Marine and Petroleum Geology最新文献

{"title":"A multi-proxy approach to explore paleoenvironmental oscillations and chronostratigraphy of Thanetian carbonates in Eastern Tethys, Pakistan","authors":"Amir Shahzad ,&nbsp;Yasir Sirfraz ,&nbsp;Khawaja Shoaib Ahmed ,&nbsp;Muhammad Hanif ,&nbsp;Muhammad Tayyib Riaz ,&nbsp;Khawaja Shafique Ahmad ,&nbsp;Thierry Adatte","doi":"10.1016/j.marpetgeo.2024.107169","DOIUrl":"10.1016/j.marpetgeo.2024.107169","url":null,"abstract":"<div><div>This study is the first to incorporate geochemical analyses alongside traditional micropaleontological and sedimentological methods to redefine the chronostratigraphy, paleoenvironmental history and regional correlation of the Late Paleocene Lockhart Limestone from four distinct sections covering the entire Upper Indus Basin. Based on the age diagnostic foraminiferal species, we report SBZ3 to SBZ4 (Thanetian age) for the Lockhart Limestone in contrast to previous studies restricting it to SBZ3. The interpretation of eight distinct microfacies reveals a progressively shallowing upward sequence, indicating a dynamic depositional environment with varying energy levels and water depths ranging from inner, middle, to outer ramp settings. Mineralogically, the formation is predominantly composed of calcite, with quartz being the next significant component. Geochemical analyses, specifically the major oxide results, highlight that CaO is the primary constituent, while notable amounts of SiO₂, Fe₂O₃, Al₂O₃, and MgO are present. The low proportions of SiO₂ and Al₂O₃, combined with their negative correlation with CaO, and high Mg/Ca ratio suggest limited siliciclastic input during the precipitation of limestone that supports the shallow marine depositional environment inferred from the facies analysis. Trace elemental ratios, indicating predominantly oxic conditions, also align with the well-oxygenated waters of a shallow marine setting. Paleosalinity and paleotemperature indicators suggest normal marine and moderate paleotemperature conditions for limestone facies, with lagoonal conditions for shale facies, which is consistent with the interpreted shallow marine environment. The low Total Organic Carbon (TOC) content indicates the presence of type-III and IV organic matter, derived from recycling or continental sources, suggesting limited organic matter preservation in the depositional setting. The clay mineralogy suggests mainly humid conditions with occasional warm climates and alternating humid and arid periods. The deposition of the marine facies of Lockhart Limestone marks the transgression of the Eastern Tethys following a regressive episode that deposited the continental facies of the Hangu Formation, influenced by evolving paleoclimate and geomorphology under Paleo-Tethys tectonism.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107169"},"PeriodicalIF":3.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656661","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":"Disentangling and interpreting nonlinear molecular and isotopic variations in petroleum using machine learning","authors":"Keyu Tao ,&nbsp;Jian Cao ,&nbsp;Yuce Wang ,&nbsp;Wanyun Ma","doi":"10.1016/j.marpetgeo.2024.107175","DOIUrl":"10.1016/j.marpetgeo.2024.107175","url":null,"abstract":"<div><div>Nonlinear variations in the molecular and isotopic compositions of phases in complex geosystems greatly hinder the application of geochemical proxies. This study aims to disentangle the implicit nonlinear mathematical structures embedded in geochemical datasets, effectively disaggregating overlapping geological influences that drive the intricate variations in the geochemical signatures of phases. Employing a typical hybrid petroleum system as a case study, we utilize an unsupervised machine learning algorithm to visualize the effects of source disparities and distinct evolutionary processes, such as mixing, thermal maturation, biodegradation, and evaporative fractionation, on the molecular compositions among crude oils. We further investigate the regression relationship between molecular composition and bulk <em>δ</em>¹³C signal in petroleum. Our findings reveal that by decomposing the regression model to solely reflect a specific dominant influence, the model could provide a precise geological interpretation. Accordingly, we unravel the subtle variations and underlying mechanisms of carbon isotopic fractionation in petroleum substances from different origins under the impact of maturation. Our results underscore the substantial potential of strategically applied machine learning techniques in reconstructing the geochemical evolution of complex geosystems, advocating for their broader application.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107175"},"PeriodicalIF":3.7,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529293","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":"Thermochronological constraints on the evolution of the Bongor Basin, Chad","authors":"Ruxin Ding ,&nbsp;Li Wang ,&nbsp;Kunye Xiao ,&nbsp;Yangshijia Li ,&nbsp;Jie Hu ,&nbsp;Yebo Du ,&nbsp;Yu Yang ,&nbsp;Xinshun Zhang ,&nbsp;Lirong Dou","doi":"10.1016/j.marpetgeo.2024.107165","DOIUrl":"10.1016/j.marpetgeo.2024.107165","url":null,"abstract":"<div><div>The Bongor Basin is an important petroliferous basin in the Western and Central African rift system. The basin's evolution history is featured with a strong tectonic inversion during the Late Cretaceous, which resulted in its unique basin structure and hydrocarbon accumulation pattern. However, due to the complex process of repeated cooling and heating, single sample bedrock thermochronology can hardly provide accurate constraints to its thermal evolution history. In this paper, nine granitic core samples from the crystalline basement in five wells on the northern slope of the Bongor Basin were analyzed using multiple thermochronological methods (apatite U-Th/He, apatite fission tracks and length distribution, apatite U-Pb dating) as well as vertical profiles to obtain a more accurate thermal history. The results show that the samples from all five wells underwent four stages of thermal history: from ∼600 Ma to 135 Ma, the samples cooled continuously from 600 °C to near-surface temperatures; from ∼135 Ma to 100 Ma, the samples were heated rapidly; from 100 Ma to 60–80 Ma, the samples cooled rapidly; and after that, the samples experienced slow differential heating and cooling. The thermal history results show that the key time for the strong inversion of the Bongor Basin was between 80 and 90 Ma when the basin was uplifted and exhumed as a whole, while samples in different fault blocks underwent differential uplift and subsidence since the Paleogene.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107165"},"PeriodicalIF":3.7,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572729","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":"Seismic stratigraphy and petroleum prospectivity in the Northern Rovuma Basin, offshore Tanzania","authors":"Emily Barnabas Kiswaka ,&nbsp;Dicky Harishidayat ,&nbsp;Oras Joseph Mkinga ,&nbsp;Evelyne Mbede ,&nbsp;Elisante E. Mshiu ,&nbsp;Cassy Mtelela","doi":"10.1016/j.marpetgeo.2024.107173","DOIUrl":"10.1016/j.marpetgeo.2024.107173","url":null,"abstract":"<div><div>The upper slope area of the Northern Rovuma Basin has been poorly studied and little is known about its development and petroleum prospectivity. Interpretation of wellbore, 2D and 3D seismic reflection data in this area has allowed identification of seismic features reflecting key factors for understanding the development of the Cretaceous-Holocene stratigraphy and distribution of petroleum system elements. Our results show that infill of sediment into the basin was due to an interplay of three major factors. These are the sea level variations, extensional tectonics and sediment gravity flows. The Miocene and Pleistocene-Holocene tectonic events triggered gravity flows that supplied sediments to the basin. The resultant deposits include slides, slumps, debrites and turbidites some of which contain potential reservoirs that are interpreted to have been charged by the Permo-Triassic Karoo shales and Cretaceous-Cenozoic source rocks. These reservoirs are contained in both stratigraphic and structural traps with localized combinations in some places, and are encased by deep marine shales. Some of the potential reservoirs are positively inverted and compartmentalized, and they contain several bright and flat spots suggesting hydrocarbon accumulations within the Miocene and Oligocene intervals. It has also been revealed that major gravity flows and bottom currents, that supplied and distributed sediment to the basin, were confined in three long-lived channelized systems that were initiated during the Cretaceous (due to rapid regression), and the Oligocene and Pleistocene periods (due to rapid uplift). The channels migrated toward the southeast, with some shift toward the northeast, and had overall northeast traverse direction perpendicular to the shoreline. The reported gravity flows eroded previously deposited sediment in most places causing several unconformities in the whole Cretaceous-Holocene stratigraphy. Seismic stratigraphic interpretation and facies analysis have proved useful in the identification of key petroleum system elements and improve understanding of sedimentary fill evolution of the study area.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107173"},"PeriodicalIF":3.7,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529210","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":"Structural evolution of the Handun salt diapir, Zagros fold and thrust belt, southern Iran","authors":"Marco Snidero,&nbsp;Josep Anton Muñoz,&nbsp;Pablo Santolaria,&nbsp;Nuria Carrera,&nbsp;Mireia Butille","doi":"10.1016/j.marpetgeo.2024.107172","DOIUrl":"10.1016/j.marpetgeo.2024.107172","url":null,"abstract":"<div><div>The Fars region, in the Zagros fold and thrust belt, hosts a wide range of diapirs piercing over 10 km of stratigraphic sequence. Comprising Precambrian to Early-Cambrian Hormuz Salt, these diapirs exhibit a prolonged history of evolution. Outcrop evidence for understanding the diapir deformation history is mostly limited to the Cenozoic contractive phase, and the seismic data lacks the necessary quality for an exhaustive understanding of the deepest structure's geometries. Through regional and field evidence we unravel the Handun salt structure evolution and propose a sequential restoration to describe the key deformational events. Our study presents a field-based novel regional balanced cross-section and a 3D-geological model, and addresses the role of structural inheritances and the position of the Handun diapir with respect to the decupled basement. The performed field studies describe folds and unconformities related to Cenozoic halokinetic sequences with exceptional clarity. It was possible to observe changes of the diapir activity along the structure and provide field evidence for the relative timing and kinematics of primary and secondary welding. Finally, our data suggest that the Handun diapir formed in the early Paleozoic above the shoulder of a basement extensional fault, and was partially translated above its southern hanging-wall during the shortening. In the Paleocene a sustained ratio of salt rise rate was enhanced by the Zagros/Oman contraction. In response to the Oligocene continental collision, the diapir was profusely supplied with salt, which flared upward to form overhangs. Since the middle Miocene the salt supply slowly depleted, with the diapiric walls remaining near the surface but tapering upward, probably due to primary welding or increased sedimentation. Secondary welding occurred post-Pliocene in the last stages of the diapir evolution with consequent development of a secondary minibasin.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107172"},"PeriodicalIF":3.7,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529211","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":"Influence of Triassic and Jurassic arc magmatism in Lower Jurassic Sierra de Santa Rosa Formation, northwestern México: Constraints from geochemistry and U-Pb geochronology","authors":"Jocelyn Galindo-Ruiz ,&nbsp;Erik Ramírez-Montoya ,&nbsp;Jayagopal Madhavaraju ,&nbsp;Carlos M. González-León ,&nbsp;Francisco J. Grijalva-Noriega ,&nbsp;Luigi Solari ,&nbsp;Rogelio Monreal ,&nbsp;Inocente G. Espinoza-Maldonado","doi":"10.1016/j.marpetgeo.2024.107168","DOIUrl":"10.1016/j.marpetgeo.2024.107168","url":null,"abstract":"<div><div>The Permo-Triassic and Lower Jurassic sedimentary succession of the El Antimonio Group in northern Sonora, Mexico is inferred to be deposited in a forearc basin and its age has been constrained by fossil assemblages and detrital zircon geochronology. In this work, petrography, geochemistry and detrital zircon U-Pb geochronology were undertaken on the Sierra de Santa Rosa Formation, the younger unit of the El Antimonio Group in the locality of the Sierra del Álamo, to constrain its tectonic setting, age, source area paleoweathering, and provenance. Sandstone of Sierra de Santa Rosa Formation is petrographically classified as arkose. The elemental ratios, REE patterns and Eu anomaly, as well as bivariate and ternary plots suggest igneous felsic sources subjected to weak to moderated chemical weathering under arid climatic conditions for detritus of the Sierra de Santa Rosa Formation. Detrital zircon U-Pb geochronology of seven sandstone samples of this unit record main populations of Proterozoic age (58% of the total grains) with age peaks at 1.68. 1.39 and 1.14 Ga and Triassic age (31% of total grains) with age peak at 219 Ma, and subordinate groups of Paleozoic, Jurassic and Archean ages. Main sources for the zircon grains are the regional nearby igneous-metamorphic Proterozoic basement rocks, recycled detritus from the Proterozoic and Paleozoic sedimentary cover, and the Permo-Triassic and Jurassic continental magmatic arcs of southwestern North America. The detrital zircon U-Pb geochronology of the dated samples allows to establish Sinemurian to early Toarcian maximum depositional ages for the Sierra de Santa Rosa Formation in the locality of the Sierra del Álamo.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107168"},"PeriodicalIF":3.7,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142560809","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":"Tectono-sequence evolution of an extensional strike-slip composite basin, a case study of the Miaoxi'nan sub-sag in the eastern Bohai Bay Basin","authors":"Sheng Fu ,&nbsp;Haifeng Yang ,&nbsp;Lijun Song ,&nbsp;Wei Zhou ,&nbsp;Jiawang Ge ,&nbsp;Yanqin Guo","doi":"10.1016/j.marpetgeo.2024.107170","DOIUrl":"10.1016/j.marpetgeo.2024.107170","url":null,"abstract":"<div><div>The significance of tectonics in shaping sequence stratigraphy within continental rift basins, especially those with extensional strike-slip composite characteristics, cannot be overstated. These basins, often repositories of rich oil and gas reserves, are defined by their intricate fault systems and dynamic tectonic interplay. Despite their economic importance, the tectono-sequence characteristics of these basins remain underexplored, affecting the understanding and prediction of petroleum systems. This study presents a comprehensive tectono-sequence analysis of the Miaoxi'nan sub-sag in the eastern Bohai Bay Basin, a continental lacustrine sag intersected by the eastern branch of the Tan-Lu fault zone. By integrating extensive 3D seismic data, wireline logs, and previous research, we establish a detailed tectono-sequence framework and unravel the complex interplay of geometric and kinematic characteristics within the extensional strike-slip fault system that governs the evolution of the basin. Our investigation reveals a multi-tiered sequence stratigraphic structure comprising two first-order, 4 s-order, and seven third-order sequences. The west sub-branch of the East branch of the Tan-Lu fault zone (EB-TLFZ) is identified as a strike-slip fault with a predominantly south-north strike, while the east sub-branch exhibits characteristics of a persistent tension-shear strike-slip fault zone. The study also shows a transitional fault strike of the rifting system from a multi-directional orientation at the base to a northeast-northeast-east direction, corresponding with different tectonic stages that have directed fault activities and sedimentary deformation. Additionally, both the extensional and strike-slip fault systems of the sag have experienced segmental growth evolution, influencing the westward and northward migration patterns of the basin's depocenter and subsiding center. Overall, the sequence development within the Miaoxi'nan sub-sag is predominantly regulated by the first- and second-order extensional faults, with the EB-TLFZ sub-branch faults providing further adjustment. This study provides vital insights into the tectono-sequence dynamics of extensional strike-slip composite basins, with implications for future hydrocarbon exploration and exploitation.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107170"},"PeriodicalIF":3.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529294","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":"Depositional architecture and evolution of Quaternary submarine canyon-fan system in the Baiyun Sag of the Pearl River Mouth Basin, northern South China Sea","authors":"Zhixuan Lin ,&nbsp;Ming Su ,&nbsp;Haiteng Zhuo ,&nbsp;Hui Chen ,&nbsp;Jiapeng Jin ,&nbsp;Shuqin Huang ,&nbsp;Zhina Wang","doi":"10.1016/j.marpetgeo.2024.107167","DOIUrl":"10.1016/j.marpetgeo.2024.107167","url":null,"abstract":"<div><div>Submarine canyons in the shelf margin usually serve as essential conduits for delivering sediments to slopes and basins and coevally develop turbidite reservoirs within deep-water fan systems. To understand the control of the evolution of the canyon-fan system, we focused on Quaternary deep-water depositional systems imaged in 3D seismic reflection data covering the lower reaches of the canyons and the base of the slope in the Baiyun Sag, on the northern margin of the South China Sea. By analyzing seismic facies tied to seismic attribute maps and time-thickness variations, three main seismic units were interpreted and described with markedly different geomorphologies and facies assemblages. Variations in the depositional architecture of the fan system recorded changes in sediment conditions during the Quaternary. The evolution of the Quaternary canyon-fan system can be summarized in three stages. Stage 1 is characterized by fan complexes with backstepping and stratigraphic onlapping against the erosional base, indicating a reduction in sediment supply due to rapid transgression during the Early Pleistocene. During Stage 2, the sediment supply decreased to its lowest rate, producing elongate-shaped turbidite complexes and a high proportion of hemipelagic deposits. In contrast, stage 3 was expressed by canyon-fan systems with downlapping stratigraphy resulting from the enhancement of sediment input during shelf margin/slope progradational intervals. The Quaternary canyon-fan system evolution was controlled not only by the rapid transgression but also by the efficiency of the sediment transfer mechanisms. Although higher rate of sediment supply occurred during stage 1, the dominant canyon-direct fed systems at this stage had highly efficient sediment transfer mechanisms, generating thicker and larger canyon-fan systems compared to stage 3. During stage 3, the progradation-direct-fed system became the primary sediment transport pattern causing sediment to mostly accumulate on the slope and reduce sediment delivery to the basin floor. Our results indicate that the distribution of gas hydrate accumulation is strongly associated with the depositional pattern of turbidites within the Lower Pleistocene succession.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"170 ","pages":"Article 107167"},"PeriodicalIF":3.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537974","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 and carbon isotopic geochemistry of oils with different fluorescence color from the Upper Jurassic Qigu formation and oil accumulation process in Yongjin area, Junggar Basin in China","authors":"Hongrui Zhang ,&nbsp;Hua Liu ,&nbsp;Wanglu Jia ,&nbsp;Hui Tian ,&nbsp;Jinbu Li ,&nbsp;Shuang Yu ,&nbsp;Yansheng Qu ,&nbsp;Xiangyu Meng","doi":"10.1016/j.marpetgeo.2024.107163","DOIUrl":"10.1016/j.marpetgeo.2024.107163","url":null,"abstract":"<div><div>The Yongjin area, located in the middle of the Junggar Basin, is an important oil-producing region. Its major oil-producing formation is the Upper Jurassic Qigu Formation, which has experienced multiple oil-charging events that have resulted in oils with various fluorescent colors. However, the source of oils from the Qigu Formation is currently debated. As exploration and development progressed, the productivity of the Qigu Formation was observed to vary owing to oil viscosity differences. Conventional extraction methods can only be used to obtain a mixture of fluorescing oils of different colors, making it difficult to analyze the properties of oils that charge during different periods. Using microscopy to observe fluorescence the characteristics of oil in various samples were analyzed. Then, accelerated sequential extraction was used to separate the oils with different fluorescent colors (Groups I–IV). Through GC-MS (gas chromatography), GC-IRMS (gas chromatography-mass spectrometry), FT-IR (fourier transform infrared spectroscopy), and fluid inclusion observations and measurements, in conjunction with the geological context, the sources of oils from different charge periods and genesis of heavy oil were determined and the process of oil accumulation was reconstructed. Three stages of oil charging were identified: (1) During the Middle to Late Jurassic, low-mature and mature oil from the Lower Permian Fengcheng Formation and a low quantity of low-mature oil from the Middle Permian Lower Wuerhe Formation charged the Qigu Formation. These oils underwent notable biodegradation and oxidation, with some captured by inclusions (Group III) for preservation. (2) During the Late Cretaceous to Early Paleogene, mature oil from the Wuerhe Formation charged the Qigu Formation. This oil mixed with early oil that was not captured by the inclusions, resulting in the formation of black-brown fluorescing oil (Group IV) and yellow fluorescing inclusion oil (Group II). (3) From the Late Paleogene to the present, highly mature condensates from the Lower Wuerhe Formation charged the Qigu Formation. The oil mixed with early oil to generate yellow-brown (Group II) and blue-white (Group I) fluorescing oils. Low-mature and mature oil from the Fengcheng Formation charged the Jurassic reservoirs and underwent secondary alteration, whereas high-mature oil and gas did not. These oils likely predominantly accumulated in reservoirs between the Fengcheng and Lower Wuerhe formations. Although the Jurassic source rocks began to generate oil, this oil did not migrate upward to the Qigu Formation, indicating that the conventional and unconventional reservoirs under the Jurassic Qigu Formation have exploration potential.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107163"},"PeriodicalIF":3.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579075","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":"Do red marine carbonates represent oxic environments? New understanding from the Upper Ordovician marine limestone in Tarim Basin, China","authors":"Mu Liu ,&nbsp;Daizhao Chen ,&nbsp;Haoran Ma ,&nbsp;Yi Ding","doi":"10.1016/j.marpetgeo.2024.107166","DOIUrl":"10.1016/j.marpetgeo.2024.107166","url":null,"abstract":"<div><div>Marine red beds (MRBs), typically colored by Fe- and Mn-rich minerals, are often interpreted as indicators of bottom water oxygenation. However, their continuous formation requires long-term input of aqueous derived Fe-Mn oxides and/or stable sources of Fe²⁺ and Mn²⁺ ions, challenging the traditional concept of “red equals oxic environment.” This study investigates two coeval Upper Ordovician Sandbian MRB carbonate intervals in the Tarim Basin. Previous studies attributed the pigment origin to hematite. Th/U values and total rare earth element and yttrium (REY) contents increased in the MRB interval, indicating a terrestrial source of iron. Hematite was observed within the intercrystal pores of calcite precipitating from porewater, consistent with high Ni_carb abundance and MREE-enriched bulge pattern in the red intervals. Both sections exhibit high Fe_carb and Mn_carb, pointing to substantial reductive dissolution of Fe and Mn oxides. Simulation shows that isotopic discrimination (Δ¹³C) between carbonate and organic carbon could be biased by increasing benthic Fe-Mn flux, leading to decreased Δ¹³C values in MRB intervals. Ce/Ce∗ values in the high-Mn_carb interval reflect the releasing of Ce by reductive dissolution of Mn oxides. The commonly used carbonate-based redox proxy I/(Ca + Mg) ratio is correlated positively with Mn_carb in the shallower section and with TOC in the deeper section, while it is negatively correlated with TOC in the shallower horizon, suggesting that iodine behavior may be influenced by adsorption and releasing of Mn hydro-oxides and organic matter besides oxygen contents. This study links MRB coloring to Fe and Mn mineral cycling in pore water through reductive dissolution and oxidative precipitation, and highlights potential biases of carbonate-based redox proxies that might be susceptible to other electron acceptors/donors such as Fe-Mn oxides and organic matter, in addition to free oxygen in seawater.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107166"},"PeriodicalIF":3.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529212","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}