Marine and Petroleum Geology最新文献

{"title":"Thermal records of carbonate cements: Deciphering the hydrothermal imprint on Eocene Shahejie Formation sandstones in the northern Dongying Depression, China","authors":"Yishan Gao ,&nbsp;Shifa Zhu ,&nbsp;Hang Cui ,&nbsp;Wendian Cai ,&nbsp;Ruihang Zhang","doi":"10.1016/j.marpetgeo.2025.107513","DOIUrl":"10.1016/j.marpetgeo.2025.107513","url":null,"abstract":"<div><div>The carbonate cements in the sandstones of the Eocene Shahejie Formation in the Dongying Depression record crucial temporal and thermal information related to hydrothermal activity. This study presents a comprehensive investigation of these carbonate cements, detailing their diagenetic process, chronological formation, and material origins. Sedimentological evidence indicates that the sandstones in the study area were predominantly deposited in deltaic and marginal lacustrine settings, with a subdivision into matrix-rich and matrix-poor types at the microscale. Petrographic observation and electron probe microanalysis (EPMA) reveal that calcite is the predominant authigenic mineral phase, exhibiting variability in both abundance and morphology depending on sandstones maturity. Matrix-poor sandstones, characterized by higher maturity, predominantly exhibit blocky calcite cement, whereas those with a rich matrix and lower maturity tend to develop scattered patchy calcite. Fluid inclusion homogenization temperatures indicate that these calcite cements precipitated under abnormally high-temperature conditions, ranging from 85 to 350 °C. And the carbonate cements exhibit low δ¹³C (−11.8 to −3.1 ‰ VPDB) and δ¹⁸O (clustered tightly from −14.0 to −11.1 ‰ VPDB) values, interpreted to reflect a mixed source comprising magmatic CO₂, air CO₂, and a potential contribution from soil CO₂. <em>In situ</em> U-Pb isotopic dating of calcite constrains the timing of carbonate cement precipitation, with ages ranging from 39.4 ± 1.9 Ma to 42 ± 7.6 Ma. Ultimately, the results indicate that the calcium source for the carbonate cements in the Eocene Shahejie Formation sandstones of this region is primarily a mixture of primary alkaline formation waters and hydrothermal fluids. The carbon source is dominated by a mixture of magmatic CO₂ and air CO₂, with a potential minor contribution from soil CO₂. This study suggests that the hydrothermal activity influencing carbonate cementation in the study area was likely associated with the Cenozoic subduction of the New Pacific Plate. Through the integration of multiple advanced analytical techniques, this study elucidates the material origins and precipitation timing of hydrothermal derived carbonate cements, validating the potential application of advanced techniques such as <em>in situ</em> U-Pb isotopic dating of calcite in clastic rock research. Additionally, the hydrothermal activity age determined for the Shahejie Formation in this study provides crucial data support for the research on tectonic-magmatic activity in the Dongying Depression.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107513"},"PeriodicalIF":3.7,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144298830","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":"Multistage fluid activity as a control on the Ediacaran carbonate reservoirs in the Sichuan Basin, SW China","authors":"Tao Luo ,&nbsp;Xiaowen Guo ,&nbsp;Tiago M. Alves ,&nbsp;Zhiliang He ,&nbsp;Ze Tao ,&nbsp;Yahao Huang","doi":"10.1016/j.marpetgeo.2025.107509","DOIUrl":"10.1016/j.marpetgeo.2025.107509","url":null,"abstract":"<div><div>The Ediacaran Dengying Formation (Z₂dn) of the Sichuan Basin, Southwestern China, experienced multi-stage fluid flow, which accompanied the reduction and modification of reservoir porosity. Porosity in the Z₂dn carbonate reservoir thus varies in different structural units. Fluid inclusion and implications for reservoir porosity were investigated by combining petrographic, geochemical, fluid inclusion, in-situ U-Pb geochronological, and basin modelling data. Three stages of dolomite cements (CD-1, CD-2, and CD-3) and one stage of dolomite veining (FD) were petrographically, geochemically, and geochronologically distinguished in reservoir rocks, and respectively dated at c. 453 Ma, 336 Ma, and 173 Ma. Two stages of dolomite and quartz cement formation (CD-1, CD-2, Qtz-1, and Qtz-2) were subsequently formed at c. 453 Ma, 298 Ma, 182 Ma, and 165 Ma. CD-1, CD-2 cements and FD veins were interpreted as diagenetic fluids and formed in the sealed environment during the Late Ordovician-Early Permian; they led to multi-stage cementation of reservoir intervals and a reduction in porosity. Importantly, the diagenetic sequences between bitumen and dolomite generation phases indirectly define the dates of two oil charging events. The first episode only occurred in the central Sichuan Basin during the Silurian, and its timing is constrained by the absolute ages of CD-1 and CD-2 cements. The second oil charging episode was the most important in the Sichuan Basin and occurred during Indosinian tectonics according to the trapping temperatures of bitumen-bearing inclusions in Qtz-1 veins. Also significantly, oil charge was able to inhibit the precipitation of authigenic minerals in reservoir intervals. Oil cracking in the Z₂dn reservoir occurred at 173-165 Ma, accompanied by weak overpressure generation in the southeastern Sichuan Basin and medium-intensity overpressure in the central Sichuan Basin. Once again, it prevented compaction and solution compaction to maintain reservoir porosity. Moreover, CD-3 and Qtz-2 cements were possibly derived from hydrothermal fluid, which led to the dissolution of the Z₂dn dolomite reservoir. As corollary, the numerous stages of dolomite cementation recorded here, the recognition of a single episode of oil charge, and weak reservoir overpressures, are the main factor contributing to a lower porosity development in the southeastern Sichuan Basin when compared to the central Sichuan Basin. These results have profound implications to the economic potential of similar oil and gas prospects deep in lower Paleozoic rocks across the world.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107509"},"PeriodicalIF":3.7,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144288966","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":"A sequence boundary related aeolian sand record in a continental basin: The Cretaceous-Paleogene White Sandstone Member, Tabei Uplift, Tarim Basin, NW China","authors":"Xiaoyang Gao ,&nbsp;Luxing Dou ,&nbsp;Wenxiang He ,&nbsp;Qi Sun ,&nbsp;Zhenli Yi ,&nbsp;Bin Li ,&nbsp;Qiaolin He ,&nbsp;Jineng Jin ,&nbsp;Yong Hu ,&nbsp;Jingwen Yan ,&nbsp;Li Zhang","doi":"10.1016/j.marpetgeo.2025.107514","DOIUrl":"10.1016/j.marpetgeo.2025.107514","url":null,"abstract":"<div><div>A sequence boundary typically corresponds to an unconformity, with fluvial incised-valley fills representing a classic depositional model. However, aeolian deposits associated with sequence boundaries, though equally significant, have received less attention in studies of continental basins. Therefore, this study investigates aeolian sand sedimentary records near a sequence boundary in a continental basin based on an integrated analysis of 3D seismic volumes, wireline logs and cores from the Cretaceous-Paleogene deposits in the Tabei Uplift (Tarim Basin, NW China). The Cretaceous-Paleogene White Sandstone Member was formed in a salt-lake margin desert environment above a local unconformity surface that is well recognized on seismic profiles. The studied sandstone sequence is characterized by its friable texture and exhibits distinctive aeolian depositional features, including developed grainfall strata and grainflow strata within the core samples. Scanning electron microscopy (SEM) analysis reveals the presence of abundant dish-shaped impact pits on quartz grain surfaces, providing compelling evidence for the aeolian origin of these sandstones. During the Late Cretaceous to Paleogene period, the study area underwent significant geomorphological changes due to the tectonic uplift of the Tianshan and Kunlun Orogenic Belts. This tectonic activity resulted in the progressive erosion of Cretaceous strata in both the northwestern and southeastern regions of the research area. During this period, with regression of the Tarim Sea, aridity gradually increased, leading to the formation of extensive aeolian sands in the area. The aeolian sandstone pinches out from the southeast to the northwest in the area east of the WM7 fault belt. In the Paleogene, incised valleys were developed and transported eroded aeolian sands to the salt lake in the northwest. This study demonstrates the transformation of Cretaceous-Paleogene aeolian sand in a \"sandstone factory\" in the northern Tarim Basin during a greenhouse period. The \"sandstone factory\" provides an opportunity for research on sequence boundary-related aeolian sandstone unrelated to a fluvial incised valley in a continental basin.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107514"},"PeriodicalIF":3.7,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331072","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":"Cutting-edge reverse time migration imaging of the hydrocarbon deposits in the Outer Carpathian fold-thrust belt","authors":"Tomasz Maćkowski ,&nbsp;Aurelia Zając ,&nbsp;Piotr Hadro ,&nbsp;Adam Cygal ,&nbsp;Michał Stefaniuk","doi":"10.1016/j.marpetgeo.2025.107515","DOIUrl":"10.1016/j.marpetgeo.2025.107515","url":null,"abstract":"<div><div>The Western Outer Carpathian fold-thrust belt is an example of strongly tectonically disturbed rock formations characterized by steeply dipping, narrow folds. The results of seismic surveys conducted in that region were used to evaluate the efficiency of the Pre-Stack Depth Migration using Reverse Time Migration (PreSDM RTM) processing workflow to enhance and detail the seismic imaging of geological structures. The analysis focused on seismic imaging of three hydrocarbon accumulations discovered using surface geological mapping methods long before the seismic methods were implemented into the hydrocarbon exploration.</div><div>The key problem in the application of the RTM algorithm is the construction of a highly accurate seismic velocity field. In this study, two inversion methods were used for this purpose: gravity inversion and the Early Arrival Waveform Inversion, employing as initial velocity model one derived from well-log data and standard refraction tomography. The effectiveness of the PreSDM RTM was assessed using both isotropic and anisotropic algorithms, particularly employing the TTI anisotropy variant due to the geological structure.</div><div>The results obtained showed that RTM migration enables the imaging of challenging details of strongly tectonically disturbed structures in the Carpathian fold-thrust belt, such as steep and tight folds or small-displacement faults. The best seismic imaging was achieved using TTI RTM algorithm, whose additional advantage is the accurate horizontal positioning of fold culminations being potential hydrocarbon traps, which is crucial for the proper location of drilling sites. The RTM efficacy was confirmed by good imaging of shallow hydrocarbon accumulations, whose geological structure is recognized by drillings.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107515"},"PeriodicalIF":3.7,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331073","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":"Dynamic model for charging tight gas reservoirs: A case study from the Xujiahe Formation in the Sichuan Basin, China","authors":"Haoming Shao ,&nbsp;Min Wang ,&nbsp;Junfeng Cui ,&nbsp;Hui Jin ,&nbsp;Dianshi Xiao ,&nbsp;Yidong Jia ,&nbsp;Wei Li ,&nbsp;Xiaodie Guan ,&nbsp;Chen Zhao ,&nbsp;Tao Zhang","doi":"10.1016/j.marpetgeo.2025.107512","DOIUrl":"10.1016/j.marpetgeo.2025.107512","url":null,"abstract":"<div><div>As an important unconventional natural gas resource, the occurrence of tight gas is of great significance for the accumulation of natural gas. However, the charging process of tight gas is complex and diverse. Although previous studies have mainly focused on individual charging parameters, there is a lack of research on the coupling of multiple factors on the control of the charging process of tight gas. Consequently, this paper uses an example from the tight sandstones of the Upper Triassic Xujiahe Formation, Sichuan Basin, China, to elucidate insights by employing physical charging simulation of nuclear magnetic resonance (NMR) coupling displacement combined with physical property analyses, scanning electron microscopy (SEM), X-ray diffraction (XRD), and high-pressure mercury injection (HPMI) experiments. The principal findings are: (1) The tight reservoirs of the Xujiahe Formation can be classified into four types based on the differences in pore structure. From Type I to IV reservoirs, chlorite coatings and dissolution progressively weaken, with pore characteristics (as shown by NMR T₂ spectra) transitioning from a bimodal distribution dominated by macropores to a unimodal distribution characterized by micropores. (2) The charging process of tight gas is divided into three stages: low-pressure rapid charging stage (A), medium-high pressure slow charging stage (B), and late non-continuous slow charging stage (C). Type I reservoirs are mainly charged in stage A, Types II and III reservoirs in stage B, and Type IV reservoirs in stage C. (3) The charging process of tight gas is controlled by a combination of charging pressure, pore structure, and water film. Higher charging pressure has a significant impact on the gas content of poor reservoirs. Under the same charging pressure, the gas saturation decreases with the decrease in of pore size. As the charging pressure increases, the influence of the water film diminishes. (4) Through multi-factor analysis, a tight gas saturation evaluation model is established that considers reservoir types and pressure and can predict the tight gas charging process and gas saturation in different types of tight reservoirs. This research not only aids in understanding the accumulation process of tight gas but also provides a theoretical foundation for the accurate prediction of tight gas sweet spots.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107512"},"PeriodicalIF":3.7,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144307066","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":"Main controls on nitrogen cycling and Mo-U enrichment of the Middle Triassic Chang 7 Member in the Ordos Basin: Implications for redox and ultra-organic enrichment in a giant highly productive lake","authors":"Chuhan Zhao ,&nbsp;Xiaodong Liu ,&nbsp;Wanglu Jia ,&nbsp;Wenzheng Zhang ,&nbsp;Jian Chen ,&nbsp;Jinbu Li ,&nbsp;Ping'an Peng","doi":"10.1016/j.marpetgeo.2025.107508","DOIUrl":"10.1016/j.marpetgeo.2025.107508","url":null,"abstract":"<div><div>During the deposition of the Chang 7 Member (∼241.5 Ma) black shale from the Yanchang Formation in the Ordos Basin, a giant and deep perennial lake developed. This deposition represents a substantial organic carbon burial, and this lake serves as a significant focus for investigating the ecosystem recovery and environmental evolution following the end-Permian mass extinction (EPME). Due to potential influences from volcanic-hydrothermal activity and terrigenous detrital input, the primary controls on nitrogen (N) and redox-sensitive trace element enrichment remain unclear, leading to ongoing debates regarding the lake's redox conditions inferred from these proxies. This study examines the main controls on the different isotopic compositions of N species and the enrichment of redox-sensitive trace elements (RSTEs) in deep lake facies drill cores. The following conclusions can be drawn: (1) The high total N content (averaging 1.11 %) and inorganic N content (accounting for 65 % of total N) are likely influenced by terrigenous detrital input. This input also affects N isotope composition, leading to summarized results of bulk δ¹⁵N_bulk values being lower than δ¹⁵N_ker (δ¹⁵N of the kerogen) values (average 2.4 ‰). Other post-depositional factors, including thermal maturation and retained oil, do not significantly affect the organic N isotopes, thereby enhancing their reliability for N cycling analysis. (2) The notable enrichments of Mo and U in the Chang-7 source rocks, with Mo_EF values reaching 90.8 and U_EF values of 13.9, were primarily controlled by strong adsorption of metal sulfides and organic matter under anoxic-euxinic bottom water conditions, with additional input from hydrothermal activities. (3) Under anoxic-euxinic bottom water conditions, moderate δ¹⁵N_ker values (∼4.5 ‰) and decreasing δ¹⁵N_ker in deeper facies indicate a deep redox chemocline with an metalimnetic oxygen minimum near the lake's margin. N cycling was primarily dominated by denitrification but with a notable contribution from nitrogen fixation, while nitrates and ammonium were the primary bio-limiting nutrients in the metalimnetic oxygen minimum. Factors such as global cooling, which facilitated ecological recovery after the EPME, and local volcanic-hydrothermal activities that enhanced weathering and nutrient input, may have promoted primary production and development of anoxic bottom water in this large lake, ultimately fostering the anomalous accumulation of organic material.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107508"},"PeriodicalIF":3.7,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144272153","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":"Integrated sedimentological and geochemical characterization of the Silurian Qalibah Formation in central Saudi Arabia: Implications to paleoenvironmental reconstruction and organic richness evaluation","authors":"Mutasim Osman ,&nbsp;Korhan Ayranci ,&nbsp;Khairul Azlan Mustapha ,&nbsp;Eduardo Gramajo ,&nbsp;Rached Maurice Rached ,&nbsp;Thomas Finkbeiner ,&nbsp;Mahmoud Mowafi","doi":"10.1016/j.marpetgeo.2025.107498","DOIUrl":"10.1016/j.marpetgeo.2025.107498","url":null,"abstract":"<div><div>Unconventional hydrocarbon reservoirs are challenging due to their vertical and lateral heterogeneities. The Silurian Qalibah Formation in Saudi Arabia comprising of the Qusaiba and Sharawra members, serves as a prime example. This study investigates reservoir heterogeneity and variations in depositional conditions to produce a high-resolution chemozonation of the Qalibah Formation. Mineralogical and elemental compositions were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD), while organic matter characterization was performed using Rock-Eval pyrolysis. Three facies were identified: laminated grey-red mudstones in the Qusaiba Member, heterolithic sandstone-mudstone alternation in the lower Sharawra Member, and thickening upward fine sandstones in the upper Sharawra Member. Clay minerals dominate the Qusaiba Member (50 %), while quartz, mica, and K-feldspars prevail in the Sharawra Member. Organic matter is in early maturation stage with poor-to-fair total organic carbon (TOC) content, averaging 0.2 wt% in the Qusaiba Member and 0.05 wt% in the Sharawra Member. Detrital influx proxies indicate higher sedimentation rates in the Sharawra Member compared to the Qusaiba Member. Paleoclimatic proxies suggest humid to semi-arid conditions in the Qusaiba Member and semi-arid to arid conditions in the Sharawra Member. Paleomarine proxies consistently reveal brackish to saline and suboxic to oxic conditions. Five chemozones were established: three in the Qusaiba Member (Q-1: Ti/P depletion; Q-2: elevated TOC; Q-3: spiking Sr/Ba) and two in the Sharawra Member (S-1: lower Zr/Al and Sr/Cu than S-2). This chemozonation highlights spatial-temporal geochemical variability, offering insights into depositional dynamics and reservoir heterogeneity. The framework supports chemo-steering applications to optimize drilling, enhance reservoir targeting, and improve hydrocarbon recovery in analogous unconventional systems.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107498"},"PeriodicalIF":3.7,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144272235","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":"Bimodal volcanism during the Early Cretaceous in Santos Basin, Brazil: Mantle-crust interaction, thermal regimes, CO2 influx and coeval magma generation onshore and offshore the South Atlantic volcanic rifted margins","authors":"Bárbara Santos Queiroz ,&nbsp;Sergio de Castro Valente ,&nbsp;Anderson Costa dos Santos ,&nbsp;Monica Heilbron","doi":"10.1016/j.marpetgeo.2025.107495","DOIUrl":"10.1016/j.marpetgeo.2025.107495","url":null,"abstract":"<div><div>There are many sedimentary basins along the South Atlantic rifted margins with voluminous hydrocarbon reservoirs. It evolves from rift to drift tectonic stages give rise to geological processes that control part of their petroleum systems. Some of these processes are related to changes in thermal regimes due to long-standing tectono-magmatic events associated to mantle-crust interactions. The Santos Basin, offshore southeast Brazil, contains the country's largest oil and gas reservoirs. Its origin is related to the rift process that led to the Gondwana breakup during the Early Cretaceous. This paper presents wellbore, petrographic, geochemical, isotopic and geochronological data obtained for an 800m-tick magmatic section recorded along the so-called pre-salt sedimentary sequence in the well 6-BG-6P-SPS in the Santos Basin. This magmatic section comprises effusive mafic and composite felsic rocks associated with long-standing bimodal volcanism (135-122 Ma). The geochemical models allowed to propose that the basic mafic and acid felsic rocks are no-cogenetic by differentiation processes, although some of the basic and intermediate liquids can be linked by AFC within the upper continental crust. The enriched isotope signature of the basic rocks can be explained by geodynamic processes involving the Tristan da Cunha plume and enriched portions of the SCLM (EMII-like mantle reservoir). The data were used to propose conceptual models for the mantle geodynamics and the tectono-magmatic settings from the Hauterivian to Aptian. These models show how mantle-crust tectonic and magmatic interactions imposed thermal regimes that may have controlled geological processes, hydrothermalism and CO₂ influx recorded in the pre-salt petroleum systems in the Santos Basin.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107495"},"PeriodicalIF":3.7,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290493","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":"The evolution of organic matter sources and sedimentary environments in lakes during the Eocene Climatic Optimum","authors":"Chuan Xu ,&nbsp;Guangrong Peng ,&nbsp;Pei Liu ,&nbsp;Ye He ,&nbsp;Peimeng Jia ,&nbsp;Xuanlong Shan ,&nbsp;Guoli Hao ,&nbsp;Mengrong Shen ,&nbsp;Kang Li","doi":"10.1016/j.marpetgeo.2025.107496","DOIUrl":"10.1016/j.marpetgeo.2025.107496","url":null,"abstract":"<div><div>The global climate experienced many rapid and long-term warming events during the early–middle Eocene, and these warming events had a significant impact on the evolution of the global paleoecosystem and led to the widespread development of organic-rich fine-grained sediments worldwide during the same period. To elucidate the regulatory effects of early–middle Eocene warming events on the organic matter (OM) sources and sedimentary environments of paleolakes, in this study, which is based on a detailed analysis of organic petrology, mineralogy, bulk geochemistry and biomarkers of typical wells, combined with a previous understanding of paleoclimate and hydrothermal activities, the influences of warming events on the OM sources and sedimentary environments of early–middle Eocene lakes were systematically investigated. The results demonstrate that units I and III, which were deposited under warm and humid climates, experienced massive freshwater influxes, highstand lacustrine conditions, and dysoxic–anoxic bottom waters, fostering the codominance of algae and terrestrial vascular plants. In contrast, units II and IV record lacustrine salinization events under warm semiarid–semihumid climates and synsedimentary hydrothermal activity, marked by increased salt-tolerant/thiophilic bacteria and euxinic bottom conditions linked to salinity stratification and hydrothermal sulfur cycling. The climatic transition from warm–humid to hyperthermic and semihumid–semiarid conditions during deposition of the Wenchang Formation triggered the amplification of lacustrine biodiversity and expansion of the oxygen minimum zone. Salinization-driven ecosystem restructuring, coupled with elevated primary productivity and exceptional preservation, resulted in organic-rich mudstones with high hydrocarbon generation potential. This study fully reveals the effects of paleoclimate fluctuations during warm periods on the evolution of the ecological environment of paleolakes, thus providing key geological information for deciphering the OM enrichment mechanism in early–middle Eocene paleolakes.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107496"},"PeriodicalIF":3.7,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144231618","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":"Impact of burrows on electrical resistivity: Example from the Jurassic Hanifa Formation, Saudi Arabia","authors":"Ahmed Nagy ,&nbsp;Hassan A. Eltom ,&nbsp;Ammar El-Husseiny ,&nbsp;John D. Humphrey ,&nbsp;Mohammed Al Hamad","doi":"10.1016/j.marpetgeo.2025.107497","DOIUrl":"10.1016/j.marpetgeo.2025.107497","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Although the influence of burrows on porosity and permeability is well documented, their impact on electrical properties remains poorly understood. The study addresses this gap by employing an integrated methodology, focusing primarily on high-resolution imaging to facilitate digital rock analysis, and customized resistivity setups developed for analyzing 4-inch diameter core samples from the Hanifa Formation in central Saudi Arabia. The setups allow for detailed analysis of the cores on a 4-inch diameter scale, alongside field observations, petrography, and petrophysical measurements. The primary objective is to test the hypothesis that the resistivity of sedimentary strata characterized by passively filled burrows varies inversely with the percentage and connectivity of burrows, particularly where the burrows are connected along the core from bottom to top. CT scans provided detailed insights into burrow connectivity and pore structures within the burrow fillings, enabling quantification of burrow percentages. Surprisingly, the burrow percentage exhibited a strong positive correlation with bulk resistivity measurements (p-value &lt;0.05, r&lt;sup&gt;2&lt;/sup&gt; = 0.98), contradicting the initial expectation that increasing burrow percentages, resulting in connected burrow networks saturated with brine, would lead to reduced resistivity. Further investigation with high-resolution radial resistivity measurements at a centimeter scale revealed a similar positive correlation between resistivity and burrow percentage (p-value &lt;0.05, r&lt;sup&gt;2&lt;/sup&gt; = 0.86). To explain these unexpected results, petrographic analysis and CT imaging were used to examine the rock texture of the studied cores. Micro CT scans revealed that what appeared to be connected interparticle and moldic pores in the petrographic data were, in fact, isolated in three dimensions, preventing the formation of permeability pathways within the burrow fillings. As a result, the burrow networks did not hold connected fluid phase or contribute to electrical current transmission, likely explaining the positive correlation between burrow percentage and resistivity. Further core flooding results confirm what has been observed in CT scan data by yielding very low permeability (∼3 mD) in cores with a connected burrow network. Additionally, porosity measurements indicated that the surrounding burrow matrix is highly porous, with microporosity accounting for more than 70 % of total porosity. The microporosity acted as the primary conductor of electrical current, creating a short-circuiting effect that dominated the resistivity readings. The study suggests that for burrows to affect resistivity inversely, they must be both connected and permeable. When burrows do not form permeability pathways in a microporous matrix, resistivity may vary proportionally with their presence. These findings provide valuable insights into the relationship between burrows and electrical resistivity in sedimentary stra","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"181 ","pages":"Article 107497"},"PeriodicalIF":3.7,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144279756","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}