Pub Date : 2025-01-15DOI: 10.1016/j.marpetgeo.2025.107291
Gabriel M. Marins , Nicholas M. Lima , Leonardo C. Oliveira , Adriana O. Gangá , Carlos M. Monnerat de Oliveira , Ygor M. Rocha , Francisco Abrantes , Lucas M.M. Rossetti , Juliana Costa , John M. Millet , Sofia A. Fornero , Sandra A. Iwata
<div><div>The carbonate reservoirs of the Mero field in the Santos Basin were intruded during the Upper Cretaceous by a series of alkaline basalt composition diabase dikes and sills. Despite the field's significance as one of Brazil's leading oil producers, the roots, migration, evolution, and emplacement mechanisms of this magmas in the reservoirs remain poorly understood. This study aims to contribute to the understanding of this phenomenon by presenting novel results based on seismic analysis and the only available core samples of two diabase intrusions from this event and their respective carbonate reservoir host rocks in Mero field. The two sills sampled by well 3-BRSA-1322-RJS are emplaced at the top of the Barra Velha Formation and represent segments of the same sheet intrusion. The roots of these intrusive bodies are associated with a complex plumbing system concentrated within lithospheric discontinuities, specifically the Mohorovičić (Moho). The NNW-SSE orientation of the studied sheet intrusion and of some of the underlying dikes indicate a structural control by deep basement faults with the same orientation, reactivated during the rifting phase and Upper Cretaceous. The emplacement mechanism of the sheet intrusion within the reservoir carbonates appears to be controlled by stratigraphic factors. The magma preferentially intrudes the rudstone/laminite contacts and laminite layers of the Lula's Fingers stratigraphic marker (LFSM). The high-temperature of this igneous body (1088–1158 °C) induced the cracking of organic matter within the host rock, leading to the production of liquid and gaseous hydrocarbons. Localized fractures within the diabases filled with bitumen indicate also the presence of hydrocarbon storage within these rocks. The segmentation of the sheet intrusion within laminite is attributed to the fissility of this rock and the formation of fractures in the magmatic front during the rapid maturation of organic matter. The mushroom-like morphology of the intrusion reflects the lateral migration of magma along the LFSM that cover a carbonate high (mound) in the NE of Mero Field. The segmentation of this intrusive body locally compartmentalizes the reservoir of the Mero field into "box-work" blocks impacting their connectivity. Geochemical evidence and textural features indicate that the sill was replenished by multiple pulses of alkaline basaltic melt from the same magma reservoir. The emplaced magma evolved through fractional crystallization, resulting in the formation of net-veined complexes composed of residual trachytic materials. The high concentrations of anorthoclase in these magmatic residues result in a positive peak in the gamma-ray log along the intrusions. The findings presented in this study elucidate the intricate evolution of these magmas from their ascent to their emplacement in the pre-salt carbonates. Additionally, they offer novel perspectives on the potential impacts of these magmas on the host rocks and t
{"title":"The deep roots and emplacement of Santonian intrusions in the Pre-Salt reservoirs of the Mero Field, Santos Basin, Brazil","authors":"Gabriel M. Marins , Nicholas M. Lima , Leonardo C. Oliveira , Adriana O. Gangá , Carlos M. Monnerat de Oliveira , Ygor M. Rocha , Francisco Abrantes , Lucas M.M. Rossetti , Juliana Costa , John M. Millet , Sofia A. Fornero , Sandra A. Iwata","doi":"10.1016/j.marpetgeo.2025.107291","DOIUrl":"10.1016/j.marpetgeo.2025.107291","url":null,"abstract":"<div><div>The carbonate reservoirs of the Mero field in the Santos Basin were intruded during the Upper Cretaceous by a series of alkaline basalt composition diabase dikes and sills. Despite the field's significance as one of Brazil's leading oil producers, the roots, migration, evolution, and emplacement mechanisms of this magmas in the reservoirs remain poorly understood. This study aims to contribute to the understanding of this phenomenon by presenting novel results based on seismic analysis and the only available core samples of two diabase intrusions from this event and their respective carbonate reservoir host rocks in Mero field. The two sills sampled by well 3-BRSA-1322-RJS are emplaced at the top of the Barra Velha Formation and represent segments of the same sheet intrusion. The roots of these intrusive bodies are associated with a complex plumbing system concentrated within lithospheric discontinuities, specifically the Mohorovičić (Moho). The NNW-SSE orientation of the studied sheet intrusion and of some of the underlying dikes indicate a structural control by deep basement faults with the same orientation, reactivated during the rifting phase and Upper Cretaceous. The emplacement mechanism of the sheet intrusion within the reservoir carbonates appears to be controlled by stratigraphic factors. The magma preferentially intrudes the rudstone/laminite contacts and laminite layers of the Lula's Fingers stratigraphic marker (LFSM). The high-temperature of this igneous body (1088–1158 °C) induced the cracking of organic matter within the host rock, leading to the production of liquid and gaseous hydrocarbons. Localized fractures within the diabases filled with bitumen indicate also the presence of hydrocarbon storage within these rocks. The segmentation of the sheet intrusion within laminite is attributed to the fissility of this rock and the formation of fractures in the magmatic front during the rapid maturation of organic matter. The mushroom-like morphology of the intrusion reflects the lateral migration of magma along the LFSM that cover a carbonate high (mound) in the NE of Mero Field. The segmentation of this intrusive body locally compartmentalizes the reservoir of the Mero field into \"box-work\" blocks impacting their connectivity. Geochemical evidence and textural features indicate that the sill was replenished by multiple pulses of alkaline basaltic melt from the same magma reservoir. The emplaced magma evolved through fractional crystallization, resulting in the formation of net-veined complexes composed of residual trachytic materials. The high concentrations of anorthoclase in these magmatic residues result in a positive peak in the gamma-ray log along the intrusions. The findings presented in this study elucidate the intricate evolution of these magmas from their ascent to their emplacement in the pre-salt carbonates. Additionally, they offer novel perspectives on the potential impacts of these magmas on the host rocks and t","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"174 ","pages":"Article 107291"},"PeriodicalIF":3.7,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177560","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}
Pub Date : 2025-01-15DOI: 10.1016/j.marpetgeo.2025.107292
Yang Gao , Lin Jiang , Weiyan Chen , Hongkui Dong , Wen Zhao , Fujie Jiang , Qingong Zhuo , Haizu Zhang , Yao Hu , Zhou Fang , Xiaohao Wang , Yingqi Feng
In recent years, as oil and gas exploration has increasingly advanced into deeper layers, the tectonic evolution of the Tarim Basin before the Mesozoic has garnered significant attention. However, due to the scarcity of magmatic and metamorphic records within the basin, analyses of major tectonic events remain contentious. Orogenic events contribute substantial detrital material to nearby regions, which is consequently reflected in the detrital zircon record. This study focuses on the sedimentary strata of the central uplift zone of the Tarim Basin. U-Pb dating was conducted on 600 detrital zircon grains from the Silurian to the Carboniferous periods, revealing two main age peaks at 806Ma and 452Ma. No significant peaks were observed in the age distribution outside of these two regions. The Paleozoic zircon data obtained from this study, when combined with previously published U-Pb age data of 2155 detrital zircons from southern and northern Tarim, indicate that these ages do not correlate with the Grenville orogeny event occurring between 1300Ma and 900Ma. Thus, the impact of the Grenville orogeny on the Tarim Craton appears to be very limited. The peak around 800 Ma generated by all zircon data corresponds to the transition period from the breakup of the Rodinia supercontinent to the formation of Gondwana. The collisional assembly of the north and south Tarim terranes likely occurred between 900 and 820Ma, during which the collisional orogeny led to the formation of the central uplift zone in Tarim. In the Paleozoic, the sediment sources of the central uplift zone in Tarim primarily originated within Tarim itself, with additional influences from the West Kunlun orogenic belt, South Tianshan, and Altun orogenic belt.
{"title":"The tectonic evolution of the pre-Mesozoic key period in the Tarim Basin: Constraints from U-Pb geochronology of paleozoic detrital zircons in the central uplift zone","authors":"Yang Gao , Lin Jiang , Weiyan Chen , Hongkui Dong , Wen Zhao , Fujie Jiang , Qingong Zhuo , Haizu Zhang , Yao Hu , Zhou Fang , Xiaohao Wang , Yingqi Feng","doi":"10.1016/j.marpetgeo.2025.107292","DOIUrl":"10.1016/j.marpetgeo.2025.107292","url":null,"abstract":"<div><div>In recent years, as oil and gas exploration has increasingly advanced into deeper layers, the tectonic evolution of the Tarim Basin before the Mesozoic has garnered significant attention. However, due to the scarcity of magmatic and metamorphic records within the basin, analyses of major tectonic events remain contentious. Orogenic events contribute substantial detrital material to nearby regions, which is consequently reflected in the detrital zircon record. This study focuses on the sedimentary strata of the central uplift zone of the Tarim Basin. U-Pb dating was conducted on 600 detrital zircon grains from the Silurian to the Carboniferous periods, revealing two main age peaks at 806Ma and 452Ma. No significant peaks were observed in the age distribution outside of these two regions. The Paleozoic zircon data obtained from this study, when combined with previously published U-Pb age data of 2155 detrital zircons from southern and northern Tarim, indicate that these ages do not correlate with the Grenville orogeny event occurring between 1300Ma and 900Ma. Thus, the impact of the Grenville orogeny on the Tarim Craton appears to be very limited. The peak around 800 Ma generated by all zircon data corresponds to the transition period from the breakup of the Rodinia supercontinent to the formation of Gondwana. The collisional assembly of the north and south Tarim terranes likely occurred between 900 and 820Ma, during which the collisional orogeny led to the formation of the central uplift zone in Tarim. In the Paleozoic, the sediment sources of the central uplift zone in Tarim primarily originated within Tarim itself, with additional influences from the West Kunlun orogenic belt, South Tianshan, and Altun orogenic belt.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107292"},"PeriodicalIF":3.7,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147882","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}
Pub Date : 2025-01-11DOI: 10.1016/j.marpetgeo.2025.107288
Sergei Lazarev , Oleg Mandic , Marius Stoica , Pavel Gol'din , Stjepan Ćorić , Mathias Harzhauser , Wout Krijgsman , Dias Kadirbek , Davit Vasilyan
The hydrological connectivity of semi-isolated basins with the global ocean drives remarkable ecosystem turnover and regional climate shifts, making palaeoenvironmental and palaeohydrological studies of the epicontinental basins of high relevance. During the late Middle–Late Miocene, the Paratethys Sea, which occupied vast areas of the West Eurasian Interior, underwent a notable hydrological isolation from the global ocean. Between 12.65 and 7.65 Ma, the Paratethys experienced significant water level fluctuations and eventually near-total ecosystem collapse. The causes and timing of these hydrological and biotic changes remain unclear, especially in the understudied Caspian Sea region. Our study presents an integrated stratigraphic framework of the 136-m-thick Karagiye section on the east coast of the Caspian Sea (Mangystau region, Kazakhstan). The fauna-rich deposits document the pre- (Konkian), syn- (Volhynian, Bessarabian and Khersonian) and post-isolation (Maeotian) phases of Paratethys evolution at its eastern margin. We reconstruct the palaeoenvironmental history of the Caspian Basin by combining palaeomagnetic dating with biostratigraphic analyses of microfauna, molluscs, marine vertebrates and calcareous nannoplankton. Our key findings in the studied section include: 1. Konkian (incomplete): Open lagoonal environments with restricted connectivity to the global ocean in the early Konkian followed by a middle Konkian faunal influx and establishment of normal marine environments; 2. Volhynian (incomplete, 12.3–12.05 Ma): Onset of Paratethys hydrological isolation with marginal lagoonal environments, new endemic species, plus rare surviving Konkian taxa; 3. Bessarabian (12.05–9.9 Ma): Transgression and offshore setting at ∼12.05 Ma with maximum flooding at 11.6 Ma and Intra-Bessarabian Carbonate Surge at ∼10.7 Ma, followed by upper Bessarabian (10.7–9.9 Ma) carbonate platform interior settings; 4. Khersonian (9.9–7.65 Ma): Khersonian Ecological Crisis, carbonate platform to backshore environments with hiatus between 9.5 and ∼8.0 Ma representing an extreme lowstand. 5. Maeotian (incomplete 7.65–7.0 Ma): Transgression at 7.65 Ma, followed by a delayed invasion of Maeotian faunas at 7.5 Ma, linked to the reconnection of the Caspian Basin with the rest of the Eastern Paratethys. The well-dated biotic record of Karagiye enhances understanding of Paratethyan hydrological and ecological events in the Caspian Basin and provides a foundation for further palaeoclimatic and palaeobiogeographic studies across Eurasia.
{"title":"Hydrological isolation of the Paratethys in the late Middle-Late Miocene: Integrated stratigraphy, palaeoenvironments and biotic record of the Caspian Basin, Karagiye, Kazakhstan","authors":"Sergei Lazarev , Oleg Mandic , Marius Stoica , Pavel Gol'din , Stjepan Ćorić , Mathias Harzhauser , Wout Krijgsman , Dias Kadirbek , Davit Vasilyan","doi":"10.1016/j.marpetgeo.2025.107288","DOIUrl":"10.1016/j.marpetgeo.2025.107288","url":null,"abstract":"<div><div>The hydrological connectivity of semi-isolated basins with the global ocean drives remarkable ecosystem turnover and regional climate shifts, making palaeoenvironmental and palaeohydrological studies of the epicontinental basins of high relevance. During the late Middle–Late Miocene, the Paratethys Sea, which occupied vast areas of the West Eurasian Interior, underwent a notable hydrological isolation from the global ocean. Between 12.65 and 7.65 Ma, the Paratethys experienced significant water level fluctuations and eventually near-total ecosystem collapse. The causes and timing of these hydrological and biotic changes remain unclear, especially in the understudied Caspian Sea region. Our study presents an integrated stratigraphic framework of the 136-m-thick Karagiye section on the east coast of the Caspian Sea (Mangystau region, Kazakhstan). The fauna-rich deposits document the pre- (Konkian), syn- (Volhynian, Bessarabian and Khersonian) and post-isolation (Maeotian) phases of Paratethys evolution at its eastern margin. We reconstruct the palaeoenvironmental history of the Caspian Basin by combining palaeomagnetic dating with biostratigraphic analyses of microfauna, molluscs, marine vertebrates and calcareous nannoplankton. Our key findings in the studied section include: 1. Konkian (incomplete): Open lagoonal environments with restricted connectivity to the global ocean in the early Konkian followed by a middle Konkian faunal influx and establishment of normal marine environments; 2. Volhynian (incomplete, 12.3–12.05 Ma): Onset of Paratethys hydrological isolation with marginal lagoonal environments, new endemic species, plus rare surviving Konkian taxa; 3. Bessarabian (12.05–9.9 Ma): Transgression and offshore setting at ∼12.05 Ma with maximum flooding at 11.6 Ma and Intra-Bessarabian Carbonate Surge at ∼10.7 Ma, followed by upper Bessarabian (10.7–9.9 Ma) carbonate platform interior settings; 4. Khersonian (9.9–7.65 Ma): Khersonian Ecological Crisis, carbonate platform to backshore environments with hiatus between 9.5 and ∼8.0 Ma representing an extreme lowstand. 5. Maeotian (incomplete 7.65–7.0 Ma): Transgression at 7.65 Ma, followed by a delayed invasion of Maeotian faunas at 7.5 Ma, linked to the reconnection of the Caspian Basin with the rest of the Eastern Paratethys. The well-dated biotic record of Karagiye enhances understanding of Paratethyan hydrological and ecological events in the Caspian Basin and provides a foundation for further palaeoclimatic and palaeobiogeographic studies across Eurasia.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107288"},"PeriodicalIF":3.7,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147886","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}
Pub Date : 2025-01-09DOI: 10.1016/j.marpetgeo.2025.107285
Jiahao Lv , Quanyou Liu , PengPeng Li , Jiarun Liu , Zheng Zhou
Helium (He), as an irreplaceable and scarce strategic resource, is primarily extracted from natural gas for industrial and economic production. Constraining the distribution and enrichment mechanism of He in natural gas is crucial for the effectiveness of helium resource exploration and development. We report natural gas and noble gas isotopic composition in samples from three production areas in the Hetianhe He-rich gas field, Tarim Basin, northwest China. This study investigates differential enrichment of He in the Hetianhe gas field. The He content in the Hetianhe gas field ranges between 0.27% and 0.42%, with an average value of 0.33%. The He content increases gradually from east to west within the gas field and tends to accumulate in structurally high positions. 3He/4He ratios range from 0.045 to 0.076 Ra (where Ra is atmospheric ratio of 3He/4He), with an average of 0.057 Ra, indicating that the helium is typically of crustal origin. The differential enrichment of helium in the Hetianhe gas field is primarily controlled by temperature and pressure conditions, lateral migration, and preservation conditions. Changes in temperature and pressure, especially differences caused by tectonic uplift, lead to degassing, resulting in relative enrichment of helium in structurally high positions. A gas solubility model was used to quantify the subsurface fluid migration pathways and it suggests that, from the eastern production area to the middle production area and then to the western production area, the natural gas/groundwater volume ratio (Vg/Vw) gradually decreases, corresponding to 1.40, 0.35, 0.16, respectively. The Vg/Vw ratio indicates that helium-rich natural gas has undergone lateral migration from east to west. As the migration distance increases, the content of radiogenic isotopes (e.g., 4He and 40Ar) gradually increases. This suggests that during the migration, the helium-rich natural gas continuously extracts radiogenic isotopes, leading to the differential enrichment of helium. It is noteworthy that, compared to degassing, the extraction process may be the primary enrichment mechanism for helium in the Hetianhe gas field. Additionally, the distribution of east-west gypsum-mudstone cap layers results in differential vertical diffusion of helium, which macroscopically controls the differential enrichment of helium. The migration and accumulation of helium exhibit a certain synergy with hydrocarbon reservoir formation. Ultimately, a five-stage conceptual model has been developed in this study to explain the differential enrichment of helium in the Hetianhe gas field.
{"title":"Distribution and enrichment mechanism of helium in the Hetianhe gas field, Tarim basin, northwest China","authors":"Jiahao Lv , Quanyou Liu , PengPeng Li , Jiarun Liu , Zheng Zhou","doi":"10.1016/j.marpetgeo.2025.107285","DOIUrl":"10.1016/j.marpetgeo.2025.107285","url":null,"abstract":"<div><div>Helium (He), as an irreplaceable and scarce strategic resource, is primarily extracted from natural gas for industrial and economic production. Constraining the distribution and enrichment mechanism of He in natural gas is crucial for the effectiveness of helium resource exploration and development. We report natural gas and noble gas isotopic composition in samples from three production areas in the Hetianhe He-rich gas field, Tarim Basin, northwest China. This study investigates differential enrichment of He in the Hetianhe gas field. The He content in the Hetianhe gas field ranges between 0.27% and 0.42%, with an average value of 0.33%. The He content increases gradually from east to west within the gas field and tends to accumulate in structurally high positions. <sup>3</sup>He/<sup>4</sup>He ratios range from 0.045 to 0.076 Ra (where Ra is atmospheric ratio of <sup>3</sup>He/<sup>4</sup>He), with an average of 0.057 Ra, indicating that the helium is typically of crustal origin. The differential enrichment of helium in the Hetianhe gas field is primarily controlled by temperature and pressure conditions, lateral migration, and preservation conditions. Changes in temperature and pressure, especially differences caused by tectonic uplift, lead to degassing, resulting in relative enrichment of helium in structurally high positions. A gas solubility model was used to quantify the subsurface fluid migration pathways and it suggests that, from the eastern production area to the middle production area and then to the western production area, the natural gas/groundwater volume ratio (V<sub>g</sub>/V<sub>w</sub>) gradually decreases, corresponding to 1.40, 0.35, 0.16, respectively. The V<sub>g</sub>/V<sub>w</sub> ratio indicates that helium-rich natural gas has undergone lateral migration from east to west. As the migration distance increases, the content of radiogenic isotopes (e.g., <sup>4</sup>He and <sup>40</sup>Ar) gradually increases. This suggests that during the migration, the helium-rich natural gas continuously extracts radiogenic isotopes, leading to the differential enrichment of helium. It is noteworthy that, compared to degassing, the extraction process may be the primary enrichment mechanism for helium in the Hetianhe gas field. Additionally, the distribution of east-west gypsum-mudstone cap layers results in differential vertical diffusion of helium, which macroscopically controls the differential enrichment of helium. The migration and accumulation of helium exhibit a certain synergy with hydrocarbon reservoir formation. Ultimately, a five-stage conceptual model has been developed in this study to explain the differential enrichment of helium in the Hetianhe gas field.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107285"},"PeriodicalIF":3.7,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148395","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}
Pub Date : 2025-01-07DOI: 10.1016/j.marpetgeo.2025.107287
Hua Tao , Junping Cui , Jiaopeng Sun , Zhanli Ren , Fanfan Zhao , Shihao Su , Wei Guo , Haoyu Song
The Late Carboniferous to Permian is a crucial time epoch that witnessed multiple-stage icehouse-to-greenhouse transitions and amalgamation of the Pangea supercontinent in geological history. In the North China Block (NCB), a sequence of Late Carboniferous to Permian successions preserves dramatic changes related to these climatic and tectonic shifts. Here, we conducted a comprehensive study of sandstone petrology, mudstone whole-rock geochemistry, and detrital zircon U-Pb geochronology on Late Carboniferous to Permian strata in the Wuqi Oilfield, central Ordos Basin of the western NCB. Mudstone geochemistry and sandstone modal composition data indicate that sediments in the central Ordos Basin were deposited in arc/orogen-related tectonic backgrounds, with sources dominantly from erosion of intermediate-acid rocks. Detrital zircon U-Pb analyses yielded 3 major age populations of 2600–2200 Ma, 2100–1700 Ma, and 470–260 Ma, matching well with a northern Inner Mongolia Continental Arc (IMCA) source instead of a southerly Qinling/Qilian source. Three climate warming events were identified by increased levels of continental weathering. The τNa, CIA, and Ln (Al2O3/Na2O) values manifest two positive increasing events and, by reference, climate warming events, represented by high chemical weathering intensity (e.g., CIA >90 and τNa < −0.96), at ca. 302–298 Ma and ca. 292–290 Ma. The first event coincided with the deglaciation event of Gondwana triggered by the Skagerrak-Centered Large Igneous Provinces (LIPs). The second event was associated with the ca. 290 Ma large-scale glacial retreat in Gondwana that was synchronous with the Tarim LIP, Panjal LIP. The zircon Eu/Eu∗ empirical equation data indicates that the crustal thickness of the IMCA thickened from 40-43 km–50 km between approximately 320 Ma and 285 Ma. The increasing relief of the IMCA was recorded by ca. 280–260 Ma craton-wide sedimentary hiatus in the NCB interior. Subsequently, the high relief of the IMCA led to orographic rain shadow and aridification, which caused the third climate warming event, as indicated by the change in mudstone color from black to red.
{"title":"Late Carboniferous to Permian paleoclimatic and tectono-sedimentary evolution of the central Ordos Basin, western north China Block","authors":"Hua Tao , Junping Cui , Jiaopeng Sun , Zhanli Ren , Fanfan Zhao , Shihao Su , Wei Guo , Haoyu Song","doi":"10.1016/j.marpetgeo.2025.107287","DOIUrl":"10.1016/j.marpetgeo.2025.107287","url":null,"abstract":"<div><div>The Late Carboniferous to Permian is a crucial time epoch that witnessed multiple-stage icehouse-to-greenhouse transitions and amalgamation of the Pangea supercontinent in geological history. In the North China Block (NCB), a sequence of Late Carboniferous to Permian successions preserves dramatic changes related to these climatic and tectonic shifts. Here, we conducted a comprehensive study of sandstone petrology, mudstone whole-rock geochemistry, and detrital zircon U-Pb geochronology on Late Carboniferous to Permian strata in the Wuqi Oilfield, central Ordos Basin of the western NCB. Mudstone geochemistry and sandstone modal composition data indicate that sediments in the central Ordos Basin were deposited in arc/orogen-related tectonic backgrounds, with sources dominantly from erosion of intermediate-acid rocks. Detrital zircon U-Pb analyses yielded 3 major age populations of 2600–2200 Ma, 2100–1700 Ma, and 470–260 Ma, matching well with a northern Inner Mongolia Continental Arc (IMCA) source instead of a southerly Qinling/Qilian source. Three climate warming events were identified by increased levels of continental weathering. The τNa, CIA, and Ln (Al<sub>2</sub>O<sub>3</sub>/Na<sub>2</sub>O) values manifest two positive increasing events and, by reference, climate warming events, represented by high chemical weathering intensity (e.g., CIA >90 and τNa < −0.96), at ca. 302–298 Ma and ca. 292–290 Ma. The first event coincided with the deglaciation event of Gondwana triggered by the Skagerrak-Centered Large Igneous Provinces (LIPs). The second event was associated with the ca. 290 Ma large-scale glacial retreat in Gondwana that was synchronous with the Tarim LIP, Panjal LIP. The zircon Eu/Eu∗ empirical equation data indicates that the crustal thickness of the IMCA thickened from 40-43 km–50 km between approximately 320 Ma and 285 Ma. The increasing relief of the IMCA was recorded by ca. 280–260 Ma craton-wide sedimentary hiatus in the NCB interior. Subsequently, the high relief of the IMCA led to orographic rain shadow and aridification, which caused the third climate warming event, as indicated by the change in mudstone color from black to red.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107287"},"PeriodicalIF":3.7,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148393","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}
Pub Date : 2025-01-07DOI: 10.1016/j.marpetgeo.2025.107286
Tong Jia , Liqiang Zhang , Yiming Yan , Ronghu Zhang , Qinglu Zeng , Peng Liu , Junda Hu , Bin Yang
The compaction and grain crushing (GC) of deep-buried sandstone reservoirs play a crucial role in the evolution of reservoir quality. Significant differences exist in the compaction behavior and pore preservation of reservoirs with varying sedimentary grain size characteristics. However, there is a lack of quantitative assessments and mechanistic studies of these processes. This study utilizes the Discrete Element Method (DEM) to simulate two groups of samples with different grain size distributions (GSD) to explore the processes of compaction and pore preservation. Group A samples exhibit a unimodal Gaussian GSD, with the median grain size (Md) gradually increasing, while Group B samples share the same Md but differ in GSD type. The results indicate that with increasing stress, the samples undergo three compaction stages: grain rearrangement (S1), intense GC and rearrangement (S2), and weak GC and rearrangement (S3). In S1, grains rearrange with minimal sliding and no GC, resulting in a low porosity loss rate (Δϕ/Δσ). In S2, GC intensifies, with fragments sliding and filling the pores between grains, leading to a significant increase in Δϕ/Δσ. In S3, a high coordination number reduces GC, and small pores restrict the movement of fragments, resulting in a decrease in Δϕ/Δσ. Md has no effect on Δϕ/Δσ in S1. However, samples with smaller Md experience weaker GC and have smaller pore size, making it more difficult for fragments to fill the pores during S2. In S3, samples with larger Md have higher coordination numbers, providing stronger buffering against GC and resulting in lower Δϕ/Δσ. Additionally, GSD does not affect Δϕ/Δσ during S1. In S2, sample with a coarse-skewed bimodal Gaussian GSD exhibited the weaker GC, smaller difference between pore size and fragment size, resulting in a relatively low Δϕ/Δσ. Therefore, under deep burial conditions, sandstone with small grain size and coarse-skewed bimodal GSD demonstrates strong resistance to compaction and effective pore preservation.
{"title":"Compaction and pore preservation mechanisms of deep-buried sandstone reservoirs under the influence of sedimentary grain size characteristics: Insights from DEM simulations","authors":"Tong Jia , Liqiang Zhang , Yiming Yan , Ronghu Zhang , Qinglu Zeng , Peng Liu , Junda Hu , Bin Yang","doi":"10.1016/j.marpetgeo.2025.107286","DOIUrl":"10.1016/j.marpetgeo.2025.107286","url":null,"abstract":"<div><div>The compaction and grain crushing (GC) of deep-buried sandstone reservoirs play a crucial role in the evolution of reservoir quality. Significant differences exist in the compaction behavior and pore preservation of reservoirs with varying sedimentary grain size characteristics. However, there is a lack of quantitative assessments and mechanistic studies of these processes. This study utilizes the Discrete Element Method (DEM) to simulate two groups of samples with different grain size distributions (GSD) to explore the processes of compaction and pore preservation. Group A samples exhibit a unimodal Gaussian GSD, with the median grain size (<em>M</em><sub><em>d</em></sub>) gradually increasing, while Group B samples share the same <em>M</em><sub><em>d</em></sub> but differ in GSD type. The results indicate that with increasing stress, the samples undergo three compaction stages: grain rearrangement (S1), intense GC and rearrangement (S2), and weak GC and rearrangement (S3). In S1, grains rearrange with minimal sliding and no GC, resulting in a low porosity loss rate (Δ<em>ϕ</em>/Δ<em>σ</em>). In S2, GC intensifies, with fragments sliding and filling the pores between grains, leading to a significant increase in Δ<em>ϕ</em>/Δ<em>σ</em>. In S3, a high coordination number reduces GC, and small pores restrict the movement of fragments, resulting in a decrease in Δ<em>ϕ</em>/Δ<em>σ</em>. <em>M</em><sub><em>d</em></sub> has no effect on Δ<em>ϕ</em>/Δ<em>σ</em> in S1. However, samples with smaller <em>M</em><sub><em>d</em></sub> experience weaker GC and have smaller pore size, making it more difficult for fragments to fill the pores during S2. In S3, samples with larger <em>M</em><sub><em>d</em></sub> have higher coordination numbers, providing stronger buffering against GC and resulting in lower Δ<em>ϕ</em>/Δ<em>σ</em>. Additionally, GSD does not affect Δ<em>ϕ</em>/Δ<em>σ</em> during S1. In S2, sample with a coarse-skewed bimodal Gaussian GSD exhibited the weaker GC, smaller difference between pore size and fragment size, resulting in a relatively low Δ<em>ϕ</em>/Δ<em>σ</em>. Therefore, under deep burial conditions, sandstone with small grain size and coarse-skewed bimodal GSD demonstrates strong resistance to compaction and effective pore preservation.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107286"},"PeriodicalIF":3.7,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148745","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}
Pub Date : 2025-01-07DOI: 10.1016/j.marpetgeo.2025.107289
Fei Lin , Jian Wang , Ahmed Mansour , Xiugen Fu , Shaohua Su , Ying Nie , Mohamed S. Ahmed , Shengqiang Zeng , Xueren Li
The Carnian Pluvial Episode (CPE; ∼233 Ma) is marked by global warming associated with an intensified hydrological cycle and increased siliciclastic input, coinciding with a widespread crisis in carbonate production. It was further linked to the eruption of the Wrangellia Large Igneous Province (W-LIP), seawater hypoxia, and significant biotic turnover. While some studies have investigated the CPE in Tibet, the environmental and oceanographic processes leading up to this event have received limited attention. In this study, total organic carbon (TOC), biomarker, inorganic geochemistry, and pyrite framboid petrography of samples collected from the Upper Triassic (Carnian) Bagong Formation in the QZ8 well of the Qiangtang Basin (Tibet) were performed to explore the environmental, paleoceanographic, and organic matter controlling processes preceding the CPE. Results exhibit moderate to high enrichments of trace element redox proxies, such as U, Mo, and V, suggesting that the Bagong Formation was deposited under deoxygenation conditions, from severe anoxia to intermittent euxinia prior to the CPE. The presence of pyrite framboids with small mean diameters and narrow distribution ranges further support this interpretation of deficient redox conditions in bottom and pore waters. Additionally, the moderate to strong positive correlations between enrichment factor values of Mo and V and TOC content indicate that the available organic matter was controlled by oxygen-depleted conditions. Enrichment of Cu, Cd, and Zn, along with their Al-normalized ratios that show strong positive correlations with TOC content, reveal high marine primary productivity before the CPE. Meanwhile, the Si/Al, Ti/Al, and Zr/Al ratios showed cyclic patterns around moderate values, suggesting a modest terrigenous sediment supply, consistent with high Sr/Ba and Sr/Al ratios indicating a predominantly saline environment interspersed with enhanced terrestrial/riverine runoff during deposition. Biomarker analysis reveals a substantial contribution of tricyclic and tetracyclic terpanes, with the C19/C23 TT and C20/C23 TT ratios indicating increased terrestrial organic matter input, supported by the presence of Type III kerogen in the Bagong Formation. Prior to the CPE, the climate was warm and humid, leading to accelerated hydrological cycling and freshwater influx of terrestrial organic matter into the Qiangtang Basin. This likely triggered an increase in nutrient supply under severe deoxygenation conditions and a high sedimentation rate, resulting in enhanced organic matter production and preservation regimes while minimizing the carbonate dilution effect.
{"title":"Deoxygenation preceding the Carnian Pluvial Episode (Late Triassic) in the Qiangtang Basin (Tibetan Plateau): Implications for organic and inorganic geochemistry and petrography","authors":"Fei Lin , Jian Wang , Ahmed Mansour , Xiugen Fu , Shaohua Su , Ying Nie , Mohamed S. Ahmed , Shengqiang Zeng , Xueren Li","doi":"10.1016/j.marpetgeo.2025.107289","DOIUrl":"10.1016/j.marpetgeo.2025.107289","url":null,"abstract":"<div><div>The Carnian Pluvial Episode (CPE; ∼233 Ma) is marked by global warming associated with an intensified hydrological cycle and increased siliciclastic input, coinciding with a widespread crisis in carbonate production. It was further linked to the eruption of the Wrangellia Large Igneous Province (W-LIP), seawater hypoxia, and significant biotic turnover. While some studies have investigated the CPE in Tibet, the environmental and oceanographic processes leading up to this event have received limited attention. In this study, total organic carbon (TOC), biomarker, inorganic geochemistry, and pyrite framboid petrography of samples collected from the Upper Triassic (Carnian) Bagong Formation in the QZ8 well of the Qiangtang Basin (Tibet) were performed to explore the environmental, paleoceanographic, and organic matter controlling processes preceding the CPE. Results exhibit moderate to high enrichments of trace element redox proxies, such as U, Mo, and V, suggesting that the Bagong Formation was deposited under deoxygenation conditions, from severe anoxia to intermittent euxinia prior to the CPE. The presence of pyrite framboids with small mean diameters and narrow distribution ranges further support this interpretation of deficient redox conditions in bottom and pore waters. Additionally, the moderate to strong positive correlations between enrichment factor values of Mo and V and TOC content indicate that the available organic matter was controlled by oxygen-depleted conditions. Enrichment of Cu, Cd, and Zn, along with their Al-normalized ratios that show strong positive correlations with TOC content, reveal high marine primary productivity before the CPE. Meanwhile, the Si/Al, Ti/Al, and Zr/Al ratios showed cyclic patterns around moderate values, suggesting a modest terrigenous sediment supply, consistent with high Sr/Ba and Sr/Al ratios indicating a predominantly saline environment interspersed with enhanced terrestrial/riverine runoff during deposition. Biomarker analysis reveals a substantial contribution of tricyclic and tetracyclic terpanes, with the C<sub>19</sub>/C<sub>23</sub> TT and C<sub>20</sub>/C<sub>23</sub> TT ratios indicating increased terrestrial organic matter input, supported by the presence of Type III kerogen in the Bagong Formation. Prior to the CPE, the climate was warm and humid, leading to accelerated hydrological cycling and freshwater influx of terrestrial organic matter into the Qiangtang Basin. This likely triggered an increase in nutrient supply under severe deoxygenation conditions and a high sedimentation rate, resulting in enhanced organic matter production and preservation regimes while minimizing the carbonate dilution effect.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107289"},"PeriodicalIF":3.7,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148746","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}
Pub Date : 2025-01-04DOI: 10.1016/j.marpetgeo.2025.107284
Yuyue Huang , Guiwen Wang , Lichun Kuang , Chaoliu Li , Ming Wang , Song Wang , Hongbin Li , Fei Zhao , Jin Lai
Fine-grained sedimentary rocks have been widely regarded as effective reservoirs and source rocks of tight oil and shale oil. Natural fractures play a critical role in promoting oil enrichment and enhancing production. Clarifying the contribution of fractures to reservoir quality is important but lacks systematic research. Limitations exist in both core outcrop descriptions and seismic predictions of fractures. New technological advancements in well logs offer new avenues for multi-scale fracture characterization. Image logs and array acoustic logs are used to systematically investigate natural fractures in the Member 7 of Upper Triassic Yanchang Formation (Chang 7) shale oil reservoirs in the Ordos Basin. Natural fractures include tectonic fractures and bedding-parallel fractures. An absolute match between core data and image log data is achieved through the precise core homing. The reliability of image logs is enhanced by establishing the fracture identification templates under the core scale. The Vp/Vs ratio, energy attenuation, waveform distortion, and S-wave slowness anisotropy of array acoustic logs are effective for detecting and predicting natural fractures around the borehole. The impact of natural fractures on reservoir quality is evaluated by considering fracture parameters, radial extension and their relationship with in-situ stress. The results show that combining the occurrence and type of fractures detected by image logs and the fracture extension state indicated by fast and slow S-wave radial variations, the effectiveness of fractures around the wellbore can be accurately evaluated. T1-T2 maps from 2D NMR logs also offer insights into the relationship between fractures and reservoir quality. Natural fractures that are nearly parallel to the direction of the in-situ SHmax have proven to be effective and significantly enhance hydrocarbon productivity. The research above may aid in optimizing sweet spot evaluation and stimulating shale oil production.
{"title":"Recognition and impact on reservoir quality of fractures in fine-grained sedimentary rocks using image and array acoustic logs","authors":"Yuyue Huang , Guiwen Wang , Lichun Kuang , Chaoliu Li , Ming Wang , Song Wang , Hongbin Li , Fei Zhao , Jin Lai","doi":"10.1016/j.marpetgeo.2025.107284","DOIUrl":"10.1016/j.marpetgeo.2025.107284","url":null,"abstract":"<div><div>Fine-grained sedimentary rocks have been widely regarded as effective reservoirs and source rocks of tight oil and shale oil. Natural fractures play a critical role in promoting oil enrichment and enhancing production. Clarifying the contribution of fractures to reservoir quality is important but lacks systematic research. Limitations exist in both core outcrop descriptions and seismic predictions of fractures. New technological advancements in well logs offer new avenues for multi-scale fracture characterization. Image logs and array acoustic logs are used to systematically investigate natural fractures in the Member 7 of Upper Triassic Yanchang Formation (Chang 7) shale oil reservoirs in the Ordos Basin. Natural fractures include tectonic fractures and bedding-parallel fractures. An absolute match between core data and image log data is achieved through the precise core homing. The reliability of image logs is enhanced by establishing the fracture identification templates under the core scale. The Vp/Vs ratio, energy attenuation, waveform distortion, and S-wave slowness anisotropy of array acoustic logs are effective for detecting and predicting natural fractures around the borehole. The impact of natural fractures on reservoir quality is evaluated by considering fracture parameters, radial extension and their relationship with in-situ stress. The results show that combining the occurrence and type of fractures detected by image logs and the fracture extension state indicated by fast and slow S-wave radial variations, the effectiveness of fractures around the wellbore can be accurately evaluated. T<sub>1</sub>-T<sub>2</sub> maps from 2D NMR logs also offer insights into the relationship between fractures and reservoir quality. Natural fractures that are nearly parallel to the direction of the in-situ SH<sub>max</sub> have proven to be effective and significantly enhance hydrocarbon productivity. The research above may aid in optimizing sweet spot evaluation and stimulating shale oil production.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107284"},"PeriodicalIF":3.7,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147829","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}
The Oligo-Miocene Asmari Formation in the Shadegan Oil Field, located in the Dezful Embayment in southwestern Iran, is renowned for its complex geological characteristics in the Middle East. This study systematically investigates the drivers of reservoir quality, emphasizing the interplay between geological settings, depositional environments and facies, diagenetic processes, and tectonic activities that shape porosity and permeability. Based on the sedimentary architecture and analysis of the facies associations this formation contains a diverse assemblage of carbonate and siliciclastic lithofacies (twenty-six carbonate microfacies and six siliciclastic facies association), revealing a mixed depositional system influenced by siliciclastic influx, climatic and sea-level fluctuations, and tectonic movements. Extensive core and petrophysical data analysis were utilized to identify hydraulic flow units (HFUs) and optimize reservoir zonation using advanced analytical techniques, including machine learning algorithms. Four hydraulic flow units (HFUs) were determined and evaluated against lithology and petrophysical values: baffle unit (HFU1), normal unit (HFU2), permeable unit (HFU3), and high permeable unit (HFU4).
Key findings underscore the critical role of fractures in enhancing reservoir productivity, significantly impacting hydrocarbon recovery rates. Additionally, the analysis of diagenetic processes such as dolomitization, cementation, and dissolution reveals their dual impact—either enhancing or degrading reservoir quality. The study concludes that effective reservoir characterization depends on integrated methodologies, which combine traditional geological assessments with modern data processing techniques. This approach enhances exploration and production strategies in complex carbonate reservoirs. Ultimately, this research offers new insights into a comprehensive framework for understanding the drivers of reservoir quality in the Asmari Formation and their implications for hydrocarbon development.
{"title":"Reservoir quality drivers in the Oligo-Miocene Asmari Formation, Dezful Embayment, Iran: Facies, diagenesis, and tectonic controls","authors":"Roghayeh Fallah-Bagtash , Aram Bayet-Goll , Armin Omidpour , Umid Kakemem","doi":"10.1016/j.marpetgeo.2024.107279","DOIUrl":"10.1016/j.marpetgeo.2024.107279","url":null,"abstract":"<div><div>The Oligo-Miocene Asmari Formation in the Shadegan Oil Field, located in the Dezful Embayment in southwestern Iran, is renowned for its complex geological characteristics in the Middle East. This study systematically investigates the drivers of reservoir quality, emphasizing the interplay between geological settings, depositional environments and facies, diagenetic processes, and tectonic activities that shape porosity and permeability. Based on the sedimentary architecture and analysis of the facies associations this formation contains a diverse assemblage of carbonate and siliciclastic lithofacies (twenty-six carbonate microfacies and six siliciclastic facies association), revealing a mixed depositional system influenced by siliciclastic influx, climatic and sea-level fluctuations, and tectonic movements. Extensive core and petrophysical data analysis were utilized to identify hydraulic flow units (HFUs) and optimize reservoir zonation using advanced analytical techniques, including machine learning algorithms. Four hydraulic flow units (HFUs) were determined and evaluated against lithology and petrophysical values: baffle unit (HFU1), normal unit (HFU2), permeable unit (HFU3), and high permeable unit (HFU4).</div><div>Key findings underscore the critical role of fractures in enhancing reservoir productivity, significantly impacting hydrocarbon recovery rates. Additionally, the analysis of diagenetic processes such as dolomitization, cementation, and dissolution reveals their dual impact—either enhancing or degrading reservoir quality. The study concludes that effective reservoir characterization depends on integrated methodologies, which combine traditional geological assessments with modern data processing techniques. This approach enhances exploration and production strategies in complex carbonate reservoirs. Ultimately, this research offers new insights into a comprehensive framework for understanding the drivers of reservoir quality in the Asmari Formation and their implications for hydrocarbon development.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107279"},"PeriodicalIF":3.7,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148744","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}
Pub Date : 2025-01-04DOI: 10.1016/j.marpetgeo.2024.107282
Omid Falahatkhah , Abbas Ghaderi , Ali Kadkhodaie , Reza Rezaee
This study investigates the terrigenous sediment influx in the Canning Basin, Western Australia, during the Darriwilian Stage of the Middle Ordovician, specifically correlating it with Milankovitch obliquity cycles. The basic stratigraphic data came from the Goldwyer Formation within Theia 1 well which was dated using the U-Pb zircon geochronology. Four ash beds, located in the lower part of the formation, yielded distinct radiometric ages at depths of 1550.81 m (466.07 ± 0.12 Ma), 1559.81 m (466.31 ± 0.11 Ma), 1572.55 m (466.84 ± 0.11 Ma), and 1587.10 m (467.12 ± 0.14 Ma) which following the age of conodont biostratigraphy. Based on the astrochronological analysis, duration of the Darriwilian in the Canning Basin is estimated at 9.03 ± 0.3 Myr, providing a precise chronological framework for the studied sedimentary successions. Core sample examinations indicated notable lithological discrepancies with a pronounced increase in terrigenous sedimentation recorded during intervals of elevated obliquity. Quantitative analysis revealed that sedimentation rates reached their zenith in correlation with ∼1.2 Myr obliquity cycles, resulting in substantial accumulations of fine-grained sediments, notably shale and mudstone. Petrographic examination identified a predominance of silt and clay-sized particles during these high influx periods, confirming a direct relationship between obliquity and sediment composition and led to enhanced fossil preservation. ICP-MS analysis of 39 samples indicated variations in elemental abundance that corresponded with the identified obliquity cycles, further supporting the correlation between climate changes and sediment influx. Scatter diagrams illustrated the relationships between various geochemical proxies, revealing trends that align with the sedimentary data. The findings confirm that the Canning Basin experienced significant shifts in sedimentation patterns driven by obliquity-induced climate changes during the Middle Ordovician. This research demonstrates how obliquity affects sedimentation rates and fossil preservation in the Canning Basin, enhancing our understanding of its geological history.
{"title":"Milankovitch-driven terrigenous deposit influx in Middle Ordovician marine successions of Western Australia: Insights for paleoclimate and geochronology","authors":"Omid Falahatkhah , Abbas Ghaderi , Ali Kadkhodaie , Reza Rezaee","doi":"10.1016/j.marpetgeo.2024.107282","DOIUrl":"10.1016/j.marpetgeo.2024.107282","url":null,"abstract":"<div><div>This study investigates the terrigenous sediment influx in the Canning Basin, Western Australia, during the Darriwilian Stage of the Middle Ordovician, specifically correlating it with Milankovitch obliquity cycles. The basic stratigraphic data came from the Goldwyer Formation within Theia 1 well which was dated using the U-Pb zircon geochronology. Four ash beds, located in the lower part of the formation, yielded distinct radiometric ages at depths of 1550.81 m (466.07 ± 0.12 Ma), 1559.81 m (466.31 ± 0.11 Ma), 1572.55 m (466.84 ± 0.11 Ma), and 1587.10 m (467.12 ± 0.14 Ma) which following the age of conodont biostratigraphy. Based on the astrochronological analysis, duration of the Darriwilian in the Canning Basin is estimated at 9.03 ± 0.3 Myr, providing a precise chronological framework for the studied sedimentary successions. Core sample examinations indicated notable lithological discrepancies with a pronounced increase in terrigenous sedimentation recorded during intervals of elevated obliquity. Quantitative analysis revealed that sedimentation rates reached their zenith in correlation with ∼1.2 Myr obliquity cycles, resulting in substantial accumulations of fine-grained sediments, notably shale and mudstone. Petrographic examination identified a predominance of silt and clay-sized particles during these high influx periods, confirming a direct relationship between obliquity and sediment composition and led to enhanced fossil preservation. ICP-MS analysis of 39 samples indicated variations in elemental abundance that corresponded with the identified obliquity cycles, further supporting the correlation between climate changes and sediment influx. Scatter diagrams illustrated the relationships between various geochemical proxies, revealing trends that align with the sedimentary data. The findings confirm that the Canning Basin experienced significant shifts in sedimentation patterns driven by obliquity-induced climate changes during the Middle Ordovician. This research demonstrates how obliquity affects sedimentation rates and fossil preservation in the Canning Basin, enhancing our understanding of its geological history.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"173 ","pages":"Article 107282"},"PeriodicalIF":3.7,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147884","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}
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