Fossil Organic Matter Research Articles

A robust, agnostic molecular biosignature based on machine learning

The search for definitive biosignatures-unambiguous markers of past or present life-is a central goal of paleobiology and astrobiology. We used pyrolysis-gas chromatography coupled to mass spectrometry to analyze chemically disparate samples, including living cells, geologically processed fossil organic material, carbon-rich meteorites, and laboratory-synthesized organic compounds and mixtures. Data from each sample were employed as training and test subsets for machine-learning methods, which resulted in a model that can identify the biogenicity of both contemporary and ancient geologically processed samples with ~90% accuracy. These machine-learning methods do not rely on precise compound identification: Rather, the relational aspects of chromatographic and mass peaks provide the needed information, which underscores this method's utility for detecting alien biology.

Geochemical features of organic matter in the Lower Cretaceous deposits of the Ozhoginskaya Suite (Indigiro-Zyryansky basin)

Limited available data on molecular geochemistry indicate the predominance of terragenous organic matter in the source material of the Lower Cretaceous deposits of the Ozhoginskaya suite, which allows it to be considered gasgenerating. However, based on the mixed nature of the source material, this suite could possess potential for liquid hydrocarbon generation. The geochemical features of the organic matter were studied using classical bituminology, Fourier transform infrared spectroscopy, gas chromatography, and mass spectrometry. The results showed a regular distribution of alkanes with a predominance of low-molecular-weight homologues with a maximum at nC15-19 and low values of ∑n.c.-nC20/∑nC21-c.c., vanadylporphyrin complexes. Thus, the contribution of algal material could be significant to the composition of the fossil organic matter of the Lower Cretaceous Ozhoginsky suite with different ratios of terrigenous and aquatic components in the section. Our results on the Ozhoginskaya suite showed the similarity of geochemical parameters with the Upper Bastakh suite of the Upper Jurassic, the features of bitumoid composition, which were mainly due to the predominance of planktonic-algal material capable of generating a large amount of liquid hydrocarbons. This established similarity raises the estimate of the oil generation potential of the organic matter of the Lower Cretaceous deposits of the Ozhoginskaya suite, along with the high gas generation potential inherent in terragenous organic matter.

Paleoenvironments represented by the sediments of the Early Pliocene Mursi Formation, Omo Valley, Ethiopia

While our understanding of human origins has been enriched by extensive efforts to reconstruct the ancient environmental context of early hominins using information from hominin-bearing localities, comparatively little effort has been focused on contemporaneous fossil localities with abundant vertebrate fossils, but lacking hominins. We report here on new paleoenvironmental reconstructions of the Mursi Formation, Ethiopia, from which strata dated to >4 Ma preserve an abundant vertebrate fossil record lacking any known hominins, despite being part of a contiguous sedimentary basin known for its rich hominin fossil record. We combine new stratigraphic and sedimentological observations with data from paleosols preserved in the sedimentary sequence, along with isotopic data from pedogenic carbonate, paleosol organic matter, and sulfur minerals preserved in the sediments (gypsum, native sulfur). Paleosol features and carbon isotopic composition of fossil organic matter and pedogenic carbonate complement data from the mammalian fauna, the sum of which provide evidence of closed woodland to forest vegetation. Sedimentological data indicate that these wooded terrestrial habitats occurred near aquatic settings characterized by stagnant shallow waters of a freshwater lake, providing a reconstruction of unique habitats in contrast with hominin localities >4 Ma.

Anthropogenically driven changes to organic matter input in sediments of Lake Chaohu, Eastern China, over the past 166 years

Characterizing how and to what extent human activities have influenced organic matter (OM) input in lake sediments is essential for a thorough study of the carbon cycle and carbon burial in lake systems, but this issue has not yet been addressed. Here, the source and composition of OM in sediments of Lake Chaohu, Eastern China, over the past 166 years, were determined by analyzing stratigraphic variations in aliphatic hydrocarbons and OM pyrolysis parameters in a dated sediment core. These data, coupled with documental records, were further used to elucidate the pattern and controlling factors of OM input in the sediments. The lowest hydrogen index (HI), lowest long-chain n-alkane concentrations, and highest Paq (proxy of aquatic macrophyte input) in sediments prior to ca. 1956 indicate a minimal input of OM from phytoplankton and terrestrial plants and a larger input from submerged macrophytes. This may represent the features of OM input in primitive conditions given the mild human activities around the lake before the 1950s. In sediments from ca. 1962 to 1985, elevated HI and C17/C16n-alkane ratios indicate a greater input from phytoplankton, while the high abundances of long-chain n-alkanes and αβ-hopanes reflect an anomalously high input from terrestrial plant and fossil OM. These variations might have been caused by the rapid development of agriculture during this period, which accelerated catchment erosion and petroleum contamination and promoted the transport of allochthonous OM and nutrients to the lake. The lowest Paq in sediments during this period indicates reduced input from submerged macrophytes, probably resulting from a dam installation that modified the water to an unfavorable plant depth. In sediments after ca. 1989, the highest values of HI, short-chain n-alkane abundances, and C17/C16n-alkane ratios indicate a further increase in OM input from phytoplankton, a response to domestic and industrial discharge and subsequent lake eutrophication.

Carbon and nitrogen sequestration during primary succession in granodiorite quarries

AbstractStudies assessing the potential of mining areas for carbon sequestration focused mainly on areas after the extraction of energy raw materials, especially coal or oil shale, but little attention was paid to stone quarries and quarries of other non‐energy raw materials. We investigated carbon and nitrogen pools (stocks) along a chronosequence in the organic horizon and to a depth of 20 cm of the mineral soil in granodiorite quarries. We compared these pools and sequestration rates with other mining sites. The advantage of this study is that several differently aged quarries in a small area have the same rock chemistry and climate. Thus, the rate of pedogenesis is purely a function of time and vegetation. It is not affected by fossil organic matter or organic matter and nutrients in the topsoil used for reclamation. The vegetation succession tends towards tree cover dominated by Pine (Pinus sylvestris), Birch (Betula pendula), Willow (Salix caprea), Aspen (Populus tremula) and Alder (Alnus glutinosa). Analysis of soils from granodiorite quarries showed a natural accumulation of carbon and nitrogen in the soil to a depth of 20 cm during about 60 years of natural succession. The total soil organic carbon and nitrogen pools to a 20 cm depth average of 2482.4 g C m−2 and 179.1 g N m−2, respectively, in the oldest plots >50 years old. These values are for carbon 2.6 and nitrogen 2.4 times lower compared to pools in the same depth on control plots. Carbon and nitrogen stocks and sequestration rates are lower than in compared coal mining sites and spoils. The sequestration rates of the total sampled soil profile decreased with time from 57 g C m−2 year−1 and 4 g N m−2 year−1 for sites younger than 25 years to 46 g C m−2 year−1 and 3 g N m−2 year−1 for sites older than 50 years.

Exceptional preservation of organic matter and iron-organic colloidal mineralization in hydrothermal black smoker-type sulfide mineralization from the Paleoarchean seafloor

Fossil organic matter (OM) in Paleoarchean rocks is an invaluable tracer of ancient life, yet it is often contentious due to low preservation potentials of its original organic molecular characteristics under generally high metamorphic grades. This study reports on exceptionally preserved OM within black smoker-type sulfide mineralizations from the 3.24 billion-years-old Sulphur Springs volcanic-hosted massive sulfide deposit, East Pilbara Terrane, northwestern Australia. Fine scale mineralogical and organic molecular variations – documented by SEM and TEM techniques, Raman and FTIR Spectroscopy, as well as ToF-SIMS analysis – trace the formation of millimetre-scale pyritic hydrothermal orifices. Overmature OM (≳200–250 °C) enriched in aromatic hydrocarbons occurs within earliest formed colloform-banded pyrite that could have precipitated at high temperature upon mixing of hot hydrothermal fluids with cold seawater. In contrast, mature OM (within the catagenesis window; ∼100–150 °C) with lower proportions of aromatic hydrocarbons occasionally occurs alongside pyrite within barite near the inner paleofluid conduits of the hydrothermal orifices. A deposition of this OM generation from cooler fluids enriched in sulfate during waning hydrothermal activity is corroborated by its association with original mineralogy, particularly the occurrence of isolated nanoinclusions of OM within hydrothermal barite away from grain boundaries or fissures and cracks, which renders impossible an origin from post-depositional hydrocarbon migration. When compared to the overmature OM within colloform-banded pyrite, the better-preserved inner OM not only contains less abundant, smaller, and less ordered aromatic hydrocarbons, but also higher amounts of aliphatic molecules with longer chain lengths and higher proportions of carbonyl and amide functional groups. Although the latter characteristics are consistent with contributions by microbial biomass, abiotic origins are equally plausible because hydrothermal processes can produce OM with similar organic molecular attributes. Irrespective of these uncertainties on the ultimate sourcing of OM, common intergrowths of the cooler OM with nanoscopic iron oxides – hematite and lesser magnetite – hint at its hydrothermal deposition from colloidal particles that have been stabilized by iron-organic complexation. Further research is required to ascertain the significance of this process for the hydrothermal cycling and release of organic carbons and bound iron into the Paleoarchean oceans. Collectively, our results show that ancient marine hydrothermal systems can preserve OM with differing degrees of thermal degradation, which allows for insights into its sourcing, cycling, and deposition.

Изотопия углерода индивидуальных ароматических соединений нефти для понимания их геохимии

The article analyzes published and original data related to the carbon isotopic composition of individual aromatic compounds of fossil organic matter and oil. It has been shown that there is reliable evidence of the intramolecular isotopic heterogeneity of a number of molecules. For example the isotopically depleted carbon of the methyl group of alkylnaphthalenes and the terminal methyl of n-alkanes. The 13C inheritance from the biochemical precursor during the aromatization is also well documented in the example of diterpenes in the series abietic acid — dehydroabietane — simonellite — retene, as well as in the other terpene and steroid series. At the same time, there is evidence of carbon isotopic fractionation during the formation of several aromatic compounds from a single precursor. The increasing aromatization of the prebuild polycyclic structure does not change the 13C value of the molecule, and the formation of aromatic compounds with different numbers of aromatic rings in competing reactions leads to isotope differentiation in accordance with the thermodynamically determined distribution of carbon isotopes. If the suggestion is correct, it is the key to the understanding of specific petroleum aromatic hydrocarbons formation mechanism. It is possible that a comparison of 13C values for pairs of compounds formed during the transformation of one precursor will also provide information on the temperature conditions for the occurrence of the corresponding reactions.

Postdiagenetic Changes in Kerogen Properties and Type by Bacterial Oxidation and Dehydrogenation

A significant part of organic carbon found on the earth is deposited as fossil organic matter in the lithosphere. The most important reservoir of carbon is shale rocks enriched with organic matter in the form of kerogen created during diagenesis. The purpose of this study was to analyze whether the bacterial communities currently inhabiting the shale rocks have had any impact on the properties and type of kerogen. We used the shale rock located on the Fore-Sudetic Monocline, which is characterized by oil-prone kerogen type II. We were able to show that shale rock inhabited by bacterial communities are characterized by oxidized and dehydrated kerogen type III (gas-prone) and type IV (nonproductive, residual, and hydrogen-free). Bacterial communities inhabiting shale rock were dominated by heterotrophs of the Proteobacteria, Firmicutes, and Actinobacteria phyla. Additionally, we detected a number of protein sequences in the metaproteomes of bacterial communities matched with enzymes involved in the oxidative metabolism of aliphatic and aromatic hydrocarbons, which may potentially contribute to the postdiagenetic oxidation and dehydrogenation of kerogen. The kerogen transformation contributes to the mobilization of fossil carbon in the form of extractable bitumen dominated by oxidized organic compounds.

Lanthanide-Dependent Methanol Metabolism of a Proteobacteria-Dominated Community in a Light Lanthanide-Rich Deep Environment.

This study investigated the occurrence and diversity of proteobacterial XoxF-type methanol dehydrogenases (MDHs) in the microbial community that inhabits a fossil organic matter- and sedimentary lanthanide (Ln3+)-rich underground mine environment using a metagenomic and metaproteomic approach. A total of 8 XoxF-encoding genes (XoxF-EGs) and 14 protein sequences matching XoxF were identified. XoxF-type MDHs were produced by Alpha-, Beta-, and Gammaproteobacteria represented by the four orders Methylococcales, Nitrosomonadales, Rhizobiales, and Xanthomonadales. The highest number of XoxF-EG- and XoxF-matching protein sequences were affiliated with Nitrosomonadales and Rhizobiales, respectively. Among the identified XoxF-EGs, two belonged to the XoxF1 clade, five to the XoxF4 clade, and one to the XoxF5 clade, while seven of the identified XoxF proteins belonged to the XoxF1 clade, four to the XoxF4 clade, and three to the XoxF5 clade. Moreover, the accumulation of light lanthanides and the presence of methanol in the microbial mat were confirmed. This study is the first to show the occurrence of XoxF in the metagenome and metaproteome of a deep microbial community colonizing a fossil organic matter- and light lanthanide-rich sedimentary environment. The presented results broaden our knowledge of the ecology of XoxF-producing bacteria as well as of the distribution and diversity of these enzymes in the natural environment.

Geochemistry of High-Molecular Weight Dimethylalkanes

Abstract —The homologous series of high-molecular weight dimethylalkanes (HMWDMAs) with either odd- or even-numbered carbon chains in the range from C19–20 to C30–31 have been identified in organic matter from recent and partially lithified deposits of Siberia and the Russian Platform by chromatography–mass spectrometry. The first homologous series is represented by even-numbered 3,4-HMWDMAs followed by the alternation of odd-numbered 3,5-HMWDMAs, even-numbered 3,6-HMWDMAs, and odd-numbered 3,7-HMWDMAs. The most abundant are 3,7-dimethylalkanes. The microbial origin of high-molecular weight dimethylalkanes is the most likely explanation for their presence in the fossil organic matter. The precursors of HMWDMAs might have been tetra- and diether lipids of archaea and bacteria. It is assumed that HMWDMAs and other immature hydrocarbons from great depths (SV-27 and SG-6 superdeep boreholes) result from the decomposition of asphaltenes, which occluded the related compounds inside their structure during the early stages of generation and carried them unchanged throughout the “oil window”.

New methods of acid hydrolysis of cellulose and plant raw materials

Prospects for the development of hydrolysis production are determined by the relevance of industrial use of plant biomass to replace the declining reserves of fossil organic raw materials and increasing demand for ethanol, especially for its use as automobile fuel, protein-containing feed additives that compensate for protein deficiency in feed production, and other products. Based on the review of the research results presented in the scientific literature, the analysis of modern methods of liquid-phase acid hydrolysis of cellulose and various types of plant raw materials, including those that differ from traditional ones, is performed. The main directions of increasing its efficiency through the use of new catalytic systems and process conditions are identified. It is shown that the most promising methods for obtaining monosaccharides in hydrolytic processing of cellulose and microcrystalline cellulose, pentosan-containing agricultural waste and wood, are methods for carrying out the process at elevated and supercritical temperatures (high-temperature hydrolysis), the use of new types of solid-acid catalysts and ionic liquids.

Hypothesis about physical-chemical nature of gas-dynamic phenomena in coal mines

Practical experience in the development of a gas-saturated coal-rock massif, as well as the results of scientific research, point to the imperfection of the existing ideas regarding the processes in the extremely stressed coal-rock massif, mechanisms of the occurrence and behavior of gas-dynamic phenomena (GDP). The conducted analysis for the problem state regarding the nature and mechanism of sudden outbursts of coal, rocks and gas, in general, confirm that the outburst hazard was due to the complex interaction of three main natural factors (stress state, gas factor and physical-mechanical properties of rocks) with technological ones, and the formation of outburst hazardous conditions occurs in geological environments that are characterized by certain properties and conditions. The purpose of the paper is to obtain new theoretical understanding of the GDP nature with taking into account geological conditions and the impact of external factors by developing a hypothesis regarding the physicochemical nature of the GDP. It is proved that relief of stresses arisen in the molecular structure under the impact of geological factors leads to the activation of relaxation processes in the substance. The relaxation of the accumulated energy system results in structural transformations with the release of low-molecular-weight compounds. According to this pattern, accumulation of gases genetically connected with fossil organic matter and the emergence of gas-dynamic phenomena.is formed in the coal-rock massif. The key point of the hypothesis is that partial stress relief of the coal-rock massif creates in the fractured zones of the coal bed conditions for relaxation of elastic energy accumulated in the molecular structure of coal, hence, promoting the activation of structural transformations by the free-radical mechanism, which results in the release of low-molecular-weight compounds (methane, in particular). Under appropriate conditions, in the zone of relaxation of elastic deformations, the process can assume an avalanche character, namely, initiate sudden outbursts of coal and gas. According to the physicochemical model of methane release in coal under the impact of geomechanical, geological, and technogenic factors, which is proposed within the framework of this work, partial discharge creates in the coal bed conditions for relaxation of the elastic energy accumulated in the molecular structure of coal. That is, it promotes the activation of structural transformations by the free-radical mechanism, the result of which is the release of low-molecular-weight compounds (methane). Under the condition of sufficiently high fracturing of the elastic deformation zone, the process acquires an avalanche character, that is, sudden outbursts of coal and gas are developed. Keywords: coal, coal mines, gas-dynamic phenomena, outbursts of coal and gas, stress-strain state.

Elucidation of the macromolecular composition of fossil biopolymers using Py-GC×GC-TOFMS

In recent times, the limits of traditional Py-GC-MS techniques in evaluating the macromolecular compositions of biopolymers have proved to be more apparent – particularly in those samples containing complex, structurally similar organic molecules, often producing large areas of unresolved complex mixtures (UCM). In this paper, we compare the use of pyrolysis comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (Py-GC×GC-TOFMS) with conventional Py-GC-MS analyses and attempt to showcase the full potential of this technique by analyzing different fossil organic materials – algal-derived Tasmanites, Ordovician microfossil Gloeocapsomorpha prisca and terrestrial plant-derived resin. With all three fossil samples, Py-GC×GC-TOFMS was able to offer a higher degree of compound separation and detection of more complex compounds. Sulphur and oxygen-bearing polar compounds were clearly separated into different homologous series. Thus, this method bypassed the problem created by the UCMs in traditional Py-GC-MS in the case of G. prisca and Tasmanites, while resolving several biomarkers in the case of the resin which aided chemotaxonomic classification. We find that Py-GC×GC-TOFMS provides a greater variety of compounds at enhanced resolution levels than conventional Py-GC-MS methods and is more suited to analyzing samples with larger variety of chemical structures and functional groups with greater confidence, particularly in unknown samples. It can thus provide the analytical capability to better characterize the chemistry of kerogens, which will help in assessments of hydrocarbon source properties and may provide new avenues to interpretation in paleobiological studies.

Surface-Enhanced Raman Scattering Microspectroscopy Enables the Direct Characterization of Biomineral-Associated Organic Material on Single Calcareous Microskeletons.

Biominerals are composite materials with inorganic and organic components. The latter provide insights into how organisms control mineralization and, if derived from micro/nannofossils, into past climates. Many calcifying organisms cannot be cultured or are extinct; the only materials available for their study are therefore complex environmental samples in which the organism of interest may only be a minor component. There is currently no method for characterizing the biomineral-associated organic material from single particles within such assemblages, so its compositional diversity is unknown. Focusing on coccoliths, we demonstrate that surface-enhanced Raman scattering microspectroscopy can be used to determine the origin and composition of fossil organic matter at the single-particle level in a heterogeneous micro/nannofossil assemblage. This approach may find applications in the study of micro/nannofossil assemblages and uncultivated species, providing evolutionary insights into the macromolecular repertoire involved in biomineralization.

Phylogenetic and physiological signals in metazoan fossil biomolecules.

Proteins, lipids, and sugars establish animal form and function. However, the preservation of biological signals in fossil organic matter is poorly understood. Here, we used high-resolution in situ Raman microspectroscopy to analyze the molecular compositions of 113 Phanerozoic metazoan fossils and sediments. Proteins, lipids, and sugars converge in composition during fossilization through lipoxidation and glycoxidation to form endogenous N-, O-, and S-heterocyclic polymers. Nonetheless, multivariate spectral analysis reveals molecular heterogeneities: The relative abundance of glycoxidation and lipoxidation products distinguishes different tissue types. Preserved chelating ligands are diagnostic of different modes of biomineralization. Amino acid-specific fossilization products retain phylogenetic information and capture higher-rank metazoan relationships. Molecular signals survive in deep time and provide a powerful tool for reconstructing the evolutionary history of animals.

Toarcian climate and carbon cycle perturbations – its impact on sea-level changes, enhanced mobilization and oxidation of fossil organic matter

Organic geochemistry and palynology reveal major organofacies changes in the marginal marine Polish Basin during the early Toarcian linked to changes in environmental conditions. Increasing water salinity and enhanced biomass contributions from phytoplankton, adopted to brackish conditions, attest to periodic marine ingressions into the paralic, hyposaline Polish Basin. Marine ingressions occurred upon reoccurring sea level rises concomitant with i) the Pliensbachian-Toarcian boundary carbon isotope excursion (Pl-Toa-CIE) and ii) the stepped Toarcian carbon isotope excursion (Toa-CIE), the latter marking the Toarcian Oceanic Anoxic Event (Toa-OAE). Strata with marine influences indicate an intermittent connection of the Polish Basin with the Tethys and attest to a close correlation between regional shoreline progradation and evolution of global climate and sea-level. Organic geochemistry indicated the link between sea level fluctuations and the Toa-CIEs, although in some areas of the Polish Basin the sea level rise was balanced by massively increased sediment delivery, caused by enhanced hydrological cycling that lead to intensified weathering and erosion in the hinterland. Enhanced hydrological cycling further led to the remobilization of organic matter of pre-Toarcian age. This points to erosion of older organic-rich rocks containing significant abundances of marine and terrestrial organic matter that was partly oxidized and re-deposited along with autochthonous Toarcian organic matter. Provenance areas identified point to two main sources, most likely Carboniferous terrestrial/paralic and Ordovician/Silurian marine sediments. Fossil organic matter should be considered as additional source in Toarcian carbon cycling, particularly in times of enhanced hydrological cycling, erosion and weathering. Remobilization of sedimentary fossil carbon has not been hitherto considered as a carbon source during the Toa-OAE.

New preparation techniques for molecular and in-situ analysis of ancient organic micro- and nanostructures.

Organic microfossils preserved in three dimensions in transparent mineral matrices such as cherts/quartzites, phosphates, or carbonates are best studied in petrographic thin sections. Moreover, microscale mass spectrometry techniques commonly require flat, polished surfaces to minimize analytical bias. However, contamination by epoxy resin in traditional petrographic sections is problematic for the geochemical study of the kerogen in these microfossils and more generally for the in situ analysis of fossil organic matter. Here, we show that epoxy contamination has a molecular signature that is difficult to distinguish from kerogen with time-of-flight secondary ion mass spectrometry (ToF-SIMS). This contamination appears pervasive in organic microstructures embedded in micro- to nano-crystalline carbonate. To solve this problem, a new semi-thin section preparation protocol without resin medium was developed for micro- to nanoscale in situ investigation of insoluble organic matter. We show that these sections are suited for microscopic observation of Proterozoic microfossils in cherts. ToF-SIMS reveals that these sections are free of pollution after final removal of a <10nm layer of contamination using low-dose ion sputtering. ToF-SIMS maps of fragments from aliphatic and aromatic molecules and organic sulfur are correlated with the spatial distribution of organic microlaminae in a Jurassic stromatolite. Hydrocarbon-derived ions also appeared correlated with kerogenous microstructures in Archean cherts. These developments in analytical procedures should help future investigations of organic matter and in particular, microfossils, by allowing the spatial correlation of microscopy, spectroscopy, precise isotopic microanalyses, and novel molecular microanalyses such as ToF-SIMS.

A comparative study of total organic carbon-δ13C signatures in the Triassic–Jurassic transitional beds of the Central European Basin and western Tethys shelf seas

Stratigraphic studies are an integral component in understanding the chronology of events that led to the end-Triassic mass extinction, by resolving causal relationships between environmental upheavals and biotic response. Successful correlation of Triassic–Jurassic (Tr–J) successions is complicated by the disappearance of macro-fossils that are otherwise central components in stratigraphic studies. This problem is exacerbated in multiple Tr–J sections situated in Europe, where the so-called “Event Beds” – assumed to demarcate the extinction interval – are virtually devoid of fossils. An alternative stratigraphic approach entails the reconstruction of carbon isotope records, where stratigraphic fluctuations in carbon isotope composition are considered to track changes in the global biogeochemical carbon cycle. The predominance of carbonate-lean sections has prompted the reconstruction of total organic carbon (TOC)-based carbon isotope records. However, bulk rock derived TOC is the diagenetically stabilized remnant of organic components that accumulated on the sea floor, and which can originate from multiple sources. In this study, we assess long-term TOC-based carbon isotope trends at two sites: Bonenburg (Central European Basin) and Kuhjoch (the Tr–J Global Stratotype Section and Point; western Tethys shelf seas). We focus on the TOC 13C-enrichment of the Event Beds with the aim of deciphering stratigraphic fluctuations in relation to their main driver (the exogenic carbon pool versus organic matter source changes). By studying the systematic co-variance of several sedimentary parameters (TOC, total nitrogen [TN], and the palynomorph composition), we infer that the TOC composition is possibly characterized by insignificant organic matter source changes in terms of the marine and terrestrial organic carbon contributions. By contrast, a clay mineralogical shift to more K-depleted minerals as well as the elevated occurrence of wood fragments in the Event Beds suggest a terrestrial organic matter source shift from immature substrates to substrates predominated by “pre-aged” or “fossil organic matter” under a changing continental weathering regime. This outcome urges for reservations when interpreting TOC-based carbon isotope records in terms of global C-cycle perturbations, especially when coinciding with lithological and mineralogical changes. On a more positive note, the shift towards positive carbon isotope values appears to be a recurring feature, possibly testifying to a globally significant climate-controlled weathering regime shift.

Gas generation by coal matter in contemporary conditions

A new approach for the study of processes at the atomic-molecular level occurring in the current situation in fossil carbonized organics was proposed. A new phenomenological model of physicochemical transformations in a metastable coal substance with the emission of fluids has been developed. The proposed physic/chemical model is based on the genetic connection of coal methane with fossil organic matter and determines the conditions for the activation of structural transformations in coalmines. This model describes the possible options for the coal/gas system development in the current situation. The accumulation of thermal and mechanical energy by coal in the form of structural stresses in an amount, sufficient to activate free-radical reactions, was experimentally established. In the undisturbed coalrock massif the processes of the coal molecular structure transformation have the relaxation character. The result of relaxation of the accumulated energy in the conditions of a gas-saturated coalrock massif is the methane generation by coal. Gas generation in the process of coalification, in its essence, is the energy response of the system to the action of external geomechanical options (temperature and pressure), by the way of releasing the accumulated additional energy with the emission of gaseous products and the destruction of the solid phase in the organic matter of the coal.

Steam reforming of shale gas over Al2O3 supported Ni-Cu nano-catalysts

Hydrogen is a clean energy carrier that does not exist in nature in its pure form and should be acquired from other fossil fuels and organic materials. In this article, an experimental study was done to evaluate the potential of steam reforming of shale gas over Al2O3 supported Ni-Cu nano-catalysts for hydrogen production. By increasing reaction temperature, the shale gas conversion continuously increased. The introduction of additional steam to reactor had a positive impact on hydrogen yield, but its impact was not as significant as reaction temperature. As a result, the catalytic activity of Ni-Cu/Al2O3 prepared by impregnation was higher than the Ni-Cu/Al2O3 prepared by co-precipitation method.