Marine and Petroleum Geology最新文献

{"title":"The methane-sulfate transition interface in offshore sediments serves as a critical boundary for abrupt transitions in sedimentary environments","authors":"Xue Li ,&nbsp;Xiaoyong Duan ,&nbsp;Ping Yin ,&nbsp;Ke Cao ,&nbsp;Xingliang He ,&nbsp;Jianghai Yang ,&nbsp;Bin Chen","doi":"10.1016/j.marpetgeo.2025.107362","DOIUrl":"10.1016/j.marpetgeo.2025.107362","url":null,"abstract":"<div><div>Methane is commonly observed in unconsolidated sediments prevalent coastal areas. It widely acknowledged within the scientific community that the methane-sulfate transition zone (SMTZ) forms due to the upward diffusion of methane and downward diffusion of sulfate within these sedimentary environments. However, this study presents a detailed analysis using a borehole sample from the continental shelf of the East China Sea as a representative case study, revealing distinct findings. The entire borehole was 60 m long and predominantly composed of clay with extremely fine sediment particles, conditions that are inherently unfavorable for diffusion. The SMTZ was identified at a depth of 9 m. Geochemical characteristics of the sediments showed significant differences above and below this interval. The carbon-to-nitrogen (C/N) ratios, the carbon isotopic compositions of total organic carbon (TOC), and nitrogen isotopic compositions of total nitrogen (TN), etc., all showed a peak at this specific depth. Additionally, elements such as thorium (Th), vanadium (V), cobalt (Co), and nickel (Ni), along with redox condition indicators such as the Ni/Co and Th/U ratios, demonstrated abrupt changes around the 8.5 m mark. The findings of this study suggest that the SMTZ functions as a transitional interface within the sedimentary environment, rather than merely representing the boundary where methane and sulfate converge. This insight is crucial for enhancing our comprehension of global carbon cycling in marine sediments, as prevailing estimates of methane release fluxes based on concentration gradient diffusion theory may lead to significant discrepancies between estimated and actual values.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"176 ","pages":"Article 107362"},"PeriodicalIF":3.7,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Do hydrothermal fluids cause a dilution effect on organic matter in the Early Cambrian marine black shales?","authors":"Hezheng Dong ,&nbsp;Dongsheng Zhou ,&nbsp;Xiaowei Huang ,&nbsp;Yufei Liang ,&nbsp;Lei Huang ,&nbsp;Jie Xu","doi":"10.1016/j.marpetgeo.2025.107361","DOIUrl":"10.1016/j.marpetgeo.2025.107361","url":null,"abstract":"<div><div>Hydrothermal fluids play a significant role in the formation of black shales. However, most previous studies have focused on their positive impacts on the formation and enrichment of organic matter (OM), while overlooking potential dilution effects. This study uses organic geochemistry, elemental geochemistry, and field emission scanning electron microscopy (FE-SEM) to examine the marine black shales of the Lower Cambrian Hetang Formation at the Hongtao (HT) section in southern Anhui Province and the contemporaneous Niutitang Formation at the Yangtiao (YT) section in Guizhou Province, China. We systematically analyze the paleo-environmental conditions and the influence of hydrothermal activity during the formation of black shales with varying OM abundances. Our findings show that black shales with different OM abundances in the HT and YT section exhibit similar paleo-productivity, paleo-redox conditions, and sedimentation rates, and all show evidence of hydrothermal sedimentation. Notably, hydrothermal activity significantly affects the content of non-terrestrial silicon (Si_ex), which strongly correlates negatively with total organic carbon (TOC). This suggests that an increased silicon flux due to hydrothermal processes leads to OM dilution. Additionally, we explore the origin of silicon, suggesting that hydrothermal sources are a critical contributor to silicon in shales. We develop a silicon cycling model for black shale formation, which highlights the dual role of hydrothermal activity: promoting OM formation and enrichment yet also causing dilution. This study emphasizes the importance of considering both nutrient transport, enhanced anoxia, and OM dilution when evaluating the influence of hydrothermal activity on black shale formation. Our findings offer new insights into the complex interactions between hydrothermal processes and OM dynamics, providing significant scientific implications for a deeper understanding of black shale formation.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"176 ","pages":"Article 107361"},"PeriodicalIF":3.7,"publicationDate":"2025-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534593","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":"Diagenetic fluid evolution and its implication for hydrocarbon accumulation in Ordovician carbonate of the Tazhong area, Tarim Basin: Constraints from petrology, fluid inclusions, and geochemistry of calcite cements","authors":"Haocheng Liu ,&nbsp;Chengyan Lin ,&nbsp;Chunmei Dong ,&nbsp;Guoqiang Luan ,&nbsp;Lihua Ren ,&nbsp;Guoyin Zhang ,&nbsp;Yintao Zhang ,&nbsp;Baozhu Guan","doi":"10.1016/j.marpetgeo.2025.107360","DOIUrl":"10.1016/j.marpetgeo.2025.107360","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Ordovician carbonate reservoirs in the Tarim Basin have undergone multiple tectonic events and fluid activities, complicating reservoir quality. Understanding these fluid-rock interaction processes is critical for unraveling reservoir heterogeneity evolution and hydrocarbon migration chronostratigraphy. Multiple generations of carbonate cements in fault-related reservoirs preserve important fluid activity signatures, providing constraints on fault reactivation, vertical hydrocarbon migration pathways, and accumulation preservation mechanisms. This investigation systematically examines fault-zone hosted carbonate cements and fracture-filling vein assemblages obtained from well cores, with particular emphasis on their fluid origins and the evolutionary processes. We utilized an integrated approach incorporating petrographic analysis, fluid inclusion microthermometry, and geochemical techniques to identify two distinct generations of fault-associated carbonate cements and three discrete phases of calcite veins, listed chronologically from oldest to youngest: fibrous calcite cements (C1), blocky calcite cements (C2), fracture-filling fine calcite cements (C3), coarser blocky calcite vein cements with zoned cathodoluminescence (C4), and last fracture-filling coarse calcite cements (C5).&lt;/div&gt;&lt;div&gt;The carbon and oxygen isotopic composition of C1, similar to well-preserved Ordovician carbonate rocks, along with its fibrous texture and near-micritic grain size, suggests formation during the early diagenetic stage under a marine environment. The lighter δ&lt;sup&gt;18&lt;/sup&gt;O (av. = −7.12‰ ± 0.40‰ VPDB) and lower Sr (av. = 183.75 ± 32.30 ppm) content of C2 indicate precipitation during shallow burial diagenesis. Early vein cement (C3) containing single-phase liquid inclusions suggests precipitation in a near-surface environment. The estimated δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;fluid&lt;/sub&gt; and REE&lt;sub&gt;SN&lt;/sub&gt; patterns, which parallel the seawater profile, further support the parent fluid of C3 originated from primary marine water. The slightly depleted δ&lt;sup&gt;13&lt;/sup&gt;C values (av. = −0.97‰ ± 1.02‰) of C4 reflect external organic carbon input. Additionally, the δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;fluid&lt;/sub&gt; and river-like REE&lt;sub&gt;SN&lt;/sub&gt; patterns, reflecting parent fluid of C4 was derived from a mixture of meteoric and marine water. The non-CL vein cement of C5 displays more depleted δ&lt;sup&gt;18&lt;/sup&gt;O (av. = −10.98‰ ± 1.24‰) value and higher Fe (av. = 34 513.66 ± 269.3 ppm) and Mn (av. = 248.86 ± 104.85 ppm) concentrations, indicating its precipitation in an intermediate to deep burial reducing environment. The higher δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;fluid&lt;/sub&gt; values, combined with higher temperatures and salinities, are consistent with a burial basin brine origin.&lt;/div&gt;&lt;div&gt;Consequently, we developed a spatial-temporal evolution model of fault-related fluid circulation. The driving mechanism of marine-meteoric mixed fluid circulation is associated with extensive exposure and erosion events ","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"176 ","pages":"Article 107360"},"PeriodicalIF":3.7,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551908","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":"Inconsistencies in stratigraphic interpretation and correlation – Comments on “depositional cyclicity of lower Cambrian strata in the NW Himalayas: Regional sequence stratigraphy of the Indian passive margin” by Mahmood et al. (2024)","authors":"Malik Muhammad Saud Sajid Khan ,&nbsp;Bing Pan ,&nbsp;Maoyan Zhu","doi":"10.1016/j.marpetgeo.2025.107351","DOIUrl":"10.1016/j.marpetgeo.2025.107351","url":null,"abstract":"<div><div>This article comments on a recent study by Mahmood et al. (2024) on the lower Cambrian strata across the NW Himalaya. While providing a detail sequence stratigraphic framework, the authors fail to adequately considered recent developments in the Cambrian chronostratigraphic framework of the Himalaya and misinterpreted the age of rock successions, which currently range from late Cryogenian to middle Cambrian, as “Lower Cambrian” (ca. 538-512 Ma). This stratigraphic discrepancy introduced considerable confusion, disrupting the recently revised and established late Neoproterozoic to early Cambrian stratigraphic framework across the Himalaya. Consequently, this necessitates a reevaluation of their inferred depositional history and sequence stratigraphic interpretation, as these misinterpretations directly impact the timing, duration, and correlation of depositional events and sea-level changes they described. Present comments seek to address key stratigraphic uncertainties identified in the study by Mahmood et al. and offer clarity to the conflicting interpretations based on more appropriate references related to the chronostratigraphic aspects of the commented paper. This effort not only contextualized rock units being discussed within their established stratigraphic context but also facilitated future research on more precise correlation and subdivision of the late Neoproterozoic-early Cambrian strata at both regional and global scales.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"177 ","pages":"Article 107351"},"PeriodicalIF":3.7,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143580764","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":"Application of nuclear magnetic resonance technology in reservoir characterization and CO2 enhanced recovery for shale oil: A review","authors":"Lu Wang ,&nbsp;Yi Du ,&nbsp;Gang Wu ,&nbsp;Xiaofei Fu ,&nbsp;Chenlu Xu ,&nbsp;Zhejun Pan","doi":"10.1016/j.marpetgeo.2025.107353","DOIUrl":"10.1016/j.marpetgeo.2025.107353","url":null,"abstract":"<div><div>The reservoir characterization and development for shale oil faces significant challenges due to low porosity, low permeability, multi-scale pore space, and complex fluid composition. Nuclear magnetic resonance (NMR)technologies applied in shale oil reservoirs include one-dimensional (1D) NMR T₂ map, two-dimensional (2D) NMR T₁-T₂ map, nuclear magnetic imaging (MRI) technology, and stratified T₂ technology. The 1D T₂ map nondestructively characterizes the full-scale pore size distribution (PSD) of shale oil reservoirs and can be combined with other experimental methods to extend the functions: (1) Through combining with centrifugation and thermal treatment, the NMR T₂ cutoff value can be determined to quantitatively distinguish movable fluid, capillary bound fluid, and immovable fluid; (2) In conjunction with a confining core holder, stress sensitivity of the shale matrix and fracture systems can be characterized; (3) Through combining with spontaneous imbibition experiments, the spontaneous imbibition characteristics and wettability can be quantitatively evaluated; (4) Based on an online high-temperature and high-pressure CO₂ enhanced shale oil recovery (CO₂-ESOR) apparatus, dynamic oil recovery factors can be quantitatively calculated. Furthermore, the 2D T₁-T₂ map has unique advantages in the identification of various fluid types and in-situ content of fluids in different occurrence states in shale oil reservoirs. MRI technology has significant potential to characterize the spatial distribution of the gas-liquid interface during the CO₂-ESOR process. However, current resolution capabilities are generally inadequate for imaging shale oil reservoir samples, particularly those with low porosity and permeability. The stratified T₂ technology provides spatially resolved T₂ distributions and profiles of oil saturation in shale oil reservoirs. However, these applications still face challenges, such as developing novel probes, mitigating the impact of paramagnetic minerals on NMR measurement, and enhancing the resolution capabilities of MRI technology. The continuous advancement of NMR technology will further enhance the applications in the exploration and development of shale oil reservoirs.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"177 ","pages":"Article 107353"},"PeriodicalIF":3.7,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143610496","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":"Multi-scale pore network fusion and upscaling of microporosity using artificial neural network","authors":"Abolfazl Moslemipour ,&nbsp;Saeid Sadeghnejad ,&nbsp;Frieder Enzmann ,&nbsp;Davood Khoozan ,&nbsp;Sarah Hupfer ,&nbsp;Thorsten Schäfer ,&nbsp;Michael Kersten","doi":"10.1016/j.marpetgeo.2025.107349","DOIUrl":"10.1016/j.marpetgeo.2025.107349","url":null,"abstract":"<div><div>Digital Rock Physics can significantly enhance our understanding of rock behavior. However, modeling heterogeneous rocks remains challenging because of the trade-off between resolution and field of view. To address this, researchers have developed multi-scale pore network models (PNMs), which integrate PNMs from different scales to create unified multi-scale PNM. Various methodologies exist for merging PNMs from different resolutions, but they often suffer from inaccuracy, high runtime and significant memory consumption, particularly when microporosity is integrated into larger scales. This study introduces a novel fusion and an innovative upscaling approach for efficient multi-scale PNM reconstruction of rocks containing microporosity. Our methods separate resolved and unresolved porosities using different voxel sizes from CT scans at multiple resolutions. Resolved regions have larger voxel sizes, while unresolved areas retain smaller voxel sizes. We extract macro-PNM from the resolved regions and generate stochastic micro-PNM for the unresolved areas. An artificial neural network (ANN), trained on micro-PNM, links micro- and macro-PNMs. The multi-scale PNMs generated using the ANN method had an average permeability of 252 ± 3 mD, closely matching the laboratory-measured permeability of the rock (257 mD). In contrast, the average permeability of multi-scale PNMs reconstructed using the statistical method was significantly higher, at 308 ± 38 mD. Consequently, the ANN-based reconstruction method, owing to the proper connection between scales, improved the accuracy of permeability prediction by approximately 90% compared to the statistical reconstruction method. In the next step, each micro-PNM is upscaled to a base pore based on its effective hydraulic conductance. These base pores are then connected to the macro-PNM using a novel approach. We utilized synchrotron CT images of an Indiana limestone rock at two resolutions as our training dataset. The single- and multi-phase flow analysis of the fused PNM demonstrated excellent agreement with laboratory-measured rock properties. Our upscaling method also reduced runtime by up to 40% (from 312 to 190 CPU-seconds) and memory consumption by approximately 68% (from 25 GB to 8 GB), all without compromising predictive accuracy.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"177 ","pages":"Article 107349"},"PeriodicalIF":3.7,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143592675","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":"Diagenetic evolution in marine carbonate rocks based on the typical case studies: Review and perspectives","authors":"Li Deng ,&nbsp;Chenlin Hu ,&nbsp;Xin Li ,&nbsp;Hongmei Su ,&nbsp;Jonathan Atuquaye Quaye ,&nbsp;Qiuxia Yuan","doi":"10.1016/j.marpetgeo.2025.107352","DOIUrl":"10.1016/j.marpetgeo.2025.107352","url":null,"abstract":"<div><div>Oil and gas derived from marine carbonate rocks are critical energy resources worldwide. The diagenetic process plays a pivotal role in controlling reservoirs, which is essential for understanding reservoir genesis and enhancing oil and gas exploration. Considering the complexity of carbonate rock diagenesis, this review examines the diagenetic mechanisms and stages of marine carbonate rock reservoirs for the first time, with the aim of enhancing the understanding of reservoir evolution and improving oil and gas exploration. This review elucidates the significance of carbonate diagenesis, summarizes the stages of diagenesis, delineates the diagenetic evolution of various types of carbonate rocks, describes the technical methods employed to investigate diagenetic evolution, examines the factors affecting the reservoir, and discusses potential future developments. These findings indicate that compaction, cementation, dissolution, neomorphism, and metasomatism are the primary diagenesis of carbonate rocks. Diagenetic evolution is typically divided into syngenetic, early, intermediate, late, and epigenetic stages. This study employed a basin dynamics perspective to examine the fluid-rock interactions that drive diagenesis. Furthermore, it provided a summary of the diagenesis of microbial and cool-water carbonate rocks. The control of reservoirs through karstification, hydrothermal dissolution, dolomitization, and cementation is dual. In the future, artificial intelligence and artificial neural networks will play significant roles in identifying thin sections and diagenesis. The integration of micro-elements, micro-isotopes, and various techniques is highly significant for studying the diagenetic evolution of carbonate rocks. The storage of CO₂ in marine carbonates is considered a future development trend. This study offers a theoretical basis for the exploration and development of marine carbonates by examining advancements in the diagenetic evolution of marine carbonates, as well as the theoretical and technological aspects.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"176 ","pages":"Article 107352"},"PeriodicalIF":3.7,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143511282","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":"Controls on storage capacity in mudstones. Cementation before sediment compaction and preservation of porosity in lithified rock","authors":"Daniel Minisini,&nbsp;Toni Simo,&nbsp;Joe H.S. Macquaker,&nbsp;Mark D. Rudnicki","doi":"10.1016/j.marpetgeo.2025.107350","DOIUrl":"10.1016/j.marpetgeo.2025.107350","url":null,"abstract":"<div><div>This contribution tackles the origin of porosity and cements in organic-rich mudstones, both important factors in the production of energy resources from unconventional reservoirs. A thorough chronology of sedimentary processes and early diagenesis depicts how most of the porosity (storage capacity) was preserved by 1) bottom current delivery of sand-size coccolith-rich pelagic fecal pellets to the seafloor, 2) limitation of pervasive early calcite cementation by reverse weathering, 3) cementation of pre-compaction microcrystalline quartz that stiffened the rock and limited the compactional porosity loss.</div><div>The presence and chronology of early cements, dissolution fabrics, and migrated oils indicate that significant volumes of fluid flowed through these sediment/rocks, and that fluid transport had a dramatic effect on the evolution of the pore filling histories because much of the cementation occurred prior to compaction. The preservation of porosity due to early cementation enabled subsequent flow of both aqueous and hydrocarbon fluids with consequential impacts on diagenesis and the ability of these mudstones to act as reservoir rather than seal facies.</div><div>The results emphasize that the prediction of facies in organic-rich mudstones should be based on pre-compaction diagenetic processes, which can significantly enhance or occlude porosity. In fact, facies in organic-rich mudstones are not satisfactorily predicted by the traditional methods that investigate solely environments of deposition and sequence stratigraphy.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"177 ","pages":"Article 107350"},"PeriodicalIF":3.7,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143600749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrophysical implications of stromatolite morphologies in the Dam Formation, Saudi Arabia","authors":"Jaber Muharrag ,&nbsp;Hassan A. Eltom ,&nbsp;Fawwaz M. AlKhaldi ,&nbsp;Ammar El-Husseiny ,&nbsp;Fatma Maandouche ,&nbsp;Moaz Salih","doi":"10.1016/j.marpetgeo.2025.107348","DOIUrl":"10.1016/j.marpetgeo.2025.107348","url":null,"abstract":"<div><div>This study examines how stromatolite morphologies influence the porosity and permeability of carbonate strata, focusing on columnar (CF) and laterally linked (LL) forms. By emphasizing the critical role of morphology in shaping porosity, permeability, and pore system architecture, the research integrates field observations with laboratory analyses of 40 core plug samples collected from the Miocene-aged Dam Formation in Saudi Arabia. These analyses include petrographic and Nuclear Magnetic Resonance (NMR) techniques to assess rock texture, laminae characteristics, pore types, and pore size distribution. Porosity and permeability measurements were analyzed in conjunction with detailed rock characterization derived from both field and laboratory data. The findings reveal that both CF and LL stromatolite forms can be classified as coarse-grained stromatolites, comparable to examples from both modern and ancient settings. Both forms exhibit alternating dense, micrite-rich laminae and highly porous, grain-rich laminae. The grain-rich laminae are primarily composed of ooids, peloids, skeletal grains, and quartz, with well-preserved interparticle, intraparticle, and moldic porosity. In contrast, the micrite-rich laminae are characterized by clotted micrite, clotted peloids, and sinuous biofilms preserved on lamina tops. Fenestral and vuggy porosity are present in both lamina types. Despite having relatively narrow porosity ranges—33.93%–48.04% for CF stromatolites and 32.28%–54.90% for LL stromatolites—both forms exhibit wide permeability ranges. Permeability in CF stromatolites ranges from 1.38 mD to 1900.50 mD, whereas LL stromatolites range from 13.31 mD to 2017.78 mD. Notably, LL stromatolites display less variable permeability compared to the highly variable CF forms. Although petrographic and NMR analyses provided valuable insights into the factors influencing permeability, the results demonstrate that these techniques alone cannot fully explain the observed permeability variability especially in the LL form. The findings suggest that additional factors, such as pore connectivity and laminae orientation, might play a significant role in controlling permeability. Proposed scenarios of laminae configuration in the samples suggest that these configurations may be the most critical factor influencing the measured permeability in stromatolites. This research has significant implications for reservoir characterization, providing a deeper understanding of fluid flow behavior in carbonate systems containing stromatolites.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"176 ","pages":"Article 107348"},"PeriodicalIF":3.7,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143509089","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":"Multi-stage dolomitization controlled by sedimentary facies and basement faults: Insights from the Middle Permian Maokou Formation of the Eastern Sichuan Basin, SW China","authors":"Rong Yang ,&nbsp;Xiyan Yang ,&nbsp;Yang Li ,&nbsp;Cunhui Fan ,&nbsp;Yue Li ,&nbsp;Zisang Huang ,&nbsp;Fei Huo ,&nbsp;Xingzhi Wang ,&nbsp;Xiangyu Fan","doi":"10.1016/j.marpetgeo.2025.107334","DOIUrl":"10.1016/j.marpetgeo.2025.107334","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Middle Permian Maokou Formation in China's eastern Sichuan Basin has undergone multiple episodes of dolomitization, recrystallization, and cementation. However, a consensus on the controlling factors for dolomite formation has yet to be reached. This study adopted a multidisciplinary approach, encompassing petrological, geochemical (C-O-Sr stable isotopes, trace elements, and rare earth elements), and fluid inclusion thermometry analyses to determine the spatial distribution characteristics and diagenetic influencing factors of various dolomite types. Core, outcrop, and thin-section observations have identified three types of replacive dolomites and one type of cementing dolomite: very fine crystalline, nonplanar-a to planar-s dolomite (RD1); fine to coarse crystalline, nonplanar-a to planar-s dolomite (RD2-a); fine to coarse crystalline, planar-e dolomite (RD2-b); and medium to coarse crystalline, nonplanar saddle dolomite (CD). All dolomites exhibit more negative δ&lt;sup&gt;13&lt;/sup&gt;C and δ&lt;sup&gt;18&lt;/sup&gt;O values than the host limestone, with &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr ratios exceeding the range of Permian seawater. RD1 has negative or no anomaly in the Eu element and shows higher Sr content with lower Ba content, indicating that it was not affected by hydrothermal fluids. RD2-a and CD show positive anomalies in Eu, with lower Sr content and higher Ba content, indicating that both were affected by hydrothermal fluids. RD2-b, although showing negative or no anomaly in Eu, has fluid inclusion homogenization temperatures comparable to CD and also has less Sr with more Ba, suggesting that its formation also involved hydrothermal fluids. All dolomites exhibit a clear negative anomaly in the Ce element. By synthesizing petrological and geochemical findings, a multi-stage dolomitization model was proposed, which includes seepage-reflux, thermal convection, and hydrothermal dolomitization, reflecting the formation mechanisms of various dolomite types. Before the activation of the basement faults (SQ1 ∼ SQ2-TST), RD1 was formed by limited seepage-reflux dolomitization in low-energy shoals and small-scale confined environments on the periphery of open seas, with dolomitization fluids being contemporary seawater and a small amount of meteoric water. In the early stage of basement fault activity (SQ2-HST), abnormal geothermal temperatures promoted the thermal convection dolomitization between hydrothermal fluids and external cold contemporary seawater in high-energy and low-energy shoals, leading to the formation of RD2-a, with dolomitization fluids being contemporary seawater and a small number of hydrothermal fluids. In the middle stage of basement fault activity (SQ3), silica-rich hydrothermal fluids rose along the faults and mixed with contemporary seawater, replacing the previously formed dolostones and host limestone to form RD2-b. In the peak stage of basement fault activity (the end of Guadeloupe), deep hydrothermal fluids were fully tra","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"176 ","pages":"Article 107334"},"PeriodicalIF":3.7,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534602","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}