enriched in organic matter, and their influence on the shale. To assist in unravelling its geochemical characteristics and formation mechanisms, 21 rock samples were selected from the late Cretaceous Nenjiang Formation (K2n) in the southeastern uplift of the basin for analysis. The K2n dark mud shale was formed in a brackish, strongly reducing, algae enriched sedimentary environment. The lacustrine paleo-environment had high productivity and a large sedimentation rate, which was conducive to the generation and preservation of organic matter. The input of large amounts of iron, magnesium, and calcium materials to the provenance promoted the formation of oil shale. The source rock contains high levels of transition metals, which played a significant role in catalysing the evolution of kerogen and thus in hydrocarbon generation.
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A comparison of hydrocarbon loss between pyrolysis S1 and crude oils: A case study of Qingshankou shale-oil system, Songliao Basin
More LessSummaryIt is well known that oil content ( pyrolysis S1 or soluble EOM ) in a shale is under-estimated due to light hydrocarbon loss during measurement procedure, and the restoration of such loss is a great challenge while estimating shale oil resources and determining mobility. In this paper, the light hydrocarbon losses of fresh shale cores from Qingshankou Formation of northern Songliao Basin and their produced oils were compared. The results show that under ambient conditions, the hydrocarbon losses of pyrolysis S1 and crude oils overall increase with shale maturity (Ro) and oil API gravity. However, a shale with greater maturity (e.g. Ro>1.6%) tends to have better seal capacity and the hydrocarbon loss may be much lower than expected. Compared with their produced oils, shales tend to lose more light hydrocarbons. The cause of such difference is that S1 yields of a shale are composed of more light hydrocarbons and less heavy ends as indicated by gas chromatography analysis. It is suggested that restoring light hydrocarbon loss based only on oil density as proposed by previous studies will significantly under-estimated shale oil resources and more controlling factors should be considered.
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Diversity of Nitrogen-Containing Bacteriohopanepolyols: Biomarkers for Aerobic Methane Oxidation in Terrestrial CH4 Seeps
SummaryThe greenhouse gas CH4 plays an important role in the Earth’s carbon cycle as it actively influences climate change. The aerobic oxidation of CH4 (AMO) plays a key role in oxidizing CH4 before it reaches the atmosphere. AMO can be traced using different lipid biomarkers, specifically bacteriohopanepolyols (BHPs) with nitrogen-containing side chains such as aminotetrol or aminopentol. Soils are one of the largest microbial sinks for atmospheric CH4 but, to date, they have only been investigated for soil-specific BHPs and not AMO-characteristic BHPs. In this study, a new UHPLC-HRMS2 method was applied to investigate the diversity of non-derivatized BHPs in soils near two continuous terrestrial CH4 seeps in Sicily, Italy. The microbial diversity of methanotrophic bacteria was assessed by 16S rRNA gene amplicon sequencing. Overall, our data suggest that AMO-specific BHPs (e.g. aminopentol) in tandem with novel identified composite BHPs such as BHPs with an ethenolamine head group and acylated aminotriol BHPs reveal consistent trends with AMO activity in sampling transects from high to low CH4 availability. Their abundance relatively to common soil-BHPs like adenosylhopanes may potentially be used to reconstruct recent and paleomethanotrophy in terrestrial environments.
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Identification of methyl-branched alkenones with up to five double bonds in saline lakes
More LessSummaryWe demonstrate new C38 and C39 found in Lake Van and Lake Fryxell are methyl-branched alkenones (brC38Me and brC39Et). Previous assignments of these compounds as straight chain C38Me and C39Et were incorrect. Double bond positions, determined based on mass spectra of corresponding DMDS adducts, are Δ 4, Δ 7, Δ 14, Δ 21 and Δ 28 for penta-unsaturated branched alkenones. Based on published DNA data and changes of branched alkenone percentages of Lake Van, we hypothesize that branched alkenones function as storage of energy and are produced by a yet unknown species of Isochrysidales. UKbr38Me based on brC38Me alkenones has a similar trend with UK37 in the past 270 ka of Lake Van, suggesting the high temperature sensitivity of branched alkenones, same as other straight chain alkenones. Such proxies based on branched alkenones might be more reliable than UK37 and UK'37 to provide temperature record in sites with mixed alkenone productions.
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Marine fungi and the biological carbon pump - a quest for novel biomarkers for key players in the carbon cycle
Authors E. Cooper, S. Thomas, S. Ussher, D. Rush, M. Cunliffe and S. LenggerSummaryThis PhD project will study the lipidome of marine fungi in order to find lipid biomarkers that can help deduce the role marine fungi play in the marine biological carbon pump. This will be done by growing marine fungi under different nutrient regimes that mimic natural variations in the ocean.
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Organic Geochemical Characterization of Lower Cretaceous Sediments from the Sw Barents Sea
Authors E. Krasnova, A. Suslova and T. KolesnikovaSummaryThe Norwegian Barents Sea is a prolific hydrocarbon province on the Norwegian Continental Shelf (NCS) and is a key region for reconstructing the Early Cretaceous geological history of the Barents Sea region. This study presents a brief overview of the generative potential (TOC & Rock-Eval), thermal maturity and geochemical signature (Isotopes (SARA fractions), Gas-Chromatography/mass spectrometry) of Lower Cretaceous source rocks.
The samples from the SW Barents Sea show variation in thermal maturity ranging from immature to mid-mature. The data set exhibits high variability in primary organic matter precursors and hydrocarbon generation potential, which implies heterogeneous organic facies.
All samples suggest a mixture of terrestrial and marine organic matter deposited under varying redox depositional environments. Likewise, secondary processes such as thermal maturity and contamination may hamper interpretation of the original organic matter precursors.
It can be concluded that the source rock potential of the analyzed Lower Cretaceous samples is of minor importance. Our interpretation, in general, agrees with that of Bjorøy & Hall (1983) who reached a similar conclusion concerning North Sea Cretaceous rocks and in the Lower Cretaceous Kolje and Rurikfjellet formations ( Abay et al, 2018 ).
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THE POTENTIAL OF BIOMARKERS TO DISTINGUISH LOWER AND MIDDLE MIOCENE LIGNITES FROM THE COAL-MINING DISTRICT OF LUSATIA
Authors I. Kojic, J. Kus, D. Zivotic and K. StojanovicSummaryThe organic geochemical study of Lower and Middle Miocene lignites from the coal-mining district of Lusatia in eastern Germany has been performed. Since the samples showed a uniform and low degree of maturity (0.32–0.37 %Rr), it can be considered that maturity has no significant impact on biomarker distributions. Therefore, the objective of the study is to examine the potential of biomarkers to distinguish Lower and Middle Miocene lignites in relation to sources and depositional environment of organic matter (OM). The biomarker patterns show relatively similar compositions in studied lignites, indicating no significant change in palaeclimate from Lower to Middle Miocene. Middle Miocene lignites are characterized by more pronounced variations of biomarker signatures due to the more pronounced fluctuation of water-level and/or palaeo-wildfires. Peatification was performed under stable water-level. The main differences between Middle and Lower Miocene coals are expressed by higher dehydroicetexane content, Paq index, the tetracyclic/tricyclic diterpanes ratio and non-hopanoid triterpenoids content, as well as by lower content of hopenes and fernenes in the latter one. Mentioned results indicate decreasing contribution of Cupressaceae and emergent macrophytes, associated with increased input of Pinaceae, angiosperms and ferns to the precursor OM of Middle Miocene samples in comparison to Lower Miocene samples.
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HYDROLOGICAL AND BIOGEOCHEMICAL CYCLING DURING RAPID WARMING EVENTS IN THE CONTINENTAL INTERIOR UNITED STATES
Authors A. Elson, M. Rohrssen, J. Marshall, G. Inglis and J. WhitesideSummaryThe Green River Formation of the western US represents a ∼15 million-year record of unusually large, productive Eocene lakes. The development of a particularly organic-rich (up to 43% total organic content) Mahogany oil shale (49.3 to 48.7 Ma) occurred at a key climate transition and during the decline of the Early Eocene Climatic Optimum (EECO).
Hydrogen isotopic compositions (δ2H) of leaf wax (n-alkanes) and algal (phytane) lipids preserved in the Mahogany Zone are used to reconstruct precipitation and lake water δ2H, respectively. Algal lipid and leaf wax δ2H values exhibit a strong linear relationship (R2 = 0.8), suggesting that algae and higher plants are utilising the same hydrogen-bearing sources for biosynthesis (i.e. lake water δ2H).
δ2H in n-alkanes and phytane become increasingly depleted upward through the Mahogany Zone, indicating increased precipitation during the demise of the EECO. Similarly, biomarker trends differ from those expected during a lacustrine drying-up cycle, revealing a continental-interior hydrological response to cooling.
Results of algal lipid and leaf wax δ2H, with additional lipid and terrestrial biomarker profiles and petrographic data, allow hydrological change to be differentiated from broader ecosystem change during the EECO.
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Species mixing in alkenone producers brings new opportunities in paleoclimate and paleoceanographic reconstruction
More LessSummaryAlkenones are a type of ketones produced by a certain order of algae. Its unsaturation degree has been widely applied as a sea surface temperature proxy. Our studies focus on differentiating alkenone producing species, which can reveal information about paleo sea ice and sea surface salinity.
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Biomarkers from Fossilised Hot Spring Sinters: Implications for the Search for Life on Mars
Authors S. George, B. Teece, J. Hartz, T. Djokic, S. Ruff, O. Alard, K. Campbell and M. Van KranendonkSummaryThe search for life on Mars has been guided in part by the search for biosignatures in Martian analogues on Earth. Siliceous hot springs are key astrobiological targets as they provide ideal conditions for biogenesis. This work documents biomarker analyses carried out on siliceous hot spring sinters from El Tatio, Chile, and from the Taupo Volcanic Zone, New Zealand, with an age range from actively forming to fossil deposits (∼1–21 ka). In addition, older samples (Pliocene–Miocene) were analysed from the Coromandel Volcanic Zone, New Zealand. Some of the data have already been published. The key hydrocarbons detected in some (or all) of the samples include n-alkanes, isoprenoids, monomethylalkanes, tricyclic and tetracyclic terpanes, hopanes, 2α-methylhopanes, steranes, and some aromatic hydrocarbons. A series of biomarker and aromatic hydrocarbon maturity parameters suggest that most samples have entered the oil generation window, and that maturity is strongly variable between samples and by parameter. These signals are indicative of organic matter sourced from subsurface hydrothermal fluids migrating from deeper immature source rocks that have been hydrothermally altered, rather than from the in situ material preserved within the samples in the hot spring environment.
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THERMOGENIC GAS HYDRATES IN SOUTH CHINA SEA: EVIDENCE FROM HYDRATE-BEARING SEDIMENT RELEASED VOLATILE MOLECULAR MARKERS
More LessSummaryThe volatile components released from hydrate-bearing sediment collected in South China Sea via home-made apparatus comprise high abundance of diamondoids and show high stage of molecular maturity parameters, implying that they should be mainly derived from the mature to postmature source rock beds in the QND Basin. This supports that thermogenic gas does significantly contribute the gas hydrate in this area.
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Laboratory Modeling of Organic Matter Maturation in Bazhenov Source Rocks: Hydrocarbons Composition Variation in Time
Authors A. Kalmykov, M. Tikhonova, V. Levkina, D. Ivanova, G. Savostin, G. Kalmykov and A. BychkovSummaryThe abstract represents the results of pyrolysis and GC-MS investigations of step-by-step laboratory modeling of organic matter maturation in Bazhenov formation rocks. Two rock samples with immature kerogen were heated in autoclaves under 300°C and 30 MPa, with sampling of liquid products and rock pieces each 12 h. The results have shown that pyrolysis parameters TOC, S2 and HI decreased exponentially, simulating all steps of kerogen maturation, and hydrogen index reached 70 mg HC/g TOC in 7–8 days, representing the kerogen achieve end of oil window. N-alkanes were generated only during first 5–8 days depending on the sample, with predomination of n-alkanes with odd number of carbon atoms after 3–5 days. Biomarker parameters that characterize both maturity and deposition conditions change during kerogen cracking, which means kerogen not only become more mature, but have complicated structure and consists of algae and marine organisms. Patterns for hydrocarbons generation depending on different nature of kerogen were determined. Further studies on larger amount of Bazhenov samples are necessary, but obtained results allow to investigate kinetics of kerogen cracking and specified compounds production.
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Integrated Approach to the Determination of the Origin of Hydrogen Sulfide in the Oil Field (Russia)
Authors D. Kalacheva, N. Morozov, D. Abramov, M. Kremenetskiy, E. Kazak and E. AblyaSummaryDue to its high reactivity and toxicity, hydrogen sulfide is an undesirable component of oil associated gas, since it reduces its economic value and shortens the service life of technological equipment. In this paper we consider the main results of integrated geological, geochemical and hydrodynamical studies for determination of the causes of the origin and mechanisms of hydrogen sulfide formation in the composition of oil associated gas from the Y reservoir of the oil field in the Volga-Ural oil and gas basin. The research is focused on creating a quantitative model for predicting the generation of hydrogen sulfide depending on the technological parameters of the field development.
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Alteration of Soil Organic Matter Composition After 130 Years of Afforestation Assessed by Molecular Markers
Authors T.C. Speckert and G.L.B. WiesenbergSummaryAfforestation reduces carbon emissions through increased soil organic matter (SOM) stocks as well as long-term carbon sequestration. However, little is known about the alterations in the composition of organic matter (OM) after afforestation, specifically on a molecular level. The analysis of plant- and microorganism-derived molecular proxies in soil allows to trace different sources of OM and its transformation once incorporated into soil. However, focusing only on one compound class may result in flawed or incomplete conclusions due to missing information offered by other compound classes. One approach to a more reliable conclusion on the SOM dynamics is the combination of multiple compound classes.
The objective of this project is to identify the major source of SOM in a subalpine afforestation sequence (40–130 years) with Norway spruce (Picea abies L.) on a former pasture in Jaun, Switzerland with the combination of multiple plant- and microorganism-derived molecular proxies. Within this project we expect a decline in SOC stocks after 50 years (72.2 t ha-1) and a recovering after 130 years (116.8 t ha-1) of afforestation. Overall, we expect an increase in SOM, a decline in SOM quality and a higher fungal PLFA content in older forests.
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INFLUENCE OF MARINE INCURSIONS ON SOURCE ROCKS IN A SALINIZED LACUSTRINE BASIN IN THE PALEOGENE EASTERN CHINA
More LessSummaryMarine incursion is one of the possible mechanisms for the salinization of lacustrine basins, especially in the Paleogene eastern China. However, the influence of marine incursions on source rocks in salinized lacustrine basins is challenging and controversial. Here, we examine this issue using a case of the Paleogene Biyang Depression (BD) eastern China, addressing organic matter (OM) accumulation and unconventional hydrocarbon potential. Our data suggests that marine incursions have positive influence on both OM accumulation and unconventional hydrocarbon potential of source rocks in salinized lacustrine basin. However, further study on influence of different degrees (e.g., landward distance, overall water depth, and seawater-freshwater mixing) of marine incursions on source rocks in salinized lacustrine basins are still needed, especially during sea-level fluctuations.
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Elucidation of the Biosynthetic Pathway of Butanetriol Dialkyl Glycerol Tetraethers Reveals a Novel Energy-Saving Adaptation
Authors S. Coffinet, L. Mühlena, J. Lipp, C. Neubauer and K. HinrichsSummaryButanetriol dialkyl glycerol tetraethers (BDGTs) are a novel class of archaeal membrane lipids possibly related to methanogenesis. Their structure deviates from the other archaeal lipid structures, such as the glycerol dialkyl glycerol tetraethers (GDGTs), as they possess a four-carbon backbone instead of the universal glycerol moiety. Here, we combined compound-specific stable isotope probing and high-resolution mass spectrometry to investigate the biosynthetic pathway of BDGTs. We demonstrated that BDGTs result from a post-synthesis methylation of GDGTs. We further observed that biosynthesis of BDGTs was stimulated by energy and/or nutrient depletion both in vitro and in the environment. We hence posit that production of BDGTs act as an adaptation strategy to survive in energy or nutrient deprived environments such as in the deep sub-seafloor.
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IDENTIFYING CONTROLS ON ORGANIC MATTER ENRICHMENTS IN HEMIPELAGIC SETTINGS: A BIOMARKER APPROACH
Authors A. Riboulleau, M. Quijada, A. Caillaud, J. Reynaud, J. Ferry, F. Baudin and N. TribovillardSummaryThe biomarker content of several dark coloured and/or organic-rich levels from the Marnes Bleues Formation (Aptian-Albian) from the Vocontian Basin (South-eastern France) was analysed in order to compare the modes of formation of such deposits in a hemipelagic, basinal setting. The studied levels include the Goguel and Paquier Levels, deposited during oceanic anoxic events (OAE) 1a and 1b, respectively. Unexpectedly, most studied samples show comparable biomarker contents, regardless of their richness in organic matter. The data indicates an organic matter of marine algal origin, deposited under oxygenated conditions. The Paquier level, however, shows an abundance of archaea-derived biomarkers and of organo-sulfur compounds in the extract, indicating deposition under reducing conditions. The Paquier level excepted, the biomarker content indicates that depositional conditions remained overall stable during deposition of the Marnes Bleues formation, including during OAE1a. Nevertheless variations of the relative proportions of steranes, hopanes, terrestrial plant biomarkers and fire-derived polyaromatic hydrocarbons, suggest that minor environmental changes occurred and occasionally favoured organic matter enrichment in the sediment. In the end, no unique mechanism explaining the deposition of these dark coloured and/or organic-rich levels can be identified.
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LARGE REGIONAL GLACIAL-INTERGLACIAL CHANGES IN HYDROGEN ISOTOPIC COMPOSITION OF ALKENONES NEAR THE CHILEAN MARGIN
Authors K. Haettig, D. Varma, S. Schouten and M.T.J. Van der MeerSummaryPaleosalinity is an important oceanographic parameter which cannot be reconstructed with reasonable accuracy based on sedimentary records yet. Sea water isotopes correlate with salinity and are incorporated by organisms e.g. in a calcitic shell or organic material. Published down-core reconstructions of salinity from hydrogen isotope ratios of alkenones are promising but show different sensitivities regionally.
Here we present a new hydrogen isotope ratio record of long-chain alkenones (δ2HC37 ratio) in combination with oxygen isotopes of foraminifera (δ18OForaminifera) from the same samples, from the Chilean margin (ODP site 1235). We observed a decrease in both δ2HC37 and δ18OForaminifera during the last deglaciation (from 20–0 ka) and detected hydrogen isotope enrichment before the last glaciation (∼100–30 ka). Weiss et al. (2019) observed similar shifts in δ2HC37 of >20‰ and in the δ18OForaminifera in the same time frame, suggesting a consistent regional pattern.
The δ2HC37 ratios suggest salinity changes of >2 psu between now and the Last Glacial Maximum, larger than assumed ( Adkins 2002 ; Broecker, 2002 ). Further analysis of both hydrogen and oxygen isotopes of both cores combined with paleo seasurfacetemperature will help to determine why the salinity shift reconstructed based on hydrogen isotopes does not match with other proxies or models.
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Differences in δ13C Values of Levoglucosan from Lignite and Biomass Low-Temperature Combustion
Authors M. Rybicki, L. Marynowski, A. Bechtel and B.R.T. SimoneitSummaryWe showed that stable carbon levoglucosan-specific isotope analysis may be one possible way to determine the relative contributions from coal combustion versus biomass burning sources. PM samples were collected from low-temperature burning/smoldering of Miocene lignites from Poland and basket willow (Salix viminalis L.) representative of biomass.
The calculated levoglucosan δ13C values of xylites varied from −23.6 to−21.6‰, while for detritic coal samples they ranged from −24.2 to −23.1‰, with means of −22.7 and −23.7‰, respectively. The calculated levoglucosan δ13C value of baske twillow wood was−27.1‰. Values of willow wood mixtures with xylite varied from−25.8 to−23.4‰ (with an increasing proportion of xylite), while values of mixtures of willow and detritic coal ranged from−26.9 to−24.6‰ (with an increasing proportion of detritic coal). The hopanoid distributions characteristic for low-temperature lignite/peat burning, with a predominance of 22R-α,β-homohopane, ββ-hopanes and hopenes, as well as low or very low values of the homohopane index, were observed in smoke PM from most lignite samples and absent in the basket willow sample. Thus, the relatively high content of hopanes (with the occurrence of 22R-α,β-homohopane, ββ-hopanes and hopenes) in atmospheric PM samples can be treated as additional tracers of lignite combustion.
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CONTROLLED DRILL BIT METAMORPHISM (DBM) USING INDOOR RIG FLOOR EXPERIMENTS
Authors D. Strapoc, D. Gonzalez and L. GerbaudSummaryFirst time controlled drill bit metamorphism experiments using one-of-a-kind laboratory in Pau, southern France, with indoor rig floor with full capacity of controlling drilling conditions and with a closed drilling fluid loop, allowing extraction, analysis and sampling of the mud gas while-drilling, showing alkanes and alkenes being generated, as drilling conditions create more heat. Stepwise increase of WOB or RPM is followed by likewise increase in generated DBM-gases via base oil cracking at the bit cutter-rock interface.
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