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ABSTRACT As the exploration of deep‐seated oil and gas resources in the Turpan‐Hami Basin intensifies, there is an urgent need to thoroughly depict the geological characteristics of newly uncovered, underexplored strata in sub‐sag centers. This study undertakes the inaugural systematic geochemical analysis of mudstones atop the Sangonghe Formation, including palynological identification, maceral identification, biomarker analysis, total organic carbon (TOC) analysis, and pyrolysis. The findings reveal that the mudstone sequence, as the target layer, was deposited in a warm and moist paleoclimate and a weakly reducing to weakly oxidising saline water environment, fostering the growth of prolific algae and bacteria, thus ensuring substantial foundational materials for source rock formation. The organic matter in the mudstone sequence displays pronounced laminar accumulation. Despite the overall modest abundance, the organic matter features notable hydrocarbon‐generating potential per unit of organic carbon and favourable types. Humic‐sapropelic kerogens (type II1) are found in the mudstones, with organic matter generally reaching a mature to highly mature stage. These characteristics establish the mudstones as effective source rocks, furthermore, the hydrocarbon expulsion in the Xishanyao Formation precedes that of the Sangonghe Formation and that both formations constitute a sequential process in terms of hydrocarbon generation and expulsion timing and hydrocarbon contribution. Reanalyzing this mudstone sequence not only revises prior geological understanding of it as direct cap rocks, but also facilitates the reclassification of deep‐seated strata into three distinct petroleum systems. Centered around this source rock layer, dual modes, namely the “lower‐source rock and upper‐reservoir” and the “ lower‐reservoir and upper‐source rock” modes can be formed. These new insights will offer profound implications for hydrocarbon resource evaluation and future hydrocarbon exploration endeavours in the Shuixigou Group within the Taibei sag. [ABSTRACT FROM AUTHOR]

Mine environments in boreal and sub-boreal zones are expected to experience extreme weather events, increases in temperature, and shifts in precipitation patterns. Climate change impacts on geochemical stability of tailings contaminants and reclamation structures have been identified as important climate-related challenges to Canadian mining sector. Adapting current reclamation strategies for climate change will improve long-term efficiency and viability of mine tailings remediation/restoration strategies under a changing climate. Accordingly, mesocosm experiments were conducted to investigate associations of climate-driven shifts in microbial communities and functions with changes in the geochemistry of organic covers and underlying tailings. Our results show that warming appears to significantly reduce C:N of organic cover and promote infiltration of nitrogen into deeper, unoxidized strata of underlying tailings. We also observed an increase in the abundance of some nitrate reducers and sulfide oxidizers in microbial communities in underlying tailings. These results raise the concern that warming might trigger oxidation of sulfide minerals (linked to nitrate reduction) in deeper unoxidized strata where the oxygen has been eliminated. Therefore, it would be necessary to have monitoring programs to track functionality of covers in response to climate change conditions. These findings have implications for development of climate resilient mine tailings remediation/restoration strategies. [ABSTRACT FROM AUTHOR]

The understanding of the spatial distribution of soil organic carbon (SOC) and its influencing factors is crucial for comprehending the global carbon cycle. However, the impact of soil geochemical and climatic conditions on SOC remains limited, particularly in dryland farming areas. In this study, we aimed to enhance the understanding of the factors influencing the distribution of SOC in the drylands of the Songliao Plain, Northeast China. A dataset comprising 35,188 measured soil samples was used to map the SOC distribution in the region. Multiple linear regression (MLR) and random forest models (RFM) were employed to assess the importance of driving indicators for SOC. We also carried out partial correlation and path analyses to further investigate the relationship between climate and geochemistry. The SOC content in dryland soils of the Songliao Plain ranged from 0.05% to 11.63%, with a mean value of 1.47% ± 0.90%. There was a notable increasing trend in SOC content from the southwest to the northeast regions. The results of MLR and RFM revealed that temperature was the most critical factor, demonstrating a significant negative correlation with SOC content. Additionally, iron oxide was the most important soil geochemical indicator affecting SOC variability. Our research further suggested that climate may exert an indirect influence on SOC concentrations through its effect on geochemical properties of soil. These insights highlight the importance of considering both the direct and indirect impact of climate in predicting the SOC under future climate change. [ABSTRACT FROM AUTHOR]

Cambrian shales in China and elsewhere contain abundant oil and gas resources. However, due to its deep burial and limited outcrop, there has been relatively little research conducted on it. The Cambrian shale of the Tadong low uplift in the Tarim Basin of western China, specifically the Xidashan–Xishanbulake Formation (Fm.) and overlying Moheershan Fm. provide a case study through the use of organic petrology, mineralogy, organic and elemental geochemistry, with the aim of analyzing and exploring the hydrocarbon generation potential (PG) and organic matter (OM) enrichment mechanisms within these shale formations. The results indicate that: (1) the Cambrian shale of the Tadong low uplift exhibits relatively dispersed OM that consists of vitrinite‐like macerals and solid bitumen. These formations have a higher content of quartz and are primarily composed of silica‐based lithology; (2) shale samples from the Xidashan–Xishanbulake and Moheershan formations demonstrate high total organic carbon (TOC) and low pyrolytic hydrocarbon content (S2) content. The OM is predominantly type I and type II kerogens, indicating a high level of maturation in the wet gas period. These shales have undergone extensive hydrocarbon generation, showing characteristics of relatively poor PG; (3) the sedimentary environments of the Xidashan–Xishanbulake and Moheershan formations in the Tadong low uplift are similar. They were deposited in warm and humid climatic conditions, in oxygen‐deficient environments, with stable terrigenous inputs, high paleoproductivity, high paleosalinity, weak water‐holding capacity, and no significant hydrothermal activity; and (4) the relationship between TOC and the paleoproductivity parameter (P/Ti) is most significant in the Lower Cambrian Xidashan–Xishanbulake Fm., whereas correlation with other indicators is not evident. This suggests a productivity‐driven OM enrichment model, where input of land‐derived material was relatively small during the Middle Cambrian, and the ancient water exhibited lower salinity. A comprehensive pattern was formed under the combined control of paleoproductivity and preservation conditions. This study provides valuable guidance for oil and gas exploration in the Tarim Basin. [ABSTRACT FROM AUTHOR]

This study presents an integrated approach using organic geochemistry and incident-light organic petrographic microscopy techniques to characterize the kerogen type, hydrocarbon potential, thermal maturity, and effective depositional environment of the Eocene Liushagang Formation intervals in the western Huangtong Sag, eastern Bailian Sag, central Huachang Sub-uplift, and Southern Slope Zone area in the Fushan Depression, Beibuwan Basin. The results show that the hydrocarbon potential of these organic-rich lacustrine shale areas is mainly dependent on the depositional environment and the present-day burial depth of sediments. Oscillations and transitions between (i) rocks with dominant allochthonous organic matter (including primary/reworked vitrinite and inertinite macerals and terrestrial debris particles) representing a large influence of continental sediments (e.g., source supply direction) and (ii) rocks with dominant autochthonous organic matter (e.g., alginite) indicate a distal and stable lacustrine basin depositional environment. The source rock thickness ranges from 40.1 to 387.4 m. The average TOC of the Liushagang Formation in the Fushan Sag is between 0.98% and 2.00%, with the highest organic matter abundance being in the first and second sections of the Liushagang Formation, presenting as high-quality source rocks. The organic matter is predominantly Type II1 and Type II2. The highest vitrinite reflectance (1.14%) is in the Huangtong and Bailian Sags. The source rocks of the second section of the Liushagang Formation are primary hydrocarbon generators, contributing 55.11% of the total generation. Hydrocarbon sequestration peaks at %Ro 0.80%, with a maximum efficiency of 97.7%. The cumulative hydrocarbon generation of the Liushagang Formation is 134.10 × 108 tons, with 50.52 × 108 tons having been expelled and 83.58 × 108 tons remaining. E2L2X and E2L2S have maximum hydrocarbon displacement intensities of 184.22 × 104 t/km² and 45.39 × 104 t/km², respectively, with cumulative displacements of 52.99 × 108 tons and 15.58 × 108 tons. The oil and gas accumulation system is highly prospective, showing significant exploration potential. [ABSTRACT FROM AUTHOR]

Migration pathways and distances of the oils in reservoir are thought to affect the distribution of pyrrolic compounds such as carbazole, its alkyl derivatives (alkylated carbazoles) and benzocarbazoles, although other factors, including maturity and depositional environments may also affect the distribution of these organic nitrogen compounds. In this study, 14 oil samples produced from conventional reservoirs in Pauls Valley, south Oklahoma were investigated using organic geochemical techniques. The sterane and hopane fingerprints suggest that most of the oils were sourced from the Devonian Woodford shale. Maturity parameters consistently indicate that the maturity level of the studied samples are all of similar maturity (Rc = ∼0.7%), suggesting the distribution of the organic nitrogen organic compounds is possibly reflecting variations in relative migration distances. The distribution of alkylcarbazoles revealed a preferential enrichment during migration, with the nitrogen-shielded alkylcarbazole tending to be enriched relative to the nitrogen-semi-shielded alkylcarbozoles particularly in oils produced close to the Arbuckle uplift to the east. Correspondingly, another family of pyrrolic compounds, benzocarbazoles, whose distributions also indicated that the Pauls Valley Woodford oils came from deeper part of the Anadarko Basin as the benzo-[a]/([a]+[c])-carbazole ratios decrease eastwards. In more specific migration systems, although the pyrrolic compound indicators are potentially disturbed by the structural complexes, the general migration directions suggest that the studied oils in Pauls Valley Hunton uplift were sourced from the deep basin area, and migrate upwards in porous sediments due to the buoyancy. This study investigates the feasibility of using pyrrolic compounds to estimate relative migration distances and will aid in the interpretation of migration history by using the distribution of carbazole, alkylated carbazoles, benzocarbazoles isomers in the Anadarko and Ardmore Basin petroleum systems. [ABSTRACT FROM AUTHOR]

The mudstone, gray tuffite and carbonaceous shale in the Upper Carboniferous Batamayineishan Formation (Bashan Formation) are essential source rocks for the volcanic reservoir in eastern Junggar, northwestern China. The kerogen components, vitrinite reflectance, Rock-Eval pyrolysis, lipid biomarkers and isotope compositions were measured to understand the provenance and depositional environment of Bashan Formation under the background of volcanic activities. There were 10 and 4 periods of volcanic eruptions identified in the wells CS and DZ, respectively. The source rocks developed in the late or intermittent phase of volcanic activity. The original island arcs of the Early Carboniferous evolved into the Wucaiwan sag and the Dishuiquan sag in the Bashan Formation. The Wucaiwan sag inherited the restricted, closed residual sea, which had a slightly anoxic and hypersaline environment. The Dishuiquan sag was generally an oxidizing lacustrine environment, influenced by a marine transgression that may have occurred at the end of the DZIII period during the Late Carboniferous. Although the total organic matter decreased due to the volcanic eruption, ash could cause an increase of aquatic organisms, coinciding with increases in salinity and reducibility in the Dishuiquan sag. [ABSTRACT FROM AUTHOR]

The document is an index of editorial contents for Volume 47 of the Journal of Petroleum Geology, published in 2024. It includes articles on various topics such as the structural style and timing of folds in Iran, lacustrine source rocks in Argentina, the modern oil industry in Iran, the Arabia-Eurasia collision zone in Iran, and the influence of Pleistocene glaciation on petroleum systems in the Barents Sea. The document also lists the authors and referees who contributed to the journal. [Extracted from the article]

This study employs comprehensive source rock evaluation using seismic inversion, rock-eval pyrolysis, organic petrography and basin modeling techniques. The kerogen type is determined by using the Van Krevelen diagram, confirming Bahu-01, Nandpur-01 and Zakria-01 wells have kerogen type III, whereas Panjpir-01 well exhibits kerogen type II to III. The TOC was calculated using core data from (34) samples by employing organic geochemistry technique and post stack seismic inversion, applied on 2D seismic data. Bahu-01 well indicates poor source rock potential, with an average TOC value of 0.34%. In contrast, Panjpir-01 and Nandpur-01 wells represent moderate to good organic richness, with average TOC values of 1.25% and 1.36%, respectively. However, Zakria-01 well with a TOC of 0.72%, exhibits fair organic richness. The Maturity estimation from organic petrography and basin modeling reveals that the Bahu-01, Panjpir-01, and Nandpur-01 wells have average vitrinite reflectance (%Ro) values below 0.50, indicating immature source rock. In contrast, the average %Ro value for the Zakria-01 well is 0.63, confirming the source maturity in the early oil window, with peak generation occurring during Eocene age. Finally, the source rock evaluation proves the source is mature in the western part only and future hydrocarbon exploration should be focused in the western area. The integrated source rock evaluation approach is novel in Punjab Platform. The diverse methodologies enhanced our understanding about source rock characteristics for pursuing hydrocarbon resources. An integrated approach will also provide valuable insights for hydrocarbon exploration in numerous other basins worldwide. [ABSTRACT FROM AUTHOR]

The Upper Miocene Bongaya Formation coal, carbonaceous shale, and shale sediments were collected to investigate their origin, types, and maturity. The main objectives of this study were to verify and update previous claim of possible hydrocarbon showings and to gain new insights about the petroleum potential using different geochemical analysis approach. The primary methodology used in this study is the pyrolysis technique and coupled with petrographic analysis. The bulk geochemistry results revealed that the Bongaya sediments serve as favorable source rock, with the total organic carbon (TOC) content ranging from 0.90 to 63.10 wt% by weight, indicating fair to excellent organic richness. The coal samples exhibited the highest TOC values, followed by carbonaceous shale samples, while shale and coal laminated with sandstone samples displayed fair TOC amounts. Most of the Bongaya sediments analyzed in this study exhibited hydrogen index (HI) values of less than 200 mg HC/g TOC, indicating Type III organic matter, which signifies a significant influence of terrestrial organic matter. However, three coals displayed comparatively higher pyrolysis HI values, corroborated by Pyrolysis gas-chromatography (Py-GC) results and maceral types, indicating a mixture of Type II/III kerogen. This suggests that the Bongaya Formation sediment has the potential to generate gas with minor oil. Maceral analysis also revealed that most of the coal samples contained a high content of resinite maceral, which explains the waxy composition of the oil. The organic matter in the analyzed Bongaya sediments was found to be immature for petroleum generation, as evidenced by low huminite reflectance data (lower than 0.50% VR) and Tmax values between 372 and 432 °C. Consequently, the kerogen in the studied onshore Bongaya sediments has yet to enter the hydrocarbon cracking (catagenesis) phase before expelling petroleum. Therefore, it is essential to consider the offshore equivalent Bongaya sediments, which may be laterally extended offshore and buried at deeper depths to attain optimal maturity for hydrocarbon generation. [ABSTRACT FROM AUTHOR]

The present study focused on the Permian to Jurassic sequence in the Northern Highlands area, NW Jordan. The Permian to Jurassic sequence in this area is thick and deeply buried, consisting mainly of carbonate intercalated with clastic shale. This study integrated various datasets, including total organic carbon (TOC, wt%), Rock-Eval pyrolysis, visual kerogen examination, gross composition, lipid biomarkers, vitrinite reflectance (VRo%), and bottom-hole temperature measurements. The main aim was to investigate the source rock characteristics of these strata regarding organic richness, kerogen type, depositional setting, thermal maturity, and hydrocarbon generation timing. The Permian strata are poor to fair source rocks, primarily containing kerogen type (KT) III. They are immature in the AJ-1 well and over-mature in the NH-2 well. The Upper Triassic strata are poor source rocks in the NH-1 well and fair to marginally good source rocks in the NH-2 well, containing highly mature terrestrial KT III. These strata are immature to early mature in the AJ-1 well and at the peak oil window stage in the NH-2 well. The Jurassic strata are poor source rocks, dominated by KT III and KT II-III. They are immature to early mature in the AJ-1 well and have reached the oil window in the NH-2 well. Biomarker-related ratios indicate that the Upper Triassic oils and Jurassic samples are source rocks that received mainly terrestrial organic input accumulated in shallow marine environments under highly reducing conditions. These strata are composed mostly of clay-rich lithologies with evidence of deposition in hypersaline and/or stratified water columns. 1D basin models revealed that the Upper Triassic strata reached the peak oil window from the Early Cretaceous (~80 Ma) to the present day in the NH-1 well and from ~130 Ma (Early Cretaceous) to ~90 Ma (Late Cretaceous) in the NH-2 well, with the late stage of hydrocarbon generation continuing from ~90 Ma to the present time. The present-day transformation ratio equals 77% in the Upper Triassic source rocks, suggesting that these rocks have expelled substantial volumes of hydrocarbons in the NH-2 well. To achieve future successful hydrocarbon discoveries in NW Jordan, accurate seismic studies and further geochemical analyses are recommended to precisely define the migration pathways. [ABSTRACT FROM AUTHOR]

Hydrothermal activity is widespread in sedimentary basins, but its dual effects (chemistry and temperature) on shale reservoirs are rarely discussed. In this research, we systematically collected 33 well core samples from Q1 to Q9 units in Gulong Sag, Songliao Basin, and analyzed them using a variety of analytical techniques, including a field emission scanning electron microscopy (FE-SEM), an energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), and stable C-O isotopes. Combined with the collected vitrinite reflectance (Ro), total organic carbon (TOC), and soluble hydrocarbon content data, which is the sum of free oil (pyrolysis S1) and sorb oil content (pyrolysis S2), the results show that (1) Q4 and Q8 units have large amounts of hydrothermal minerals, and its C-O isotope obviously shifts to negative, which implied those units are the main hydrothermal fluid influence area; (2) the hydrothermal activity occurred in the late depositional period of Q1–Q9 units such that its geochemistry has little effect on the proliferation of algae blooms, but its high temperature calculated by δ18O temperature formulas (around 208 °C) promoted the organic matter maturation process around Q4 and Q8; and (3) the overpressure caused by hydrothermal activity protected the shale reservoir and minimized the decrease in mineral reservoir brittleness index caused by hydrothermal fluid influence. We suggest that the shale reservoir affected by hydrothermal fluid will become a good geology "dessert", and its upper and/or lower bounds can form an engineering "dessert" due to the precipitation of large amounts of brittle carbonate minerals. [ABSTRACT FROM AUTHOR]

The Early Jurassic was primarily a greenhouse phase in Earth's history. Previous studies have predominantly focused on marine strata in the Tethyan Ocean, but continental records outside of Europe are still poorly understood, which has hindered a thorough understanding of its climate dynamics. To address this gap, organic, inorganic, and isotope geochemical analyses, along with mineralogical and sedimentological assessments, were conducted on samples from the Quemo Co Formation of well QZ-16 in the Qiangtang Basin (Eastern Tethys). This study aimed to investigate carbon cycle perturbations and consequences of redox conditions and paleosalinity within a lacustrine system during the Early Jurassic. The carbon isotope profile of well QZ-16 exhibited a long-term negative excursion of ca. −3.83‰ in lacustrine sediments, with relatively heavy δ13Corg values and small excursion magnitudes. Enhanced terrigenous input, as indicated by detrital proxies such as Si/Al, Ti/Al, and Zr/Al, was driven by accelerated continental weathering during the carbon isotope excursions. The presence of coarse-grained, pelitic siltstone deposits coincided with the onset of these negative carbon isotope excursions. Sr/Ba ratios (0.05–3.64, avg. 0.73) suggest a brackish to freshwater salinity regime within the third member, implying that the deposition of the Quemo Co Formation was influenced by both freshwater and seawater inputs. Most enrichment factors (VEF, ZnEF, NiEF) having a value below 1.0 and Corg/P ratios less than 50 indicate that the lacustrine environment was characterized by predominantly oxidizing conditions, particularly during the early Toarcian negative carbon isotope excursion (T-NCIE). Despite the record of the T-NCIE event, enhanced respiration in bottom and pore waters indicates that the Toarcian Oceanic Anoxic Event (T-OAE) was absent in this part of the eastern Tethys Ocean. The recorded Early Jurassic environmental settings in the Qiangtang Basin lacustrine system exhibit a close association with the T-CIE event (183 Ma), providing insights into the complex interplay between carbon cycle perturbation, climate, weathering, and biological processes during this greenhouse period. [ABSTRACT FROM AUTHOR]

Tectonism is one of the dominant factors affecting the shale pore structure. However, the control of shale pore structure by tectonic movements is still controversial, which limits the research progress of shale gas accumulation mechanism in the complex tectonic region of southern China. In this study, 34 samples were collected from two exploratory wells located in different tectonic locations. Diverse experiments, e.g., organic geochemistry, XRD analysis, FE-SEM, low-pressure gas adsorption, and high-pressure mercury intrusion, were conducted to fully characterize the shale reservoir. The TOC, Ro, and mineral composition of the shale samples between the two wells are similar, which reflects that the shale samples of the two wells have proximate pores-generating capacity and pores-supporting capacity. However, the pore characteristics of shale samples from two wells are significantly different. Compared with the stabilized zone shale, the porosity, pore volume, and specific surface area of the deformed zone shale were reduced by 60.61%, 64.85%, and 27.81%, respectively. Moreover, the macroscopic and fine pores were reduced by 54.01% and 84.95%, respectively. Fault activity and uplift denudation are not conducive to pore preservation, and the rigid basement of Huangling uplift can promote pore preservation. These three factors are important reasons for controlling the difference in pore structure between two wells shales. We established a conceptual model of shale pores evolution under different tectonic preservation conditions. This study is significant to clarify the scale of shale gas formation and enrichment in complex tectonic regions, and helps in the selection of shale sweet spots. [ABSTRACT FROM AUTHOR]

The Rhynie Chert (Lower Devonian, Scotland) hosts a remarkably well‐preserved early terrestrial ecosystem. Organisms including plants, fungi, arthropods, and bacteria were rapidly silicified due to inundation by silica‐rich hot spring fluids. Exceptional molecular preservation has been noted by many authors, including some of the oldest evidence of lignin in the fossil record. The evolution of lignin was a critical factor in the diversification of land plants, providing structural support and defense against herbivores and microbes. However, the timing of the evolution of lignin decay processes remains unclear. Studies placing this event near the end of the Carboniferous are contradicted by evidence for fungal pathogenesis in Devonian plant fossils, including from the Rhynie Chert. We conducted organic geochemical analyses on a Rhynie Chert sample, including hydropyrolysis (HyPy) of kerogen and high‐resolution mass spectrometric mapping of a thin section, to elucidate the relationship between lignin and the potential fungal marker perylene. HyPy of kerogen showed an increase in relative abundance of perylene supporting its entrapment within the silicate matrix of the chert. Lignin monomers were isolated through an alkaline oxidation process, showing a distribution dominated by H‐type monomers. G‐ and S‐type monomers were also detected, preserved by rapid silicification. Polycyclic aromatic hydrocarbons including perylene, a known marker for lignin‐degrading fungi, were also concentrated in the kerogen and found to be localized within silicified plant fragments. Our results strongly link perylene in the Rhynie Chert to the activity of phytopathogenic fungi, demonstrating the importance of fungal degradation processes as far back as the Early Devonian. [ABSTRACT FROM AUTHOR]

An organic geochemical, petrographical, and palynological evaluation was conducted on 30 claystone outcrop samples of the Toraja Formation, along with a geochemical analysis of an oil seep in the Enrekang Sub-basin. The aim of the study was to determine the correlation between oil and source rock in terms of age, depositional environment, organic material sources, and maturity level. The total organic carbon content of the claystone samples varies from 0.03 to 4.52 wt%, which are classified as poor to excellent. The claystones are immature to post-mature with a mixture of Type II and III kerogen. Their vitrinite reflectance values range from 0.47 to 4.52 %Ro. The samples of Toraja Formation rock and the oil seep source rock might have a similar depositional environment, a deltaic marine depositional setting with high oxidizing conditions. Organic material sources for rock and oil samples are dominated by terrestrial input. The oil is inferred to have originated from the Paleogene source rocks, which correlates in age with the Toraja Formation. The recovered palynomorphs from the studied rock samples suggest a late Eocene to Oligocene age with a strong terrestrial influence of shallow marine depositional setting. The biomarker analysis shows that the rock samples have a more substantial contribution from the terrigenous higher plants, while the oil sample indicates a higher degree of marine influence. The maturity levels are also different between the oil (peak mature) and the analyzed rock samples (immature). It is inferred that the oil seep source rock is equivalent to the analyzed rock sample but more mature, having been deposited under more marine conditions. The oil seep source rock is not exposed and is located in the deeper part of the basin. A deeper marine facies (i.e. distal delta front and prodelta facies) in front of the distributary mouth bar within a delta is interpreted as the source rock of the oil seep sample. [ABSTRACT FROM AUTHOR]

The Paleogene coal deposits of the Jaintia Hills of Meghalaya have undergone examinations by various researchers, primarily focusing on organic petrography and geochemistry and highlighting the rank, type, and grade, with perspectives on potential utilization. However, the genesis of these coals has received limited attention from the researchers. This research article addresses this gap by conducting a comprehensive examination of the geochemical and mineralogical aspects of these coals. Coal samples from two coal seams at nine locations in the Sampar coalfield in Jaintia Hills were collected and studied. The samples are subjected to X-ray fluorescence spectroscopy, X-ray diffraction analyses, Fourier transform infrared spectroscopy, proximate, and ultimate analysis to study geochemical and mineralogical composition and ash yield. The study utilizes various geochemical proxies based on the inorganic constituents, providing insights into the paleo-depositional conditions and contributing to a deeper understanding of the unique characteristics of Meghalayan coals. The research indicates that these coals were formed in coastal swamps and lagoons on stable platforms, experiencing minimal tectonic activity, influenced by seawater incursions. These coals were deposited in reducing to significantly reducing conditions and warm and humid to semi-arid climatic conditions. No signature of a geothermally active fluid has been recorded. [ABSTRACT FROM AUTHOR]

Salinized lacustrine shale (SLS) represents a frontier in the global quest for unconventional hydrocarbon resources. The impact of terrigenous input, which includes terrigenous organic matter (OM) and detrital matter, on the deposition and hydrocarbon potential of SLS is still controversial. Here, we examine this issue using the newly discovered SLS within the Paleogene Biyang Depression, employing a combination of organic petrographic and geochemical analyses. A high influx of terrigenous input (terrigenous OM and detrital matter) promotes the formation of SLS. On the one hand, terrigenous higher plants emerge as the primary source of OM in the SLS, as indicated by the dominance of terrigenous macerals (e.g., terrigenous liptinite) and the abundance of plant-derived biomarkers (e.g., tricyclic terpanes). Additionally, a portion of the OM may originate from bacteria. On the other hand, the rapid input of detrital matter improves the preservation of OM, resulting in the deposition of SLS with high total organic carbon (TOC) contents and low hydrogen index (HI) values. The findings of this study contribute to a deeper understanding of SLS deposition and provide guidance for regional hydrocarbon exploration. [ABSTRACT FROM AUTHOR]

The exploration of continental shale oil in China has made a breakthrough in many basins, but the pure shale type has only been found in the Qingshankou Formation, Gulong Sag, Songliao Basin, and the evaluation of shale oil occurrence and sweet spot faces great challenges. Using information about the total organic carbon (TOC), Rock-Eval pyrolysis, vitrinite reflectance (Ro), kerogen elemental composition, carbon isotopes, gas chromatography (GC), bitumen extraction, and component separation, this paper systematically studies the organic geochemical characteristics and shale oil occurrence at the Qingshankou Formation. The G1 well, which was cored through the entire section of the Qingshankou Formation in the Gulong Sag, was the object of this study. On this basis, the favorable sweet spots for shale oil exploration are predicted. It is concluded that the shale of the Qingshankou Formation has high organic heterogeneity in terms of organic matter features. The TOC content of the source rocks in the Qingshankou Formation is enhanced with the increase in the burial depth, and the corresponding organic matter types gradually changed from Ⅱ2 and Ⅱ1 types to the Ⅰ type. The distribution of Ro ranges from 1.09% to 1.67%, and it is the mature to high-mature evolution stage that generates a large amount of normal crude oil and gas condensate. The high-quality source rocks of good to excellent grade are mainly distributed in the Qing 1 member and the lower part of the Qing 2 member. After the recovery of light hydrocarbons and the correction of pyrolytic heavy soluble hydrocarbons, it is concluded that the occurrence state of shale oil in the Qingshankou Formation is mainly the free-state form, with an average value of 6.9 mg/g, and there is four times as much free oil as adsorbed oil. The oil saturation index (OSI), mobile hydrocarbon content, Ro, and TOC were selected to establish the geochemical evaluation criteria for shale oil sweet spots in the Qingshankou Formation. The evaluation results show that interval 3 and interval 5 of the Qingshankou Formation in the G1 well are the most favorable sections for shale oil exploration. [ABSTRACT FROM AUTHOR]

The distribution of stable isotopes in organic compounds within geochemical systems reflects the reactions they undergo, which are often kinetically governed and can be elucidated through quantification based on first principles: employing quantum chemical simulations to derive energy barriers and kinetic isotope effects (KIEs), followed by kinetic calculations using these parameters. In this paper, the distribution of 13C in hydrocarbon gases during the thermal generation and decomposition of ethane and propane has been addressed. The work is based on abundant and systematic isotopic data, including the compound- and position-specific 13C compositions, recent improvements in kinetic networks in hydrocarbon generation, and state-of-the-art quantum chemical methods that can process organic geochemical systems involving solid phases. Density Functional Theory computations validate the carbonium path of hydrocarbon generation and the free-radical path of their decomposition under geological conditions. The first step of each path (alkyl sidechain protonation for generation and hydrogen abstraction for decomposition) is the rate-limiting step and determines the 13C fractionations of gaseous hydrocarbons, with the reaction rate constrained by the concentration or accessibility of the active species (hydrated protons and surface free radicals in the two paths, respectively). Alkyl protonation has normal 13C KIEs, but hydrogen abstraction on the surfaces of solid organic matter has inverse ones (substituting 12C by 13C accelerates the reaction). These inverse KIEs explain three isotopic phenomena in gaseous hydrocarbons in their late thermal evolution: 1) the depletion of 13C in ethane and propane accompanied by their decreased fraction in hydrocarbon gases (isotope "rollover"); 2) the reversed 13C sequence with carbon number (δ13C methane > δ13C ethane > δ13C propane); and 3) the depletion of 13C in the center carbon atoms of residual propane. Isotopic fractionation between gaseous hydrocarbons upon generation is evaluated using the Successive Random Chain-Scission model. The covariation of δ13C in alkanes shows a depletion in CH 4 compared with the values expected from the reciprocal of the carbon numbers, indicating that this deviation may be intrinsic instead of mixing with microbial methane. The comparison of intramolecular 13C fractionation of propane between computational and observed data suggests the contribution of isoprenoids at the beginning of the generation, in addition to isotopic homogenization between the center and end carbon atoms through the ring closure of intermediate cations. The 13C–13C clumping exhibits a weak KIE in both the generation and decomposition of ethane; the clumping is essentially stochastically governed. This work demonstrates how first-principle calculations can provide significant insights into the details of geochemical reactions governing the isotopic distributions. [ABSTRACT FROM AUTHOR]

Shelf seas are experiencing a rise in shallow gas leaks, primarily methane, raising concerns due to their environmental impact. However, the effect of the leaks on early diagenesis remains poorly understood. This study analyzes sediment lithology, organic geochemistry and porewater geochemistry of two short cores collected nearby the pockmarks in the muddy inner shelf of the East China Sea. Our findings clearly demonstrate the impact of methane leakage on early diagenesis, evidenced by the shallower position of the SMTZ (sulfate-methane transition zone), higher concentrations of uranium (U), vanadium (V), and manganese (Mn) in the porewater near and above the SMTZ, and downcore decrease in Mg2+, Ca2+, and Sr2+ concentrations versus increase in Mg2+/Ca2+ and Sr2+/Ca2+ ratios. Their profile variations and the difference between two cores are determined by the intensity of methane leakage. The estimated methane diffusive flux of 619 mmol m-2 yr-1 at YEC7-2 is roughly 8.5 times that at YEC7-1 (73 mmol m-2 yr-1), consistent with a shorter distance of YEC7-2 to the pockmark with active methane leakage. A schematic model is summarized to demonstrate the response of early diagenesis processes to the increasing methane leakages in response to changing sedimentation regimes from accretion to severe erosion. This study undoubtedly improves our understanding mutual promotion effect between seafloor erosion and gas leakage, and their impact on early diagenesis processes and resultant porewater geochemical changes and authigenic mineral records. [ABSTRACT FROM AUTHOR]

The Saltpond Basin, situated within the South Atlantic margin of Ghana, is a significant area for petroleum exploration but has received relatively limited research attention. Previous studies have examined source rock composition, but data on crude oil organic chemistry are lacking, hindering understanding of the basin's petroleum system and evolution. To address this gap, we analyzed biomarkers and stable carbon-isotope ratios in Saltpond Basin crude oil using gas chromatography–mass spectrometry and gas chromatography–isotope ratio mass spectrometry to elucidate organic matter source, depositional environment, and thermal maturity. Findings were compared with oils from the West African segment of the South Atlantic margin, namely the Tano Basin and the Niger Delta Basin, to identify potential correlations and gain insights into regional variations. Molecular and isotopic results unveiled a significant prevalence of organic matter derived from lower marine organisms. Patterns of organic matter deposition and preservation in Saltpond oil samples suggested a suboxic marine transitional environment, contradicting conventional understanding of terrestrial dominance in such settings. Moreover, the potential for degradation processes to obscure differentiation between terrestrial and marine organic matter origins underscores the complex nature of organic matter dynamics in transitional marine environments. Analysis of molecular thermal maturity indices suggested Saltpond oils were expelled from source rocks exhibiting thermal maturity at the early maturity stage. Correlation analysis unveiled genetic disparities among crude oils sourced from the Saltpond Basin and those from the Tano and Niger Delta Basin, primarily due to variations in source input and depositional environment conditions. Saltpond oil exhibits lower terrestrial organic input than Tano Basin's crude oils, which also have less terrestrial input than Niger Delta Basin crude oils. Additionally, its paleodepositional environment notably differs from oils in the Tano Basin (anoxic transitional marine-lacustrine settings) and the Niger Delta Basin (suboxic–oxic terrigenous deltaic or marine or lacustrine environments). Thermal maturity range of Saltpond oil is comparable to oils in the Tano Basin but lower than oils in the Niger Delta Basin. These findings provide valuable insights into petroleum generation history and unique organic geochemical characteristics within the Saltpond Basin, essential for exploration, production, and environmental management efforts in the region. Furthermore, correlation studies provide evidence that distinct biological, geological, and paleoenvironmental conditions shaped various oil types in the West African segment of the South Atlantic margin. [ABSTRACT FROM AUTHOR]

The paper considers how different maturity criteria reflect the overall degree of approach to the chemical equilibrium state of OM. The material for this study was OM from carbonate, siliceous–carbonate, carbonate–siliceous, and siliceous rocks of the northern and central regions of the Volga–Ural area (more than 100 samples). The raw data were processed using the apparatus of nonparametric correlation analysis (paired correlation coefficients between 27 parameters and partial correlation coefficients). The strengths of relations between maturity criteria based on reactions of different type (for example, reactions of C–C bond cleavage and isomerization reactions of aromatic compounds) were studied. It is shown that none of the 266 correlation coefficients corresponds to the values characteristic of a functional dependence. The partial correlation coefficients show that there are only thirteen pairs in which the parameters determined by reactions of different type are directly interrelated, and the strength of the relation significantly affects the values of both parameters. Thus, the values we measured in carbonate and silicite rocks cannot be to used to characterize the general approach of their OM to chemical equilibrium. Although the concept of "maturity" may have, technically speaking, the meaning of a general tendency toward equilibrium, it should be admitted that no methods are available so far to measure it. No data can be used to identify the only single parameter whose value is controlled only by the maturity value. Moreover, it is quite probable that there is no such a parameter at all. Nowadays the degree of approach to chemical equilibrium can be characterized only by using a set of parameters determined by reactions of all four types identified in the work. [ABSTRACT FROM AUTHOR]

The controlling factors of organic-rich shale accumulation is essential for the exploration and development of shale oil and gas resources. The sedimentary environment plays a vital role in the formation of organic-rich sediments in lacustrine facies. This article unravels the mineralogy, geochemistry, and paleoenvironmental evolution during the deposition of the Paleogene Shahejie Formation (Es3 L). It discusses the effects of paleoclimate, paleosalinity, paleoredox conditions, paleowater depth, and paleoproductivity on organic matter (OM) enrichment. Finally, the OM enrichment model was established. The results show that the mineralogical compositions are mainly composed of calcite (avg. 40.13%), quartz (avg. 21.64%) and clay minerals (avg. 24.07%), accompanied by dolomite (avg. 7.07%), feldspar (avg. 6.36%) and pyrite (avg. 2.95%). The Es3 L shale has a high abundance of OM, with total organic carbon (TOC) ranging from 1.07% to 5.12%. The organic matter type is mainly composed of type I-II1 kerogen, which is generally considered a good-quality source rock. The source of OM is a mixture of lower bacteria, algae, and plants. During the early sedimentary period, the paleoclimate was dry and cold, with high salinity, intense reducibility, and relatively low productivity. During the late sedimentary period, the climate became warmer and more humid. As a result, the salinity decreased to a level that was suitable for biological reproduction, and productivity increased gradually due to the input of terrigenous plants. Paleosalinity and paleoclimate determined the environment of the sedimentary period, in addition, paleoproductivity and paleoredox condition indicated the formation and preservation conditions of OM. The warm and humid climate, brackish water, suitable reduction conditions and high productivity are the favorable conditions for the generation and preservation of organic matter. The research results may have implications for the genetic mechanisms of organic matter accumulation. They will provide theoretical and technical insights into the exploration and development of shale oil. [ABSTRACT FROM AUTHOR]

The Upper Miocene–Pliocene Kampungbaru Formation crops out in the easternmost part of the Lower Kutai Basin, Indonesia. The sedimentological analysis of seven outcrops was carried out, and a total of twenty-five samples from these outcrops was analyzed for bulk geochemistry, organic petrography, and bulk and clay mineralogy to assess the effect of the climate and depositional environment on organic matter enrichment. The Kampungbaru Formation consists of interbedded sandstone, siltstone, claystone, and thick coal beds, which were classified into eleven lithofacies. Subsequently, seven facies associations were identified, namely the fluvial-dominated distributary channel, sheet-like sandstone, tide-influenced distributary channel, mouth bar, crevasse splay, delta plain, and delta front. The coal facies generally have a high amount of total organic carbon (TOC, 5.1–16.9; avg. 10.11 wt.%), and non-coal layers range from 0.03 to 4.22 wt.% (avg. 1.54 wt.%). The dominant maceral is vitrinite, while liptinite occurs only rarely in the samples. Organic matter is inferred to have originated from terrestrial plants growing in mangrove swamps. Identified clay minerals include varying proportions of kaolinite, illite, chlorite, and mixed layer illite/smectite (I/S). Kaolinite, which commonly constitutes up to 30% of the clay volume, indicates intensive chemical weathering during a warm and humid climate. In accordance with the Köppen climate classification, the paleoclimate during the deposition of the Kampungbaru Formation is classified as type Af, which is a tropical rainforest. Tropical climate was favorable for the growth of higher plants and deposition of organic matter under anoxic conditions and led to higher amounts of TOC in the Kampungbaru Formation. [ABSTRACT FROM AUTHOR]

Understanding the behavior of mercury (Hg) in organic‐rich sediments as they undergo thermal maturation is important, for example, because enrichment of Hg in sedimentary deposits has become a widely used proxy for volcanism from Large Igneous Provinces (LIPs). In this study, we evaluate the effects of such processes on sedimentary Hg concentrations by investigating a common stratigraphic interval in three drill cores with different levels of thermal maturity (immature, mature and post‐mature) in Toarcian sediments (Posidonienschiefer Formation) from the Lower Saxony Basin, Germany. We present Hg concentrations, bulk organic geochemistry, and total sulfur data. Mercury concentrations in the mature and post‐mature sediments are increased >2‐fold relative to the immature material, which is greater than any potential differences in original Hg concentrations in the studied successions prior to burial. Organic‐carbon and host‐rock mass loss during thermal maturation may have concentrated Hg in the mature sediments to some extent, provided Hg is considered effectively immobile. The increased Hg, TOC‐normalized Hg, and TS‐normalized Hg are most likely linked to the "closed system" behavior of Hg in sedimentary basins and the relatively low temperatures (70–260°C) during maturation that resulted in limited Hg mobility. More speculatively, a certain degree of redistribution of Hg within the mature sediments is suggested by its enrichment in distinct stratigraphic levels. Regardless of the exact mechanisms at play, the elevated Hg concentrations in mature sediments amplify both Hg/TOC and Hg/TS, implying that thermal effects must be considered when using normalized Hg as a proxy for far‐field volcanic activity. Plain Language Summary: This study examines how mercury (Hg) behaves in organic‐rich sediments that undergo thermal maturation, which is crucial for using Hg concentrations as a proxy for paleo‐volcanic activity. We analyzed three drill cores from the Lower Saxony Basin in Germany, each representing different stages of thermal maturity (immature, mature, and post‐mature). We measured Hg concentrations, organic content, and sulfur levels in these sediments. We found that mature and post‐mature sediments show more than double the Hg concentrations compared to immature sediments. This increase is likely due to the loss of organic matter and rock mass during maturation, which concentrates the remaining Hg. The relatively low temperatures (70–260°C) during maturation kept Hg from moving significantly, resulting in higher concentrations in mature sediments. There might be some redistribution of Hg within mature sediments, seen as enrichment in certain layers. Overall, the study highlights that thermal maturation effects must be accounted for when using Hg as a proxy for paleo‐volcanic activity. Key Points: Hg concentrations in thermally matured organic‐rich deposits have increased >2‐foldHg mobilization and recapture may occur during thermal maturation, and may result in stratigraphic increases in Hg concentrationsThe thermal history of sediments must be considered when using Hg as a proxy for volcanism [ABSTRACT FROM AUTHOR]

Objective As a newly discovered source rock in the Fuman area of the Tarim Basin, the source rock of the Tumuxiuke Formation has good petroleum exploration prospects, and the geochemical evaluation of the source rock is conducive to guiding exploration. Methods The qualitative and quantitative characterization of drill cuttings from the Tumuxiuke Formation in the Fuman area was carried out by means of total organic carbon (TOC) content, Rock-Eval pyrolysis, and GC-MS analysis of saturated and aromatic hydrocarbons. Results The results show that the source rock of the Tumuxiuke Formation is a good to excellentsource rock, with an average TOC content of 3.4%. The highest hydrogen index (HI) is 590 mg/g, and the kerogen type is mainly type Ⅱ. According to the molecular geochemical characteristics, the source rock was formed in a marine sedimentary environment with weakly reducing brackish water, with aquatic algae as the primary hydrocarbon-generating organisms.Based on the peak temperature (Tmax) of Rock-Eval, saturated hydrocarbon biomarker compounds, and aromatic hydrocarbon thermal maturity parameters, the source rock of the Tumuxiuke Formation is generally in the mature-medium mature evolution stage and has good hydrocarbon generation potential. Conclusion As the sedimentary center of the Huanman Depression, the southern Fuman area may have thicker and higher-quality Tumuxiuke source rock with a greater degree of thermal evolution, whose contribution to the oil and gas resources in the Ordovician cannot be ignored.

The article considers the elements of organic geochemistry in the regional aspect, which aims to separate quantitative prediction of oil and gas content of regions. The principles and results of balance calculations of generation and emission of liquid and gaseous hydrocarbons for different faciesgenetic types of organic matter and methods for calculating the scale of hydrocarbon emission are considered. Finally, a list of the main regularities of organic geochemistry is given.

The origin of methane in hydrothermal fluids has long been a subject of debate – whether it is abiotic or biotic. In this study, we aim to unravel and quantify the sources of CH 4 in active hydrothermal systems by adopting a holistic approach analyzing well characterized high-temperature hydrothermal fluids (∼230–310 °C) in Iceland. We employ a broad variety of geochemical and isotope indicators, encompassing chemical and isotope compositions of the targeted fluids. These signatures are then compared with results from chemical and isotope kinetic models and data from sedimentary-hosted hydrothermal systems. Carbon species in these fluids include CO 2 (2.60–184 mmol/kg), CH 4 (2.39·10−4–0.325 mmol/kg), dissolved organic carbon (4.78·10−3–0.112 mmol/kg), and CO (1.89·10−6–4.16·10−4 mmol/kg). Carbon and helium isotopes suggest a relatively uniform mantle-derived source of CO 2 (δ13C-CO 2 : −4.80 to −1.50 ‰, CO 2 /3He: 1.49·109–4.14·1010 14C-CO 2 : 0.11–2.42 pMC). Methane, in contrast, has multiple sources. Overall, chemical equilibria among carbon species (CO 2 , CH 4 , CO) is not attained, suggesting kinetic controls. Tritium content (<0.8–1.42 TU) and hydrologic constraints indicate relatively short hydrothermal fluid residence times (∼5–200 years), with occasional inputs from older water components. Within this short timeframe, CH 4 concentrations vary from lower, to significantly higher than those calculated using CO 2 reduction kinetics. The isotope composition (δD-CH 4 : −172 to −138 ‰, δ13C-CH 4 : −32.0 to −24.6 ‰; 14C-CH 4 : 0.36–11.54 pMC) and geochemical and isotope modeling suggest that the majority (>80–90 %) of CH 4 originates from a radiocarbon inactive source, i.e. mantle CH 4 , reduction of mantle CO 2 and/or old organic matter, with relatively small contributions from both marine (<20 %) and terrestrial (<10 %) dissolved organic carbon. Measured isotopic compositions of CH 4 do not match those expected for mantle-derived CH 4 as well as values generated from reduction of mantle-derived CO 2. Instead, differences in δD-CH 4 and δ13C-CH 4 values exist between systems fed by meteoric water and those fed by seawater, challenging the assumption of a uniform CO 2 source and invariable reaction mechanisms. Differences between systems are best explained by variable extent of thermal decomposition and primary variations in the isotope composition of marine and terrestrial organic matter. Also, δD-CH 4 and δ13C-CH 4 values in meteoric water-fed systems closely resemble those in the Öxarfjördur sedimentary-hosted systems. In summary, our data supports a predominant thermogenic origin of CH 4 in both seawater and terrestrial hydrothermal fluids in Iceland. The source of organic matter appears to be a combination of modern dissolved organic carbon and older sedimentary deposits. In addition, some of the hydrothermal systems studied (Krafla, Reykjanes, Theistareykir) which are characterized by low CH 4 concentrations, may contain a significant portion of CH 4 that may originate from CO 2 reduction. [ABSTRACT FROM AUTHOR]

This contribution marks the achievements made in the past decades by a group of mainly Egyptian palynologists. The data generated covers a long-time span from the Precambrian to the Holocene of Egypt. Previously published results are devoted primarily to the study of many exploration wells and outcrop sections. Comprehensive studies were carried out on a range of palynomorph groups including spores and pollen, algae and prasinophytes, dinoflagellate cysts, acritarchs, scolecodonts, chitinozoans, and other miscellaneous forms as well as palynofacies. Particular attention is given to the history of palaeopalynology. This study has identified three main phases. The results of the first phase were limited, as the knowledge of palynology in Egypt was poorly known from 1959 until 1979. Between 1980 and 2000, which represents the second or shaping phase, an intensive study of surface and subsurface material was carried out. The third phase (2000 until now) provides the academic and commercial expansion of palynological research in Egypt, where palynology can have immediate application in petroleum exploration studies. In the first phase, the application of palynology was seriously hampered by the limited extent of the published data. Only 27 works emerged by the end of 1979. A considerable acceleration was noted in the second phase when palynological research was established in many national institutions and started to play a considerable role in petroleum exploration. Beyond academia, some of the operating oil companies started to set up palynological laboratories and staff as part of biostratigraphy teams. These included, for example, GPC, Khalda Petroleum Company with a focus on the north Western Desert, and GUPCO with a focus on the Gulf of Suez, and most of the results obtained were incorporated with the internal data on the well files. During the period 2000–2009, especially when palynofacies studies were incorporated, the progress and the direction of palynological research changed. This allowed for a more accurate reconstruction of the depositional process and eventually a palaeobiogeographical history mainly for the Cretaceous, which is an important target for hydrocarbon exploration in Egypt. From 2010 onwards, the number of publications has clearly grown and reached 23 publications in 2020. Such a high pace of development seems to have been at the expense of basic research comprising taxonomy and biostratigraphy, something that might negatively impact the quality of research and also researchers, especially early career researchers. The change brought about through this phase by integrating organic geochemistry, sedimentology, and other disciplines may, however, have left a positive impact, principally in terms of international collaborations and expansion of palynological applications beyond the standard academic cluster. Important highlights and outputs, and prospective forthcoming developments and recommendations pertaining to Egyptian palynology generally (and in each phase) are discussed. [ABSTRACT FROM AUTHOR]

The unclear understanding of the source rock characteristics for the Paleogene Dongying Formation in the Bozhong Sag leads to the lack of cognition in oil and gas exploration. This research systematically evaluated the discrepancy in geochemical characteristics of source rock intervals in the Dongying Formation based on detailed analysis using Rock‐Eval pyrolysis, total organic carbon (TOC), vitrinite reflectance (Ro), maceral components, stable carbon isotopes and biomarker parameters. It discusses the organic matter sources, depositional environment, thermal maturity and hydrocarbon generation potential in the source rock intervals of the Dongying Formation. The organic matter abundance in the third member (E3d3) and lower sub‐member of the second member (E3d2L) of the Dongying Formation is higher, with an average TOC of 2.08% and 1.03%, respectively, indicating that these source rock intervals could have good and excellent quality. The source rocks of the Dongying Formation predominately contain exinite maceral group and type II1 and II2 kerogen. The thermal evolution is mainly in the low‐mature and mature stages. The organic matter sources in the Dongying Formation are mainly dominated by mixed origin (the carbon isotope reversal of aromatics also provides a potential explanation). However, the values of 1,2,5−/1,3,6‐trimethylnaphthalene, (1,2,5,6 + 1,2,3,5)‐tetramethylnaphthalene/tetramethylnaphthalenes, methyldibenzofuran/methylphenanthrene (MDBF/MP) and dibenzofuran/phenanthrene (DBF/PHEN) parameters in the E3d3 and some samples in E3d2L decipher relatively smaller values than other source rock intervals, proving the enhancement of the contribution of lower organisms. Moreover, the terrestrial input in the bottom‐up deposition process of the Dongying Formation gradually increases. The depositional environment reveals the Dongying Formation source rocks mainly developed freshwater sulphur‐poor lacustrine facies and shallow lake‐fluvial delta facies in an open clay‐rich sedimentary environment with poor water column stratification, belonging to the typical weak oxidation–reduction depositional conditions. The comprehensive geochemical evaluation concludes that the favourable supply of lower organisms and stable clay‐rich depositional environment in the E3d3 interval of the Dongying Formation are potential explanations for the formation of lacustrine source rocks with high organic matter abundance, intermediate thermal evolution and excellent hydrocarbon generation potential, providing a good foundation for the exploration and development prospects of hydrocarbons. [ABSTRACT FROM AUTHOR]

Gas chromatography-mass spectrometry (GC-MS) is an extremely important analytical technique that is widely used in organic geochemistry. It is the only approach to capture biomarker features of organic matter and provides the key evidence for oil-source correlation and thermal maturity determination. However, the conventional way of processing and interpreting the mass chromatogram is both timeconsuming and labor-intensive, which increases the research cost and restrains extensive applications of this method. To overcome this limitation, a correlation model is developed based on the convolution neural network (CNN) to link the mass chromatogram and biomarker features of samples from the Triassic Yanchang Formation, Ordos Basin, China. In this way, the mass chromatogram can be automatically interpreted. This research first performs dimensionality reduction for 15 biomarker parameters via the factor analysis and then quantifies the biomarker features using two indexes (i.e. MI and PMI) that represent the organic matter thermal maturity and parent material type, respectively. Subsequently, training, interpretation, and validation are performed multiple times using different CNN models to optimize the model structure and hyper-parameter setting, with the mass chromatogram used as the input and the obtained MI and PMI values for supervision (label). The optimized model presents high accuracy in automatically interpreting the mass chromatogram, with R² values typically above 0.85 and 0.80 for the thermal maturity and parent material interpretation results, respectively. The significance of this research is twofold: (i) developing an efficient technique for geochemical research; (ii) more importantly, demonstrating the potential of artificial intelligence in organic geochemistry and providing vital references for future related studies. [ABSTRACT FROM AUTHOR]

Sediment source fingerprinting using biomarker properties has led to new insights in our understanding of land use contributions to time-integrated suspended sediment samples at catchment scale. A time-integrated mass-flux sampler (TIMS; also known as the 'Phillips' sampler), a cost-effective approach for suspended sediment collection in situ. Such samplers are widely being used to collect sediment samples for source fingerprinting purposes, including studies using biomarkers as opposed to more conventional tracer properties. Here, we assessed the performance of TIMS for collecting representative sediment samples for biomarkers during high discharge events in a small lowland grassland-dominated catchment. Concentrations of long odd-chain n-alkanes (> C23) and both saturated free and bound fatty acids (C14-C32), as well as compound-specific 13C were compared between sediment collected by both TIMS and autosamplers (ISCO). The results showed that concentrations of alkanes, free fatty acids, and bound fatty acids are consistently comparable between TIMS and ISCO suspended sediment samples. Similarly, compound-specific 13C signals were not found to be significantly different in the suspended sediment samples collected using the different samplers. However, different magnitudes of resemblance in biomarker concentrations and compositions between the samples collected using the two sediment collection methods were confirmed by overlapping index and symmetric coordinates-based correlation analysis. Here, the difference is attributed to the contrasting temporal basis of TIMS (time-integrated) vs. ISCO (discrete) samples, as well as potential differences in the particle sizes collected by these different sediment sampling methods. Nevertheless, our findings suggest that TIMS can be used to generate representative biomarker data for suspended sediment samples collected during high discharge events. [ABSTRACT FROM AUTHOR]

Reservoir characteristics and source rock geochemistry are essential for petroleum system investigation as they reveal reservoir quality and hydrocarbon generation capability, respectively. The primary Karama oil field reservoir of Abu El Gharadig Basin is the limestone-sand-shale Abu Roash G (AR/G) Member. This study examines AR/G, analyzes source rocks for maturity and organic elements, and defines the main reservoir lithotypes and evaluates reservoir properties. Five well log datasets and an AR/F pyrolysis analysis on another well were used in this study to characterize the AR/G's 168-foot effective thickness and assess the AR/F source-rock maturation. The effective porosity is up to 30%. The highest shale concentration was 24% in central and western parts of the field. Therefore, drilling development wells in this area, especially east and north, demands caution. The composition and vertical and lateral lithofacies variations of the defined reservoir in the Karama field region are a significant control of its petrophysical properties. The pyrolysis of AR/F revealed 1.32–5.84% content of organic matter. That content qualifies AR/F as a hydrocarbon source if thermal maturity is reached. Type I and type II kerogen in the Abu Roash F Member suggests oil production. The Abu Roash G Member and Upper Bahariya (UB) formation produce oil and gas due to their own type II and III kerogen. GC biomarker data suggests that the research area is predominantly maritime, with most samples showing environmental degradation. The area under consideration has one reservoir, AR/G, and three members of source rocks in AR/F&G and UB. AR/G electrofacies revealed various lithotypes and flow units. [ABSTRACT FROM AUTHOR]

The Lower Cambrian Niutitang Formation in the Northern Guizhou harbors abundant organic-rich mud shale, constituting the most significant marine shale gas reservoir in Guizhou. In this article, the reservoir characteristics of Lower Cambrian Niutitang Formation in Northern Guizhou are analyzed in terms of lithology, mineralogy, organic geochemistry, pore structure, gas content and continuous thickness of shale, and the exploration potential of shale gas in this area is evaluated. The results indicate that the content of brittle minerals in the shale of well QX1 is 65.29% to 95.22% (average of 82.10%). The total organic carbon (TOC) content ranges from 2.06% to 12.10% (average of 5.64%). The organic matter maturity (Ro) within the range of 2.29–2.67%, and the kerogen type is identified as type I. The shale samples from the Niutitang Formation have high TOC content, suitable thermal maturity, and a favorable kerogen type, suggesting good gas generation potential. The results of scanning electron microscopy (SEM) show that intergranular pores, intragranular pores and microfractures are developed in the shale of well QX1, which can provide sufficient storage space for shale gas. The shale exhibits a continuous thickness of 105.66 m in the QX1 well, comprising a gas-bearing interval of 32.89 m at the top (with an effective continuous thickness of 18 m) and a hydrocarbon source rock layer of 75.78 m at the bottom. In comparison with other shale gas regions, Niutitang Formation shale in Northern Guizhou exhibits characteristics such as favorable gas generation conditions, greater storage conditions, excellent gas-bearing, strong frackability, and substantial continuous thickness, it has greater potential for shale gas exploration. [ABSTRACT FROM AUTHOR]

The aim of this work is to examine the levels, distribution, bases, and hazards of n-alkanes (n-C9 to n-C20) and PAHs in the seawater and sediments around oil production locations in the whole delta region. The variations in the levels of PAHs and n-alkanes in seawater and sediment of the Nile delta coast of the Mediterranean were investigated using GC–MS/MS. The Σn-alkanes residues ranged between 12.05 and 93.51 mg/L (mean: 50.45 ± 17.49 mg/L) and 4.70 to 84.03 µg/g (mean: 31.02 ± 27.995 µg/g) in seawater and sediments, respectively. Total PAHs concentrations ranged between 4.485 and 16.337 μg/L (average: 9.47 ± 3.69 μg/L) and 1.32 to 28.38 ng/g (average 8.61 ± 7.57 ng/g) in seawater and sediment samples, respectively. The CPI (carbon preference index) values fluctuated between 0.62 and 1.72 (seawater) and from 0.234 to 2.175 (sediment), proposing the variation sources of n-alkane in the studied area. PAHs concentrations were lower than the Effective Range Low (ERL) and Effective Range Median (ERM) levels. The Toxic Equivalent Quotient (TEQ) values oscillated between 0.002 and 6.84 ng/L and from 3.72 to 13.48 ng/g for the seawater and sediment samples, respectively. The Ant/(Ant + Phe) ratio in sediment and seawater samples indicated a pyrolytic source while the BaA/(BaA + Chry) ratio indicates petrogenic sources in most of the studied stations. [ABSTRACT FROM AUTHOR]

Stable carbon isotope ratios (δ13C values) of marine carbonates are widely used to infer the relative burial rates of organic carbon, a source of oxygen to the ocean‐atmosphere system. This inference, however, is based on the assumption that ocean‐atmospheric carbon is buried either as organic carbon or as marine carbonate minerals. The burial of authigenic carbonate minerals formed within sediments after deposition, with low δ13C values (i.e., similar to organic carbon), has been proposed to explain high δ13C values in marine carbonates without the need for high burial fluxes of organic carbon. To test this hypothesis, we focus on the Late Devonian, a time period with both pervasive ocean anoxia and a severe reduction in shallow‐water carbonate deposition—conditions hypothesized to promote authigenic carbonate formation. We present sedimentological and geochemical data from limestones and black shales of the Wabamun Group, Besa River and Exshaw formations of the Western Canada Sedimentary Basin. These data are compared to inorganic and organic weight percent measurements of North American shales acquired from the USGS National Geochemical Database (N = 4,437). Results show that basinal shale lack authigenic carbonate with low δ13C values and that the mean δ13C value of carbonate in these shales (−0.3‰) do not differ substantially from mean δ13C of carbonates in platform carbonates of a similar age (0.4‰). Furthermore, inorganic carbon content in Late Devonian shales (mean weight percent = 0.55%, N = 54) is lower than average Phanerozoic North American shale (mean of 1.95%, N = 4,055). Lastly, organic carbon‐to‐inorganic carbon ratios (OC:IC) of North American shales are well above 1 (mean = 3.72 for Late Devonian shales (N = 374), 2.25 for shales (N = 3,653) of all other ages). Therefore, even if the burial of fine‐grained siliciclastic formations carrying authigenic carbonates were to increase, the concomitant increase in organic carbon burial would be even larger. Together, data from this study do not provide evidence that the burial of authigenic carbonate would have a significant effect on global carbon isotope mass balance. Plain Language Summary: Stable carbon isotope ratios (δ13C) of marine carbonate rocks are widely used as a proxy for estimating the relative amount of organic carbon buried throughout geological time. Certain instances in the geologic record indicate pronounced δ13C excursions for which there is no corroborating evidence for enhanced organic carbon burial. It has been proposed that these excursions may be the result of high burial rates of authigenic carbonate—carbonate minerals formed in situ within marine sediments. We test this hypothesis by analyzing the stable carbon isotope composition of Late Devonian limestones and shales of the Western Canada Sedimentary Basin. We also compare the organic and inorganic carbon compositions of shales from this field study with those from the USGS Geochemical database, an archive of North American shale geochemistry data from across the Phanerozoic. Results show that carbonates found in Devonian shales do not have low average δ13C values, and average organic carbon content was shown to be significantly higher than inorganic carbon in shale samples across the Phanerozoic. These results signify that authigenic carbonate burial had a negligible effect on the global carbon cycle, and furthermore, an increase in shale burial would result in a higher increase in organic carbon compared to authigenic carbonate. Key Points: CaCO3 found in Late Devonian shales has average carbon isotope values similar to Late Devonian shallow marine carbonatesWeight percent values of inorganic carbon content in Late Devonian shales are low compared to average North American shaleThe mass ratio of organic to inorganic carbon in Late Devonian shales is much higher than average North American shale [ABSTRACT FROM AUTHOR]

The Eocene biota from the pre-rifting stage of the Upper Rhine Graben (southwest Germany) is, with exception of the world-famous fossil sites Messel and Bouxwiller, poorly known. While from these localities exclusively terrestrial and freshwater fossils were recovered, here we present floral and faunal assemblages from the middle Upper Rhine Graben which clearly indicate a temporarily brackish water environment and consist of a diverse palynomorph association, calcareous nannoplankton, foraminifers, ostracods and some fish and reptile remains. Based on the occurrence of Trochastrites hohnensis, a Lutetian age is assumed. Organic-walled dinoflagellate cysts, in particular Phthanoperidinium comatum, Phthanoperidinium echinatum, Apectodinium homomorphum and Apectodinium quinquelatum, suggest a late Ypresian to Lutetian age. The pollen and spores assemblage includes typical mid Eocene species, such as Tegumentisporis villosoides, Tricolporopollenites crassostriatus and representatives of Bombacaceae, but a late Ypresian to Priabonian age cannot be excluded. Foraminifers and ostracods do not further refine the biostratigraphical assignment. Hence, a Lutetian age is most probable. The mass occurrence of Neocyprideis, various foraminifer taxa and an organic-walled dinoflagellate cyst assemblage of very low diversity are indicative of a brackish water environment. Disarticulated vertebrate remains include fish teeth of Lepisosteidae, turtle plates and alligatoroid teeth of Diplocynodon and Hassiacosuchus. The present palaeogeographical scenarios do not consider a connection from the Upper Rhine Graben to the North Sea Basin, Alpine Sea/Paratethys or Paris Basin during the mid Eocene. Provided that the middle Upper Rhine Graben was land-locked and definitely not reached by a marine ingression during this time interval, we tentatively suggest that the brackish water taxa may have been accidentally introduced into a brackish inland sea by wind (anemochory), rain, highly mobile insects or vertebrates such as fish, birds and mammals (endozoochory/ectozoochory). The presumably freshwater calcareous nannoplankton species Nannoserratolithus minutus Martini is newly described. [ABSTRACT FROM AUTHOR]

An organic geochemical, petrographical, and palynological evaluation was conducted on 30 claystone outcrop samples of the Toraja Formation, along with a geochemical analysis of an oil seep in the Enrekang Sub-basin. The aim of the study was to determine the correlation between oil and source rock in terms of age, depositional environment, organic material sources, and maturity level. The total organic carbon content of the claystone samples varies from 0.03 to 4.52 wt%, which are classified as poor to excellent. The claystones are immature to post-mature with a mixture of Type Ⅱ and Ⅲ kerogen. Their vitrinite reflectance values range from 0.47 to 4.52 %Ro. The samples of Toraja Formation rock and the oil seep source rock might have a similar depositional environment, a deltaic marine depositional setting with high oxidizing conditions. Organic material sources for rock and oil samples are dominated by terrestrial input. The oil is inferred to have originated from the Paleogene source rocks, which correlates in age with the Toraja Formation. The recovered palynomorphs from the studied rock samples suggest a late Eocene to Oligocene age with a strong terrestrial influence of shallow marine depositional setting. The biomarker analysis shows that the rock samples have a more substantial contribution from the terrigenous higher plants, while the oil sample indicates a higher degree of marine influence. The maturity levels are also different between the oil (peak mature) and the analyzed rock samples (immature). It is inferred that the oil seep source rock is equivalent to the analyzed rock sample but more mature, having been deposited under more marine conditions. The oil seep source rock is not exposed and is located in the deeper part of the basin. A deeper marine facies (i.e. distal delta front and prodelta facies) in front of the distributary mouth bar within a delta is interpreted as the source rock of the oil seep sample.

The Oxfordian–Ryazanian was a period of widespread deposition of marine organic-rich mudstones in basins formed during the early phases of the rifting that heralded the formation of the present-day North Atlantic. Occasionally, uninterrupted deposition prevailed for 20 million years or more. Today, mudstones of this time interval are found on the shelves bordering the North Atlantic and adjacent areas from Siberia to the Netherlands. Here, we report data on two fully cored boreholes from Wollaston Forland (North-East Greenland, approx. 74° N), which represent an uninterrupted succession from the upper Kimmeridgian to the Hauterivian. The boreholes record basin development at two different positions within an evolving halfgraben, located at the margin of the main rift, and thus partially detached from it. Although the overall depositional environment remained an oxygen-restricted deep-shelf setting, rifting-related changes can be followed through the succession. The Kimmeridgian was a period of eustatic highstand and records the incipient rifting with a transgressive trend straddling the transition to the lower Volgian by a gradual change from deposits with high levels of total organic carbon (TOC) and kerogen rich in allochthonous organic matter to deposits with lower TOC and a higher proportion of autochthonous organic matter. This is followed by a slight regressive trend with lower TOC and increased proportions of allochthonous organic matter until rifting culminated in the middle Volgian–Ryazanian, indicated by increasing autochthonous organic matter and higher TOC, which prevailed until basin ventilation occurred towards the end of the Ryazanian. The properties of the reactive kerogen fraction remained rather stable irrespective of TOC, underlining the effect of terrigenous matter input for TOC. These variations are also captured by biological markers and stable carbon isotopes. The deposits are very similar to equivalent successions elsewhere in the proto-North Atlantic region, albeit the proportion of terrigenous kerogen is greater.

The study presents a multi-proxy archive from hypersaline coastal Lake Chokrak in eastern Crimea, a steppe region which is particularly susceptible to moisture fluctuations. XRF, organic carbon and nitrogen, and palynological analyses are used to reconstruct the evolution of the lake and landscape development around it and to provide information about the driving forces behind those changes, such as climate and human impact. The findings show that the basin was an open marine bay between 7640 and 5500 cal. yr BP. After 5500 cal. yr BP, the low rates of sea-level rise led to gradual infilling of the basin. The prevalence of mesic herb-grass steppe around the site, as well as the expansion of broad-leaved trees in the Crimean mountains, indicate relatively warm and humid climate conditions during the Mid-Holocene. Elemental proxies and marine NPPs point to a transition to lagoonal conditions from 4270 cal. yr BP. The progressive shallowing of the basin was accompanied by the spread of more xeric Artemisia -grass steppe, which suggests a shift to arid conditions. The occurrence of cereal pollen from 3660 cal. yr BP may indicate the first signs of cultivation in the study area. The active build-up of a sand barrier from 3000 cal. yr BP led to a gradual separation of the basin from the sea. By 900 cal. yr BP, the fully-formed sand barrier resulted in a transformation of the lagoon into a hypersaline lake. The closing of the lagoon was accompanied by an expansion of halophytic communities around the site. Human-induced vegetation changes became more pronounced with the development of agrarian and pastoral activities around the site from ca. 750 cal. yr BP. [ABSTRACT FROM AUTHOR]

Organic-rich shale rocks from the Paleocene–Eocene Palana Formation in western Rajasthan, India, were systematically investigated based on inorganic and organic geochemistry combined with microscopic examinations to evaluate the sedimentary paleoenvironmental conditions and volcanic activity and their impact on the high organic carbon accumulation. The Palana shales are categorized by high organic matter (OM) and sulfur contents, with total values up to 36.23 wt.% and 2.24 wt.%, respectively. The richness of phytoplankton algae (i.e., telalginite and lamalginite) together with redox-sensitive trace elements further suggests a marine setting and anoxic environmental conditions during the Paleocene–Eocene. The significant low oxygen conditions may contribute to enhancing the preservation of organic matter during deposition. The mineralogical and inorganic geochemical indicators demonstrate that the Palana organic-rich shale facies was accumulated in a warm and humid climate with moderate salinity stratification conditions in the water columns, thereby contributing to the high bioproductivity of the phytoplankton algae blooms within the photic zone. The presence of significant contents of zeolite derived from volcanic material together with silica minerals such as apophyllite and tridymite in most of the Palana organic-rich shales indicates a volcanic origin and supports hydrothermal activities during the Paleocene–Eocene period. These volcanic activities in this case are considered the influx of large masses of nutrients into the photic zone due to the ash accumulation, as indicated by the presence of the zeolites in the Palana shales. Therefore, the high bio-productivity associated with effective OM preservation led to the organic carbon accumulation in the Palana Formation during the Paleocene–Eocene. [ABSTRACT FROM AUTHOR]

The Fengcheng Formation is a crucial source rock and the primary reservoir for oil accumulation in the Mahu Sag. Crude oils are distributed throughout the Fengcheng Formation, ranging from the edge to the interior of the sag in the southern Mahu Sag. These crude oils originate from in-situ source rocks in shallowly buried areas and the inner deep sag. During migration, the crude oil from the inner deep sag affects the source rocks close to carrier beds, leading to changes in the organic geochemical characteristics of the source rocks. These changes might alter source rock evaluations and oil-source correlation. Based on data such as total organic carbon (TOC), Rock-Eval pyrolysis of source rocks, and gas chromatography-mass spectrometry (GC-MS) of the saturated fraction, and considering the geological characteristics of the study area, we define the identification characteristics of source rock affected by migrated hydrocarbons and establish the various patterns of influence that migrated hydrocarbons have on the source rock of the Fengcheng Formation in the southern Mahu Sag. The source rocks of the Fengcheng Formation are mostly fair to good, containing mainly Type II organic matter and being thermally mature enough to generate oil. Source rocks affected by migrated hydrocarbons exhibit relatively high hydrocarbon contents (S1/TOC > 110 mg HC/g TOC, Extract/TOC > 30 %, HC: hydrocarbon), relatively low Rock-Eval Tmax values, and relatively high tricyclic terpane contents with a descending and mountain-shaped distribution. Furthermore, biomarker composition parameters indicate a higher thermal maturity than in-situ source rocks. Through a comparison of the extract biomarker fingerprints of adjacent reservoirs and mudstones in different boreholes, three types of influence patterns of migrated hydrocarbons are identified: the edge-influence of thin sandstone-thick mudstone, the mixedinfluence of sandstone-mudstone interbedded, and the full-influence of thick sandstone-thin mudstone. This finding reminds us that the influence of migrated hydrocarbons must be considered when evaluating source rocks and conducting oil-source correlation. [ABSTRACT FROM AUTHOR]

Since the discovery of the vast Jimusaer shale oilfield in the southeastern Junggar Basin in 2012, there has been considerable interest in neighboring areas around Bogeda Mountain that have shale oil potential. The primary productive interval in the basin, the Middle Permian Lucaogou Formation (P2l), is well-developed in the areas of Qitai, Mulei, Shiqiantan, Chaiwopu, and Miquan. In this study, we conducted an assessment of the hydrocarbon generation potential of the P2l in these five areas and compared it with that of the P2l in the Jimusaer oilfield, which were determined by GC-MS, total organic carbon (TOC) and vitrinite reflectance (Ro) measurements, Rock-Eval pyrolysis, and organic petrology to investigate the type, origin, thermal maturity, hydrocarbon potential, and oil/gas proneness of organic matter in the P2l. Additionally, we applied open-system pyrolysis of hydrocarbon generation kinetics to explore differences in hydrocarbon generation and expulsion across various P2l mudstone/shale in the southeastern Junggar Basin. The findings of this study revealed that the P2l shale in Qitai and Miquan areas contains more abundant and lower thermally mature organic matter (early mature–mature stage), characterized by primarily Type II1–I kerogen, similar to that found in the P2l shale of the Jimusaer oilfield. Conversely, the P2l shale in Mulei, Shiqiantan, and Chaiwopu contains less abundant and more thermally mature organic matter (mainly mature–highly mature stage), dominated by Type II2–III kerogen. Consequently, shale in these areas is considerably less desirable for oil exploration compared to the Jimusaer shale. The semi-deep to deep lake facies in Miquan and Qitai exhibit the most promising exploration potential. This study can serve as a guide for shale oil exploration in the southeastern Junggar Basin. [ABSTRACT FROM AUTHOR]

The paleolake level, which is controlled by the moisture balance (precipitation minus evaporation) within the lake basin, is a significant factor in determining the deposition of lacustrine organic-rich shale (LORS) across geological time, and hence influences shale oil enrichment. However, the impact of lake-level-fluctuations on shale oil enrichment of LORS is not well understood. Based on an integration of bulk geochemistry, organic petrography, pyrolysis gas chromatography, and element compositions, we address this issue using the Paleogene Biyang Depression in East China as an example. High lake levels, combined with anoxic–suboxic conditions, brackish–saline water, high productivity, and low detrital influx, are favorable for LORS deposition, which is characterized by a large distribution area and thickness, a high potential for oil generation and emplacement, and a high free shale oil content. In contrast, LORS deposited during low lake levels, with suboxic–dysoxic conditions, fresh–brackish water, low productivity, and high detrital influx, has a small distribution area and thickness, a low potential for oil generation and emplacement, and a low free shale oil content (a comparable maturity was present in all the studied LORS). Our data suggests that the elevated lake level led to higher salinity, stronger reduction conditions, higher productivity, and lower clastic inflow in the paleolake, forming LORS with higher shale oil potential. It has a positive effect on shale oil enrichment of LORS. The findings are also applicable to regional shale oil exploration. [ABSTRACT FROM AUTHOR]