Marine and Petroleum Geology最新文献

{"title":"Developmental model and filling response characteristics of paleokarst conduits in the Middle-Lower Ordovician strata of Well 094 area, Tahe Oilfield","authors":"Jiyuan Gao ,&nbsp;Nuoyu Wang ,&nbsp;Heng Zhang ,&nbsp;Zhongxian Cai","doi":"10.1016/j.marpetgeo.2025.107596","DOIUrl":"10.1016/j.marpetgeo.2025.107596","url":null,"abstract":"<div><div>The Ordovician strata in the Tahe Oilfield of the Akekule Low Uplift, Tarim Basin, host diverse palaeokarst fracture–cavity reservoirs. Among these reservoirs, the large-scale epignic karst conduit system that formed during the early Hercynian represents one of the most significant reservoir spaces. The Well 094 well block, located in the Carboniferous-covered western slope area of the Tahe Oilfield, contains typical Ordovician palaeokarst conduit-type reservoirs. On the basis of 3D seismic and well logging data, in this study, the palaeokarst hydrogeomorphic conditions of the Ordovician strata in this area are reconstructed; the spatial distribution, developmental conditions, and filling characteristics of large-scale branchwork karst conduits are analysed; and their controlling factors are investigated. The results indicate that the Ordovician strata in the Well 094 well block were situated in the early Hercynian karstification zone, characterized by a typical binary flow field structure of a karst watershed. The karst landform exhibits medium-to-high relief, with well-developed asymmetrical branchwork surface drainage systems converging from north to south into a karst canyon. The karst conduits are predominantly developed approximately 120 ms below the top of the Lower-Middle Ordovician series. The development of these conduits was jointly controlled by the steep topographic gradient of the Ordovician strata, the syncline-confined groundwater convergence zone between secondary anticlines, and the water-conducting effects of NNE- and NNW-trending strike-slip faults. The karst conduits display distinct east‒west differential evolution. The eastern conduits experienced intense vertical erosion and roof collapse, forming a subsurface fluvial window geomorphology with severe clastic infilling, whereas the western conduits maintained relatively stable configurations. This finding suggests that conduit evolution is influenced by tectonic uplift and the hydraulic gradient, with the degree of infilling closely related to the watershed area, fault activity, and evolutionary stage. Highly evolved conduit segments tend to exhibit more severe infilling.The complete filling of the cave not only reduces porosity but also significantly compromises the reservoir's effective storage capacity. These findings provide a theoretical basis for evaluating the effectiveness of similar karst fracture–cavity reservoirs worldwide.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107596"},"PeriodicalIF":3.6,"publicationDate":"2025-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145044509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sedimentary characteristics and fault-controlled depositional models of gravity flows in the Eocene Shahejie formation, Bohai Bay Basin, China: Insights for hydrocarbon exploration in rifted lacustrine basins","authors":"Jie Geng ,&nbsp;Renchao Yang ,&nbsp;Aiping Fan ,&nbsp;Nils Lenhardt ,&nbsp;Liang Dong ,&nbsp;Yang Li","doi":"10.1016/j.marpetgeo.2025.107601","DOIUrl":"10.1016/j.marpetgeo.2025.107601","url":null,"abstract":"<div><div>Sediment gravity flows are critical sediment transport mechanisms in deepwater environments and play a key role in hydrocarbon accumulation. The well-developed sediment gravity flow deposits of the Shahejie Formation are major oil-bearing units in the Dongying Depression (Bohai Bay Basin, eastern China), yet the types of sediment gravity flow deposits and their controlling factors remain debated. This study introduces a novel step-fault-controlled framework in the lower section of the third member of the Eocene Shahejie Formation (ES3L sub-member) that goes beyond traditional models by highlighting the finer-scale structural influences on sediment distribution. The research discusses sedimentary characteristics, lithofacies types, facies distribution, and depositional models based on core samples, well logs, and seismic data from the relay ramp of the Dongying Depression, offering important insights for hydrocarbon exploration strategies. The results indicate that the sediment gravity flows responsible for the deposition in the study area were mainly sandy debris flows, turbidity currents, and hyperpycnal flows. Debrite sandstone deposits are characterised by numerous floating mud clasts, often associated with soft-sediment deformation structures. Turbidite sandstones are characterised by load casts and normal grading. Hyperpycnites are characterised by couplets of inverse grading and normal grading, periodic changes in grain size, and abundant plant debris. The development of sediment gravity flows within the study area was controlled by step faults. As a result, a step-fault-controlled sedimentary model of sediment gravity flow deposition was developed with the following characteristics: 1) Delta front deposition prevailed on the upper step fault, with minor deposition from gravity flows; 2) hybrid deposition of sandy debris flows and turbidity currents took precedence on the middle step fault; and 3) hyperpycnites dominated on the lower step fault. This study investigates the impact of stair-step faults on the sedimentary facies of gravity flows, providing guidance for oil and gas exploration and development in rifted lacustrine basins worldwide.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107601"},"PeriodicalIF":3.6,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145094965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mud volcanism and diapirism along the Japan Trench axis: evidence for a complex earthquake plumbing system on the down-going plate","authors":"Myra Keep ,&nbsp;Troy Rasbury ,&nbsp;Cecilia McHugh ,&nbsp;Michael Strasser ,&nbsp;Ken Ikehara ,&nbsp;Charlotte Pizer ,&nbsp;Yasuyuki Nakamura","doi":"10.1016/j.marpetgeo.2025.107597","DOIUrl":"10.1016/j.marpetgeo.2025.107597","url":null,"abstract":"<div><div>Mud volcanoes occur in a variety of geodynamic settings, and are common in subduction zones, usually within the accretionary prism. Although mud volcanism occurs along the Ryukyu Trench in southern Japan, no such activity has been documented along the Japan Trench. Sub-bottom profile data from International Ocean Discovery Program Expedition 386 show acoustically anomalous features in the basin-fill stratigraphy consistent with mud diapirism and mud volcanism along the Japan Trench. Unusually these features occur in basins along the trench axis itself, and not primarily as part of the accretionary complex. We present evidence for diapirism along ∼600 km of the Japan Trench and for mud volcanoes in the central and northern part of the trench. Mud diapirism and nearby igneous volcanic activity shows close spatial relationships to flexural faults on the down-going plate, which may provide the plumbing system for mobile muds to reach the surface.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107597"},"PeriodicalIF":3.6,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145026784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular migration tracers and basin modeling reconstruct the initial filling of the Ivar Aasen, Edvard Grieg, Solveig, and Johan Sverdrup fields of the Haugaland High, Norwegian North Sea","authors":"Thorsten Uwe Garlichs ,&nbsp;Lorenz Schwark","doi":"10.1016/j.marpetgeo.2025.107589","DOIUrl":"10.1016/j.marpetgeo.2025.107589","url":null,"abstract":"<div><div>An integration of geological, geochemical, and geophysical disciplines into a classical basin model is the key for a profound understanding of the migration and filling history of reservoirs in the Haugaland High, North Sea, as it delineates the generation, expulsion, and migration of hydrocarbons. The numerical basin model for migration assessment was tuned and calibrated with molecular geochemical data, especially by the application of benzocarbazole ratios as migration tracers and geochemical fingerprinting of oil families. Benzocarbazole distributions resolved the complex filling history and the initial filling directions of different migration sectors for the Haugaland High via their decreasing [a]/([a]+[c]) isomer ratios. These decline with increasing migration distance for different migration sectors extracted by a numerical basin model. The filling history was reconstructed as a complex multicharge system in a context of variable stages of paleobiodegradation. Hereby, benzocarbazole ratios obtained from oils and reservoir core extracts remained unaffected by biodegradation. They indicate an oil migration trend from the Viking Graben in the west of the Haugaland High towards the southeast, filling the present-day fields, e.g., Johan Sverdrup, Edvard Grieg, and Ivar Aasen. Benzocarbazole distributions represent the initial filling and do not show overprint effects by later and mature charges of oil lean in polar constituents. They thus exhibit a migration scenario in agreement with migration reconstruction via numerical basin modelling and previously proposed non-polar biomarker distributions.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107589"},"PeriodicalIF":3.6,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145044502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis and geological significance of pyrite in the Ordovician carbonate-evaporative strata of central Ordos Basin, China","authors":"Lianqi Jia ,&nbsp;Biao Qin ,&nbsp;Chenlu Ma ,&nbsp;Ruining Zheng ,&nbsp;Jie Zhang","doi":"10.1016/j.marpetgeo.2025.107586","DOIUrl":"10.1016/j.marpetgeo.2025.107586","url":null,"abstract":"<div><div>Deep burial carbonate-evaporative strata (4000–10000m) have significant exploration potential for gas-rich petroliferous basins. However, high temperature and thermal evolution destroy most hydrocarbon related organic geochemical parameters used to analyze the alteration of oil and gas reservoirs. This study is the first systematic attempt to assess hydrocarbon alteration and cracking based on generational evolution and geochemistry of pyrite. Pyrites in the subsalt carbonate of Ordovician Majiagou Formation of central Ordos Basin are formed in four stages (Py1, Py2, Py3 and Py4). The mineral morphology and geochemical characteristics indicate that Py1 was formed from microbial sulfate reduction. Py2, Py3 and Py4 are derived from thermochemical sulfate reduction (TSR). This is supported by coexistence between pyrite and other TSR products (calcite, bitumen and elemental sulfur), reaction condition and rich TSR reactants (hydrocarbon and sulfate). TSR occurs in a closed system, proved by increasing δ³⁴S values from Py2 to Py4 (6.2 ‰–73.9 ‰) and unusually high δ³⁴S values of residual vein anhydrite (36.2 ‰–44.8 ‰) in the reservoir. TSR pyrites (Py2, Py3 and Py4) have relatively high concentrations of transition metal elements, which is consistent with worldwide oil. Significantly decreasing trace element concentrations from Py2 to Py4 and from core to rim are attributed to TSR reactant transformation from oil to wet gas. Py2, Py3 and Py4 probably correspond to oil-dominated TSR, TSR-induced oil cracking and wet gas-dominated TSR respectively. Therefore, TSR pyrite is a potentially effective mineral to the evolution of deep burial gas reservoirs.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107586"},"PeriodicalIF":3.6,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145044504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chronological and geochemical constraints on the origin and timing of carbonate-cemented sandstones in the Middle Jurassic Zhiluo Formation, northeastern Ordos Basin, China","authors":"Yang Qin ,&nbsp;Chiyang Liu ,&nbsp;Junfeng Zhao ,&nbsp;Yanping Ma ,&nbsp;Lihua Yang ,&nbsp;Nan Du","doi":"10.1016/j.marpetgeo.2025.107595","DOIUrl":"10.1016/j.marpetgeo.2025.107595","url":null,"abstract":"<div><div>The northeastern Ordos Basin experiences significant natural gas dissipation. As key geological archives for deciphering hydrocarbon migration-dissipation processes, the genesis and timing of carbonate-cemented sandstones (CCSs) from the Zhiluo Formation (northeastern Ordos Basin) remain controversial and lack systematic investigation. In this study, we conducted a comprehensive investigation of CCSs, integrating petrographic characterization, in situ rare earth element (REE) and U-Pb geochronological analyses, coupled with C-O-Sr isotope and fluid inclusion studies. The CCSs represent non-syndepositional diagenetic products with three stages: Calcite 1 (147.4–125 Ma), Calcite 2 (119.78–100.9 Ma), and Calcite 3 (71.84–61.9 Ma). Calcite crystallinity progressively increases from Calcite 1 to 3, with distinct geochemical signatures across stages. The Calcite 1 generation predominantly originated from chemical precipitation during supergenic diagenesis, with diagenetic fluids dominated by alkaline-enriched external surface water. The formation of Calcite 2–3 was controlled by the amalgamation of deep-sourced hydrothermal fluids and hydrocarbon migration-dissipation. Notably, Calcite 2 also records superimposed supergene alteration involving terrigenous inputs, which serves as an intermediate diagenetic product. Hydrocarbon inclusions, which are ubiquitously hosted within Calcites 2–3, exhibit high thermal maturity, and the gas within inclusions has genetic affinity with Upper Paleozoic coal-derived natural gases from the Hangjinqi-Sulige field. This genetic linkage directly and compellingly indicates that Upper Paleozoic gas migration-dissipation served as the predominant light carbon source for Calcites 2–3 precipitation. The onset of Upper Paleozoic gas migration-dissipation occurred during the late Early Cretaceous, which may have persisted until present. Approximately 44.66 % of the organic-derived calcite proportion provides conclusive evidence for large-scale gas migration-dissipation.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107595"},"PeriodicalIF":3.6,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145044503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geological and geochemical approach to natural hydrogen exploration in the Northern Apennines, Italy","authors":"Vivian Azor de Freitas ,&nbsp;Alessandra Montanini ,&nbsp;Isabelle Moretti ,&nbsp;Andrea Artoni ,&nbsp;Stefano Segadelli ,&nbsp;Jean de la Paix Izerumugaba ,&nbsp;Anne Battani ,&nbsp;Giuseppe Etiope","doi":"10.1016/j.marpetgeo.2025.107594","DOIUrl":"10.1016/j.marpetgeo.2025.107594","url":null,"abstract":"<div><div>The western sector of Northern Apennines, Italy, presents favorable conditions for the occurrence of natural hydrogen (H₂), hosting ophiolitic bodies, hyperalkaline waters, and deep-seated faults. A geological and geochemical investigation was conducted to evaluate the potential for subsurface H₂ accumulations. The study involved gas analyses from spring waters, bubbling gas, and soil-gas measurements, along with petrographic analyses of ultramafic rocks. Multiple springs contain dissolved H₂ at low (up to 1 μM) to moderate (1 μM–100 μM) concentrations relative to other springs in serpentinized peridotites worldwide. In the Taro Valley, H₂ occurrences (0.28 μM–0.79 μM) are associated with hyperalkaline springs in proximity to exposed peridotites. However, the limited thickness of the peridotite body at Mt. Prinzera (∼250 m) suggests that the hyperalkaline water and associated H₂ likely derive from deeper unexposed ultramafic units. Petrographic analyses of spinel-peridotites reveal varying degrees of serpentinization (45 %–95 %), characterized by serpentine mesh textures with olivine relics, pyroxene converted into serpentine, and formation of magnetite and chromite. In the Bobbio Tectonic Window, springs with neutral pH waters, located away from exposed ultramafic bodies, contain higher concentrations of dissolved H₂ (0.49 μM–3.8 μM). Although the origin of this H₂ remains unclear, it may be related to hidden ultramafic bodies within the sedimentary sequence undergoing serpentinization. Notably, all the spring-related H₂ occurrences are associated with methane (CH₄), showing thermogenic isotopic signatures (<em>δ</em>¹³C: 58.3 ‰ to −35 ‰ and <em>δ</em>²H: 200 ‰ to −145 ‰). Further research should focus on the characterization of regional hydrocarbon reservoirs, which could also host natural H₂.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107594"},"PeriodicalIF":3.6,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145018400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geological characteristics and in-situ retention mechanisms of clay-rich lacustrine shale oil in the Songliao Basin","authors":"Min Wang ,&nbsp;Yan Wu ,&nbsp;Xuefeng Bai ,&nbsp;Ming Li ,&nbsp;Junhui Li ,&nbsp;Xin Wang ,&nbsp;Jinyou Zhang ,&nbsp;Jinbu Li ,&nbsp;Changqi Yu ,&nbsp;Roufeida Bennani","doi":"10.1016/j.marpetgeo.2025.107593","DOIUrl":"10.1016/j.marpetgeo.2025.107593","url":null,"abstract":"<div><div>The Cretaceous Qingshankou Formation in the Gulong Sag of the Songliao Basin, located in the eastern of the Eurasian Plate, exhibits unique shale oil properties, including high clay mineral content (&gt;40 %), high organic matter maturity (&gt;1.0 %), and low shale oil density (∼0.78 cm³/g). This represents the first globally documented shale oil produced from clay-rich shales. This study systematically investigates the characteristics and controlling factors of reservoir space, oil-bearing properties and the formation and enrichment processes of shale oil. Findings reveal that the Qing-1 Member predominantly comprises laminated argillaceous shale, bedded mixed shale, and massive calcareous shale. The kerogen is mainly Type I, characterized by well-developed lamalginite and high organic matter (OM) abundance, with an average Total Organic Carbon (TOC) of 2.27 %. Thermal maturity (R_o) in oil-producing intervals typically exceeds 1.0 %. The main pore types are intergranular pores, intragranular pores, OM-hosted pores, exposed pores after OM degradation, and microfractures, with pore development influenced by TOC, clay mineral content, and R_o. The Gulong shale is notably oil-rich, with oil films present observed in different types and sizes of pores, and oil content significantly affected by TOC and R_o. The coupling of hydrocarbon evolution, fault activity periods, and regional stress changes governs the in-situ retention of light oil within the sag and dictates the reservoir formation sequence and spatial distribution of tight and conventional oil outside the source rock. This study offers critical insights for the exploration and development of continental clay-rich shale oil reservoirs.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107593"},"PeriodicalIF":3.6,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144921642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanisms for initiation and termination of extraordinarily high total organic carbon in the Longmaxi Formation, Yangtze Platform, South China","authors":"Zongyuan Sun ,&nbsp;Hao Chen ,&nbsp;Xianguo Lang ,&nbsp;Bolin Zhang ,&nbsp;Qing Chen ,&nbsp;Kun Zhao ,&nbsp;Shengxian Zhu ,&nbsp;Fangqi Zhao ,&nbsp;Feng Liang ,&nbsp;Chuyuan Liu ,&nbsp;Junxuan Fan","doi":"10.1016/j.marpetgeo.2025.107588","DOIUrl":"10.1016/j.marpetgeo.2025.107588","url":null,"abstract":"<div><div>The Early Silurian Longmaxi Formation in the Yangtze Platform of South China hosts exceptional shale gas reservoirs, particularly in intervals where total organic carbon (TOC) exceeds 3 wt%. However, the initial TOC values and termination timing of these “extraordinarily high TOC” intervals differ markedly among localities, especially between inner- and outer-shelf settings. In this study, we integrate graptolite biostratigraphy, carbon isotope chemostratigraphy, and multiple geochemical proxies (e.g., major–trace elements and sulfur isotopes) from drill cores in Yichang, Hubei Province, South China (outer shelf). We establish a refined chronostratigraphic framework, identifying an extraordinarily high TOC interval (&gt;3 wt%) and a subsequent high TOC interval (2–3 wt%), and then compare these intervals with representative inner-shelf sections. Our results show that at the base of the Longmaxi Formation in Yichang, TOC values are notably lower than those in the inner-shelf Changning area, Sichuan Province, South China, whereas the extraordinarily high TOC interval extends to a higher stratigraphic level in Yichang. Paleoenvironmental proxies indicate that extraordinarily high TOC intervals formed in a euxinic setting with higher primary productivity, and moderate restriction, whereas the high TOC interval reflects an anoxic setting, lower productivity, and stronger restriction. By determining sedimentation rates, sulfur isotope values, paleogeographic setting, and the influence of the Kwangsian Orogeny, we propose two sedimentary models to explain TOC variability in the Longmaxi Formation. The Sedimentation Rate–H₂S Concentration Model highlights how rapid sedimentation and abundant availability of ³⁴S-enriched H₂S promote extraordinarily TOC enrichment in inner-shelf settings, while slower burial and limited H₂S availability inhibit TOC accumulation in outer-shelf locations. The Kwangsian Orogeny–Hydrographic Restriction Model associates tectonic uplift with enhanced hydrographic restriction, reducing sulfate supply and driving the diachronous termination of high TOC intervals across the platform. These insights refine our understanding of early Silurian black-shale deposition and offer practical guidance for future shale-gas exploration in South China.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107588"},"PeriodicalIF":3.6,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144988702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical insights into authigenic pyrite formation in central Yellow Sea sediments: influence of sedimentary environment and microbial sulfate reduction","authors":"Yu Gu ,&nbsp;Xin Chang ,&nbsp;Xiting Liu ,&nbsp;Mingyu Zhang ,&nbsp;Yanfei An ,&nbsp;Guangchao Zhuang ,&nbsp;Houjie Wang","doi":"10.1016/j.marpetgeo.2025.107587","DOIUrl":"10.1016/j.marpetgeo.2025.107587","url":null,"abstract":"<div><div>Authigenic pyrite is a key archive of paleo-redox conditions and sulfur cycling in marine sediments, yet its formation mechanisms under variable marginal sea environments remain incompletely understood. This study investigates the formation of authigenic pyrite in Holocene sediments from the central Yellow Sea, focusing on its morphology, sulfur isotopes, and environmental controls. Pyrite formation is primarily constrained by the availability of reactive organic carbon, as revealed by total organic carbon–total sulfur relationships (C/S ratios) and reactive iron content. High C/S ratios suggest that the supply of organic matter, rather than the availability of sulfate or iron, plays the dominant role. Framboidal pyrite is the most common morphology. These framboids consist of tightly packed microcrystals, primarily octahedral and truncated octahedral in shape, indicating rapid precipitation under early diagenetic, low-oxygen, and low-energy conditions. The sulfur isotopes of pyrite (δ³⁴S_pyr, Vienna Canyon Diablo Troilite; V-CDT) range from −47.4 ‰ to −7.8 ‰, reflecting large fractionations associated with microbial sulfate reduction (MSR). The vertical δ³⁴S_pyr profile shows transitions from open- to closed-system MSR regimes, modulated by changes in sedimentation rate, freshwater input, and stratification linked to the Yellow Sea Cold Water Mass. These findings reveal the interplay between sedimentary environment, pyrite morphology, and sulfur isotope composition, offering insights into sulfur cycling in modern marginal marine settings and ancient analogues.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107587"},"PeriodicalIF":3.6,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144931635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}