Pub Date : 2025-09-04DOI: 10.1016/j.sedgeo.2025.106961
Zhibo Yang , Hancheng Ji , Yanqing Shi , Ting Liang , Zhidong Bao
<div><div>The late Ediacaran ocean witnessed a critical phase in the evolution of early life, during which redox conditions were closely linked to biological innovation. Nevertheless, the nature of these redox conditions and their interactions with evolving ecosystems remain debated. This study provides a systematic investigation of the petrographic and geochemical characteristics of microbial dolostones from the Dengying Formation on the Yangtze Platform, South China. The results reveal that microbial dolomites in this unit comprise a diverse suite of lithofacies—bioclastic, stromatolitic, oncoidal, foam-spongy, and thrombolitic dolomites—indicative of intertidal to subtidal depositional settings. Microbialite components are classified into microbial matrix, fibrous dolomite cements, and clear equant dolomite cements. Among these, Fibrous dolomite is particularly well-developed, and its cathodoluminescence zoning and length-slow optical properties suggest <em>syn</em>-depositional precipitation during early diagenesis. Combined δ<sup>13</sup>C and <sup>87</sup>Sr/<sup>86</sup>Sr data suggest a warm and humid climate with high primary productivity and intense continental weathering during the Z<sub>2</sub>dn<sup>2</sup> interval, followed by a decline in sedimentation rates during Z<sub>2</sub>dn<sup>4</sup>, albeit with continued robust carbonate deposition. All dolomite components exhibit distinct negative cerium anomalies (Ce/Ce* < 1), heavy rare earth elements (HREEs) enrichment, and elevated Y/Ho ratios, collectively indicating deposition under well‑oxygenated shallow marine conditions. Notably, the fibrous dolomite component displays the most pronounced oxidative signature, with oxygen levels at the sediment–water interface potentially approaching atmospheric values. In contrast, the clear equant dolomite cements components reflect suboxic to weakly oxic conditions, suggesting a stratified redox water column during the late Ediacaran. These observations imply that localized oxygen-rich zones on the seafloor may have developed through microbial oxygen production. When compared across the entire Ediacaran, the widespread microbial dolomites of the Dengying Formation and their associated oxic conditions likely provided key ecological niches for early benthic metazoans, such as bilaterians. The oxygenation process recorded in this formation may have played an important role in setting the stage for the Cambrian Explosion. The Dengying Formation thus captures a significant shallow-marine oxygenation event closely associated with algal proliferation and the emergence of multicellular life, underscoring the role of biologically mediated environmental feedbacks during the terminal Neoproterozoic. This study enhances our understanding of the interplay between seawater redox structure and microbial activity at the close of the Ediacaran, and supports the interpretation that microbial metabolism may have been a key regulatory mechanism in the devel
{"title":"Redox stratification and ecological implications of microbial dolomites in the late Ediacaran Dengying Formation, Yangtze platform","authors":"Zhibo Yang , Hancheng Ji , Yanqing Shi , Ting Liang , Zhidong Bao","doi":"10.1016/j.sedgeo.2025.106961","DOIUrl":"10.1016/j.sedgeo.2025.106961","url":null,"abstract":"<div><div>The late Ediacaran ocean witnessed a critical phase in the evolution of early life, during which redox conditions were closely linked to biological innovation. Nevertheless, the nature of these redox conditions and their interactions with evolving ecosystems remain debated. This study provides a systematic investigation of the petrographic and geochemical characteristics of microbial dolostones from the Dengying Formation on the Yangtze Platform, South China. The results reveal that microbial dolomites in this unit comprise a diverse suite of lithofacies—bioclastic, stromatolitic, oncoidal, foam-spongy, and thrombolitic dolomites—indicative of intertidal to subtidal depositional settings. Microbialite components are classified into microbial matrix, fibrous dolomite cements, and clear equant dolomite cements. Among these, Fibrous dolomite is particularly well-developed, and its cathodoluminescence zoning and length-slow optical properties suggest <em>syn</em>-depositional precipitation during early diagenesis. Combined δ<sup>13</sup>C and <sup>87</sup>Sr/<sup>86</sup>Sr data suggest a warm and humid climate with high primary productivity and intense continental weathering during the Z<sub>2</sub>dn<sup>2</sup> interval, followed by a decline in sedimentation rates during Z<sub>2</sub>dn<sup>4</sup>, albeit with continued robust carbonate deposition. All dolomite components exhibit distinct negative cerium anomalies (Ce/Ce* < 1), heavy rare earth elements (HREEs) enrichment, and elevated Y/Ho ratios, collectively indicating deposition under well‑oxygenated shallow marine conditions. Notably, the fibrous dolomite component displays the most pronounced oxidative signature, with oxygen levels at the sediment–water interface potentially approaching atmospheric values. In contrast, the clear equant dolomite cements components reflect suboxic to weakly oxic conditions, suggesting a stratified redox water column during the late Ediacaran. These observations imply that localized oxygen-rich zones on the seafloor may have developed through microbial oxygen production. When compared across the entire Ediacaran, the widespread microbial dolomites of the Dengying Formation and their associated oxic conditions likely provided key ecological niches for early benthic metazoans, such as bilaterians. The oxygenation process recorded in this formation may have played an important role in setting the stage for the Cambrian Explosion. The Dengying Formation thus captures a significant shallow-marine oxygenation event closely associated with algal proliferation and the emergence of multicellular life, underscoring the role of biologically mediated environmental feedbacks during the terminal Neoproterozoic. This study enhances our understanding of the interplay between seawater redox structure and microbial activity at the close of the Ediacaran, and supports the interpretation that microbial metabolism may have been a key regulatory mechanism in the devel","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"489 ","pages":"Article 106961"},"PeriodicalIF":2.9,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145057215","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 : 2025-09-03DOI: 10.1016/j.sedgeo.2025.106959
J. Javier Álvaro , Aram Bayet-Goll , Mehdi Daraei , Blanca Martínez-Benítez
The Alborz Mountains in northern Iran represent one of the few exceptions to the worldwide decline in Miaolingian–Furongian (Cambrian) carbonate abundance and reefal volume, likely related to the arrival of northeastern Gondwana to subtropical latitudes. This Gondwana margin recorded the stepwise nucleation of microbial and shelly carbonate factories, lithostratigraphically recognized as members of the Lalun and Mila formations. The late Cambrian Epoch 2 to Miaolingian interval displays the development of oncoid-pisoid accumulations and microbial build-ups, with laminated and clotted textures, in open-sea and protected (back-barrier) settings. In contrast, the late Miaolingian and Furongian interval recorded a generalized establishment of pelmatozoan-rhynchonelliformean meadows, locally affected by horst-and-graben topographies. Hanging-wall blocks offered some protection from high-energy, shallow-water conditions, which favoured the growth of anthaspidellid-microbial reef complexes. The primary porosity recorded in the pelmatozoan-rhynchonelliformean shell beds, and the associated microboring and micritization of skeletal walls, favoured the episodic development of carbonate and iron oxyhydroxide hardgrounds. Such a singularity leads to the development of a more comprehensive global model linked to Miaolingian–Furongian progressive declines in 87Sr/86Sr ratios, estimated extent of carbonate platforms and reefal volume and atmospheric O2 (punctuated by a sharp increase related to the SPICE event), coeval with relative increases in seawater calcite saturation. In some subtropical areas, such as in the Alborz margin of Gondwana, the re-occurrence of metazoan frame-builders took place in late Miaolingian times, and their subsequent reefal success was primarily controlled by tectonic activity and the nucleation of hardgrounds in highly porous pelmatozoan-rhynchonelliformean shell beds.
{"title":"Cambrian reef complexes and pelmatozoan-rhynchonelliformean meadows from the Alborz Mountains, northern Iran: A reassessment of the Miaolingian–Furongian paucity of metazoan reefs paradigm","authors":"J. Javier Álvaro , Aram Bayet-Goll , Mehdi Daraei , Blanca Martínez-Benítez","doi":"10.1016/j.sedgeo.2025.106959","DOIUrl":"10.1016/j.sedgeo.2025.106959","url":null,"abstract":"<div><div>The Alborz Mountains in northern Iran represent one of the few exceptions to the worldwide decline in Miaolingian–Furongian (Cambrian) carbonate abundance and reefal volume, likely related to the arrival of northeastern Gondwana to subtropical latitudes. This Gondwana margin recorded the stepwise nucleation of microbial and shelly carbonate factories, lithostratigraphically recognized as members of the Lalun and Mila formations. The late Cambrian Epoch 2 to Miaolingian interval displays the development of oncoid-pisoid accumulations and microbial build-ups, with laminated and clotted textures, in open-sea and protected (back-barrier) settings. In contrast, the late Miaolingian and Furongian interval recorded a generalized establishment of pelmatozoan-rhynchonelliformean meadows, locally affected by horst-and-graben topographies. Hanging-wall blocks offered some protection from high-energy, shallow-water conditions, which favoured the growth of anthaspidellid-microbial reef complexes. The primary porosity recorded in the pelmatozoan-rhynchonelliformean shell beds, and the associated microboring and micritization of skeletal walls, favoured the episodic development of carbonate and iron oxyhydroxide hardgrounds. Such a singularity leads to the development of a more comprehensive global model linked to Miaolingian–Furongian progressive declines in <sup>87</sup>Sr/<sup>86</sup>Sr ratios, estimated extent of carbonate platforms and reefal volume and atmospheric O<sub>2</sub> (punctuated by a sharp increase related to the SPICE event), coeval with relative increases in seawater calcite saturation. In some subtropical areas, such as in the Alborz margin of Gondwana, the re-occurrence of metazoan frame-builders took place in late Miaolingian times, and their subsequent reefal success was primarily controlled by tectonic activity and the nucleation of hardgrounds in highly porous pelmatozoan-rhynchonelliformean shell beds.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"489 ","pages":"Article 106959"},"PeriodicalIF":2.9,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145057214","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 : 2025-09-02DOI: 10.1016/j.sedgeo.2025.106958
Zixiao Peng , Jianhua Qu , En Xie , Chunqiang Chen , Bang Zeng , Dancheng Zhu , Ke Zhang , Yuyuan Li , He Wang
Depositional processes recorded by coastal deposits may vary rapidly during transgression due to the interactions of wave, river, and tidal processes, leading to the diversity of facies models. Reconstructing a reliable, detailed facies model associated with depositional processes remains challenging unless ichnological features are considered. Integrated sedimentological and ichnological analyses of high-resolution core samples, wireline log, and seismic data from the Lower Cretaceous Zubair Formation, central Mesopotamian Basin, are undertaken to propose a tide-dominated model within transgressive succession. The presence of sporadic river-influenced sedimentary structures, variability in ichnodiversity and bioturbation intensity, and abundant tidal physical indicators attest to the strong influence of tide-generated currents during deposition. In a transgressive upward-fining succession, seven facies associations are identified based on differences in sedimentological and ichnological indicators, and further grouped into two environments (tide-dominated estuary and open coast tidal flat), which are both considered as first-order tidal coastal environments. Deposits of estuaries are occupied by mixed Cruziana-Skolithos ichnofacies and dominance of channel-bar complexes, while local storm-influenced structures, higher ichnodiversity and bioturbation intensity, and well-expressed Cruziana and Skolithos ichnofacies clearly characterize the open coast. River-dominated paleovalley evolved into the tide-dominated estuary and then transformed into the open coast tidal flat as global sea-level rose, with increasing ichnodiversity, bioturbation intensity, and weakening fluvial influence. For the first time in the region, distinct deposits of estuary and open coast are recognized, indicating the development of facies diversity during long-term transgression. High accommodation, topographic features, limited sediment supply, and sea level rise are responsible for the spatiotemporal differential distribution of these two depositional systems. At the regional scale, tidal environments, river-influenced, and river-dominated deltas were distributed along the coastline from northwest to southeast due to the relatively increasing sediment supply from the Arabian Shield towards the southeast. The results of this study improve our understanding of regional paleogeography in the central Mesopotamian Basin, NE Arabian Plate, during the Barremian, and provide a case for understanding the diversity and sedimentary evolution of tidal facies models, which can be applied to other transgressive sequences in deep-time basins worldwide.
{"title":"Sedimentological and ichnological characterization of tide-dominated succession during transgression in the Lower Cretaceous Zubair Formation, central Mesopotamian Basin","authors":"Zixiao Peng , Jianhua Qu , En Xie , Chunqiang Chen , Bang Zeng , Dancheng Zhu , Ke Zhang , Yuyuan Li , He Wang","doi":"10.1016/j.sedgeo.2025.106958","DOIUrl":"10.1016/j.sedgeo.2025.106958","url":null,"abstract":"<div><div>Depositional processes recorded by coastal deposits may vary rapidly during transgression due to the interactions of wave, river, and tidal processes, leading to the diversity of facies models. Reconstructing a reliable, detailed facies model associated with depositional processes remains challenging unless ichnological features are considered. Integrated sedimentological and ichnological analyses of high-resolution core samples, wireline log, and seismic data from the Lower Cretaceous Zubair Formation, central Mesopotamian Basin, are undertaken to propose a tide-dominated model within transgressive succession. The presence of sporadic river-influenced sedimentary structures, variability in ichnodiversity and bioturbation intensity, and abundant tidal physical indicators attest to the strong influence of tide-generated currents during deposition. In a transgressive upward-fining succession, seven facies associations are identified based on differences in sedimentological and ichnological indicators, and further grouped into two environments (tide-dominated estuary and open coast tidal flat), which are both considered as first-order tidal coastal environments. Deposits of estuaries are occupied by mixed <em>Cruziana-Skolithos</em> ichnofacies and dominance of channel-bar complexes, while local storm-influenced structures, higher ichnodiversity and bioturbation intensity, and well-expressed <em>Cruziana and Skolithos</em> ichnofacies clearly characterize the open coast. River-dominated paleovalley evolved into the tide-dominated estuary and then transformed into the open coast tidal flat as global sea-level rose, with increasing ichnodiversity, bioturbation intensity, and weakening fluvial influence. For the first time in the region, distinct deposits of estuary and open coast are recognized, indicating the development of facies diversity during long-term transgression. High accommodation, topographic features, limited sediment supply, and sea level rise are responsible for the spatiotemporal differential distribution of these two depositional systems. At the regional scale, tidal environments, river-influenced, and river-dominated deltas were distributed along the coastline from northwest to southeast due to the relatively increasing sediment supply from the Arabian Shield towards the southeast. The results of this study improve our understanding of regional paleogeography in the central Mesopotamian Basin, NE Arabian Plate, during the Barremian, and provide a case for understanding the diversity and sedimentary evolution of tidal facies models, which can be applied to other transgressive sequences in deep-time basins worldwide.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"489 ","pages":"Article 106958"},"PeriodicalIF":2.9,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145057183","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 : 2025-09-01DOI: 10.1016/j.sedgeo.2025.106957
Ondřej Bábek , Hedvika Weinerová , Lukáš Ackerman , Daniel Šimíček , Jaroslav Kapusta , Ladislav Strnad
The palaeoclimatic significance of continental red beds (CRB) is the subject of a long-standing debate. The CRBs are strikingly often found in association with arid, aeolian sediments, humid fluvial sediments and palaeosols, reflecting variable climatic regimes. In this study, diffuse reflectance spectroscopy (DRS) is used in combination with facies analysis, petrology, bulk-rock and in-situ major and trace element geochemistry, and molybdenum stable isotopes to better understand the origin and distribution of the hematite pigment in a spectrum of Permo-Triassic aeolian, fluvial and pedogenic facies of the Colorado Plateau, Utah. Their red colour is characterized by high (> 30) percentage of red-band (625–700 nm) reflectance in the DRS spectra and high hematite-to-goethite peak height ratios (1.5 to 5.7) from their first derivatives. Most hematite occurs in form of submicronic to micron-sized, platy crystals in altered biotite grains, clayey grain coatings, clayey matrix, pyrite framboid pseudomorphs, and as pore-filling cement. Hematite is most abundant in palaeosols, but also present in aeolian, sand dune and damp interdune deposits, fluvial channel-fill, sandy and gravelly bars, and floodplain deposits. Iron for the hematitization was supplied from reductive release of Fe2+ from biotite and clay minerals. The hematitization itself occurred under oxic conditions, associated with formation of kaolinite, mobilization of V, Mo, As, U, and fractionation of rare earth elements and Mo isotopes, especially in lateritic palaeosols. Hematitization during weathering, pedogenesis, transportation and early diagenesis, and reworking and redeposition of the red material by rivers and wind is thought to be the principal mechanism of the formation of red beds in the Colorado Plateau. The processes of hematitization and the fluvial-aeolian dynamics were controlled by alternation of wetter and drier periods likely caused by the Permo-Triassic Pangean mega-monsoonal climatic regime.
{"title":"Petrological and geochemical evidence of hematite growth and dispersal in Permo-Triassic red beds under the Pangea mega-monsoon climate, Colorado Plateau, Utah","authors":"Ondřej Bábek , Hedvika Weinerová , Lukáš Ackerman , Daniel Šimíček , Jaroslav Kapusta , Ladislav Strnad","doi":"10.1016/j.sedgeo.2025.106957","DOIUrl":"10.1016/j.sedgeo.2025.106957","url":null,"abstract":"<div><div>The palaeoclimatic significance of continental red beds (CRB) is the subject of a long-standing debate. The CRBs are strikingly often found in association with arid, aeolian sediments, humid fluvial sediments and palaeosols, reflecting variable climatic regimes. In this study, diffuse reflectance spectroscopy (DRS) is used in combination with facies analysis, petrology, bulk-rock and in-situ major and trace element geochemistry, and molybdenum stable isotopes to better understand the origin and distribution of the hematite pigment in a spectrum of Permo-Triassic aeolian, fluvial and pedogenic facies of the Colorado Plateau, Utah. Their red colour is characterized by high (> 30) percentage of red-band (625–700 nm) reflectance in the DRS spectra and high hematite-to-goethite peak height ratios (1.5 to 5.7) from their first derivatives. Most hematite occurs in form of submicronic to micron-sized, platy crystals in altered biotite grains, clayey grain coatings, clayey matrix, pyrite framboid pseudomorphs, and as pore-filling cement. Hematite is most abundant in palaeosols, but also present in aeolian, sand dune and damp interdune deposits, fluvial channel-fill, sandy and gravelly bars, and floodplain deposits. Iron for the hematitization was supplied from reductive release of Fe<sup>2+</sup> from biotite and clay minerals. The hematitization itself occurred under oxic conditions, associated with formation of kaolinite, mobilization of V, Mo, As, U, and fractionation of rare earth elements and Mo isotopes, especially in lateritic palaeosols. Hematitization during weathering, pedogenesis, transportation and early diagenesis, and reworking and redeposition of the red material by rivers and wind is thought to be the principal mechanism of the formation of red beds in the Colorado Plateau. The processes of hematitization and the fluvial-aeolian dynamics were controlled by alternation of wetter and drier periods likely caused by the Permo-Triassic Pangean mega-monsoonal climatic regime.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"489 ","pages":"Article 106957"},"PeriodicalIF":2.9,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145057213","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 : 2025-08-14DOI: 10.1016/j.sedgeo.2025.106948
Haocheng Shi , Benzhong Xian , Yichen Liu , Zhiyun Yu , Lin Zhao , Junyang Geng , Rongheng Tian , Qianran Wu , Li Liu , Yujie Shuai , Yi Shu
Unlike marine sedimentary basins, lacustrine sedimentary basins are more sensitive to small-scale climatic changes (fourth-order and higher sequences: spanning thousands to tens of thousands of years), and exhibit characteristics such as rapid sedimentary facies transitions and strong heterogeneity. Frequent changes in the sedimentary environment significantly influence the development of sedimentary systems and the formation of sequence structures. These factors present new challenges for understanding the sequence architecture and sedimentary evolution in deep-water zones in lacustrine depression basins. Taking the Middle Jurassic Lianggaoshan Formation in the eastern Sichuan Basin, China, as an example, in this paper, we integrate data from cores, well logs, element geochemistry, and 3D seismic surveys. By applying the transgression–regression cycle theory and high-frequency sequence stratigraphy of lacustrine depression basins, we analyze the genetic mechanisms and distribution patterns of different types of sandstone interlayers within the shale interval and investigate the effect of high-frequency climatic changes on sedimentary processes in lacustrine basins. A high-frequency sequence pattern for lacustrine depression basins is established. The results indicate that within the third-order sequence of the Lianggaoshan Formation, during the shale-deposition interval (maximum water abundance period), the lacustrine depression basins were controlled by the 405 ka (fourth-order sequence) climatic cycle, which still demonstrates basin-scale expansion and contraction. In the shale interval, climate-driven lake transgression-regression cycles within fourth-order sequences promoted frequent interbedding of high sedimentation rate, coarse-grained deposits (e.g., deltaic deposits and hyperpycnal flow deposits) and low sedimentation rate, fine-grained deposits (e.g., suspension settling: shallow-water mudstone and deep-water shale). This reveals a high-frequency sequence stratigraphy pattern that demonstrates the coupling mechanism between the sedimentary processes and climatic forcing in lacustrine depression basins. Within the fourth-order sequences, the early transgressive systems tract and late regressive systems tract are characterized by shallow water and arid conditions, which resulted in the development of organic-poor mudstones, while deltaic sandstones prograde into the center of the basin. In contrast, the late transgressive systems tract and early regressive systems tract are marked by deep water and humid conditions, which led to the formation of organic-rich shales, accompanied by hyperpycnal flow sandstones entering the center of the basin. This resulted in the formation of multiple sets of strongly heterogeneous interbedded organic-poor mudstone and organic-rich shale assemblages. The findings establish a high-frequency sequence pattern for these basins, elucidate their internal depositional and facies evolution processes, an
{"title":"High-frequency sequence patterns in lacustrine basins: Insights from delta-hyperpycnal flow systems in the Middle Jurassic shale interval, Sichuan Basin, China","authors":"Haocheng Shi , Benzhong Xian , Yichen Liu , Zhiyun Yu , Lin Zhao , Junyang Geng , Rongheng Tian , Qianran Wu , Li Liu , Yujie Shuai , Yi Shu","doi":"10.1016/j.sedgeo.2025.106948","DOIUrl":"10.1016/j.sedgeo.2025.106948","url":null,"abstract":"<div><div>Unlike marine sedimentary basins, lacustrine sedimentary basins are more sensitive to small-scale climatic changes (fourth-order and higher sequences: spanning thousands to tens of thousands of years), and exhibit characteristics such as rapid sedimentary facies transitions and strong heterogeneity. Frequent changes in the sedimentary environment significantly influence the development of sedimentary systems and the formation of sequence structures. These factors present new challenges for understanding the sequence architecture and sedimentary evolution in deep-water zones in lacustrine depression basins. Taking the Middle Jurassic Lianggaoshan Formation in the eastern Sichuan Basin, China, as an example, in this paper, we integrate data from cores, well logs, element geochemistry, and 3D seismic surveys. By applying the transgression–regression cycle theory and high-frequency sequence stratigraphy of lacustrine depression basins, we analyze the genetic mechanisms and distribution patterns of different types of sandstone interlayers within the shale interval and investigate the effect of high-frequency climatic changes on sedimentary processes in lacustrine basins. A high-frequency sequence pattern for lacustrine depression basins is established. The results indicate that within the third-order sequence of the Lianggaoshan Formation, during the shale-deposition interval (maximum water abundance period), the lacustrine depression basins were controlled by the 405 ka (fourth-order sequence) climatic cycle, which still demonstrates basin-scale expansion and contraction. In the shale interval, climate-driven lake transgression-regression cycles within fourth-order sequences promoted frequent interbedding of high sedimentation rate, coarse-grained deposits (e.g., deltaic deposits and hyperpycnal flow deposits) and low sedimentation rate, fine-grained deposits (e.g., suspension settling: shallow-water mudstone and deep-water shale). This reveals a high-frequency sequence stratigraphy pattern that demonstrates the coupling mechanism between the sedimentary processes and climatic forcing in lacustrine depression basins. Within the fourth-order sequences, the early transgressive systems tract and late regressive systems tract are characterized by shallow water and arid conditions, which resulted in the development of organic-poor mudstones, while deltaic sandstones prograde into the center of the basin. In contrast, the late transgressive systems tract and early regressive systems tract are marked by deep water and humid conditions, which led to the formation of organic-rich shales, accompanied by hyperpycnal flow sandstones entering the center of the basin. This resulted in the formation of multiple sets of strongly heterogeneous interbedded organic-poor mudstone and organic-rich shale assemblages. The findings establish a high-frequency sequence pattern for these basins, elucidate their internal depositional and facies evolution processes, an","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"487 ","pages":"Article 106948"},"PeriodicalIF":2.9,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144889096","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}
A stromatolitic tufa with annual growth bands and a large growth rate is a promising archive for high-resolution paleoclimate reconstruction. However, a tufa formed in a fluvial setting typically lacks continuity of deposition. To obtain a continuous record, a potential study material is a cascade-type tufa growing below a waterfall. Here, we study tufas along Kobaru Beach on Tokunoshima Island, Japan, where cascade-type tufas are developed. Oxygen and carbon isotope ratios (δ18O and δ13C) of tufa samples collected from three sites with different sedimentary settings provide information about precipitation patterns and water temperature. A tufa sample from a fluvial setting exhibits clear annual growth rings, rapid growth rates, and seasonal changes in isotopic composition over approximately 20 years. Tufas of the stalagmite-type and cascade-type, having less clear annual growth rings and lower growth rates, preserve continuous records over the last 200 years, the longest record from the modern tufas. The δ13C of the cascade-type tufa shows a decreasing trend from the 1980s, which is interpreted as a result of fossil fuel consumption and an increase in rainfall. In addition, the δ13C of the cascade-type tufa tends to increase in dry intervals and decrease in humid intervals. On the other hand, an approximately 20-year periodicity is observed in the δ18O. Analysis of rainwater samples implies that the δ18O of tufa reflects the seasonality of rainfall, which is inherited from the rainwater δ18O. This interpretation is verified by the consistency between the actual record and the seasonality reconstructed by the tufa δ18O. While cascade-type tufas do not provide sub-annual resolution, they serve as valuable centennial-scale climate archives, which allow us to investigate decadal-scale climate variability, such as Pacific Decadal Oscillation.
{"title":"High-resolution isotopic records for the last 200 years from cascade tufas on Kobaru Beach, Tokunoshima Island, Japan","authors":"Akira Murata , Akihiro Kano , Aki Sakuma , Hirokazu Kato","doi":"10.1016/j.sedgeo.2025.106949","DOIUrl":"10.1016/j.sedgeo.2025.106949","url":null,"abstract":"<div><div>A stromatolitic tufa with annual growth bands and a large growth rate is a promising archive for high-resolution paleoclimate reconstruction. However, a tufa formed in a fluvial setting typically lacks continuity of deposition. To obtain a continuous record, a potential study material is a cascade-type tufa growing below a waterfall. Here, we study tufas along Kobaru Beach on Tokunoshima Island, Japan, where cascade-type tufas are developed. Oxygen and carbon isotope ratios (δ<sup>18</sup>O and δ<sup>13</sup>C) of tufa samples collected from three sites with different sedimentary settings provide information about precipitation patterns and water temperature. A tufa sample from a fluvial setting exhibits clear annual growth rings, rapid growth rates, and seasonal changes in isotopic composition over approximately 20 years. Tufas of the stalagmite-type and cascade-type, having less clear annual growth rings and lower growth rates, preserve continuous records over the last 200 years, the longest record from the modern tufas. The δ<sup>13</sup>C of the cascade-type tufa shows a decreasing trend from the 1980s, which is interpreted as a result of fossil fuel consumption and an increase in rainfall. In addition, the δ<sup>13</sup>C of the cascade-type tufa tends to increase in dry intervals and decrease in humid intervals. On the other hand, an approximately 20-year periodicity is observed in the δ<sup>18</sup>O. Analysis of rainwater samples implies that the δ<sup>18</sup>O of tufa reflects the seasonality of rainfall, which is inherited from the rainwater δ<sup>18</sup>O. This interpretation is verified by the consistency between the actual record and the seasonality reconstructed by the tufa δ<sup>18</sup>O. While cascade-type tufas do not provide sub-annual resolution, they serve as valuable centennial-scale climate archives, which allow us to investigate decadal-scale climate variability, such as Pacific Decadal Oscillation.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"487 ","pages":"Article 106949"},"PeriodicalIF":2.9,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879912","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 : 2025-08-13DOI: 10.1016/j.sedgeo.2025.106947
Gustavo Kenji Lacerda-Orita , Fernando Pérez-Valera , Jesús M. Soria , Hugo Corbí , Jingjing Liu , Núria Sierra-Ramirez , Enrique Gomez-Rivas , Luis Gibert
The Tabernas Basin (SE-Spain), renowned for its Tortonian turbidites, also records thick Messinian successions (>200 m) that offer valuable insights into the Messinian Salinity Crisis (MSC). Yet, the stratigraphic correlation of the Tabernas sediments with the classic successions of the nearby Sorbas Basin remains unclear. This study presents a composite stratigraphic section (named Yesón Alto) that covers the pre-evaporitic, syn-evaporitic, and supra-evaporitic stages of the MSC recorded in Tabernas Basin, offering detailed paleoenvironmental and chronostratigraphic characterization. We provide new constraints on the connections between two marginal basins of the Betic Cordillera and on the paleoenvironmental changes that took place in the Western Mediterranean during the MSC. During the Late Messinian pre-evaporitic phase, siltstones and shales alternating with distal turbidites recorded shifts between warm-oligotrophic and cold-eutrophic planktonic foraminiferal assemblages, indicating the influence of precession-driven climatic fluctuations on the water column. Progressive basin restriction led to the development of an incipient hybrid carbonate shelf, subjected to significant siliciclastic influx. 16 key planktonic foraminifera bioevents and a magnetic reversal (C3An.1n to C3r at 6.035 Ma) have been identified and correlated with the astronomically calibrated cycles of the Sorbas Basin, suggesting the possible synchronous onset of the MSC in both basins. The evaporitic stage in Tabernas is represented by four selenitic gypsum beds intercalated with siliciclastic and carbonate deposits. Facies analysis and gypsum isotopic compositions (δ34Ssulfate and δ18Osulfate) suggest that evaporites represent the initial cycles of the Primary Lower Gypsum (PLG) of the MSC Stage 1 in the Mediterranean. Below gypsum bed PLG 4, an inter-evaporitic level rich in marine fauna indicates the episodic re-establishment of near-normal marine conditions after periods of evaporite precipitation. The Supra-evaporitic unit, comprising deltaic-fluvial conglomerates and sandstones, reflects a regional regressive trend and marks the continentalization of the basin's margins. The progradation of these continental deposits over the evaporitic basin was favored by an eastward uplift trend in the Betic Cordillera, ultimately leading to exposure of the Tabernas Basin before or during Stages 2 and 3 of the MSC. The paleoenvironmental evolution of the Tabernas Basin indicates that marine connections with the Sorbas Basin persisted before and during the early MSC and that tectonics associated with climatic factors played a key role in the evolution of its sedimentary systems.
{"title":"A new sedimentary record from the Tabernas Basin: Implications for the Messinian Salinity Crisis in the Western Mediterranean","authors":"Gustavo Kenji Lacerda-Orita , Fernando Pérez-Valera , Jesús M. Soria , Hugo Corbí , Jingjing Liu , Núria Sierra-Ramirez , Enrique Gomez-Rivas , Luis Gibert","doi":"10.1016/j.sedgeo.2025.106947","DOIUrl":"10.1016/j.sedgeo.2025.106947","url":null,"abstract":"<div><div>The Tabernas Basin (SE-Spain), renowned for its Tortonian turbidites, also records thick Messinian successions (>200 m) that offer valuable insights into the Messinian Salinity Crisis (MSC). Yet, the stratigraphic correlation of the Tabernas sediments with the classic successions of the nearby Sorbas Basin remains unclear. This study presents a composite stratigraphic section (named Yesón Alto) that covers the pre-evaporitic, syn-evaporitic, and supra-evaporitic stages of the MSC recorded in Tabernas Basin, offering detailed paleoenvironmental and chronostratigraphic characterization. We provide new constraints on the connections between two marginal basins of the Betic Cordillera and on the paleoenvironmental changes that took place in the Western Mediterranean during the MSC. During the Late Messinian pre-evaporitic phase, siltstones and shales alternating with distal turbidites recorded shifts between warm-oligotrophic and cold-eutrophic planktonic foraminiferal assemblages, indicating the influence of precession-driven climatic fluctuations on the water column. Progressive basin restriction led to the development of an incipient hybrid carbonate shelf, subjected to significant siliciclastic influx. 16 key planktonic foraminifera bioevents and a magnetic reversal (C3An.1n to C3r at 6.035 Ma) have been identified and correlated with the astronomically calibrated cycles of the Sorbas Basin, suggesting the possible synchronous onset of the MSC in both basins. The evaporitic stage in Tabernas is represented by four selenitic gypsum beds intercalated with siliciclastic and carbonate deposits. Facies analysis and gypsum isotopic compositions (δ<sup>34</sup>S<sub>sulfate</sub> and δ<sup>18</sup>O<sub>sulfate</sub>) suggest that evaporites represent the initial cycles of the Primary Lower Gypsum (PLG) of the MSC Stage 1 in the Mediterranean. Below gypsum bed PLG 4, an inter-evaporitic level rich in marine fauna indicates the episodic re-establishment of near-normal marine conditions after periods of evaporite precipitation. The Supra-evaporitic unit, comprising deltaic-fluvial conglomerates and sandstones, reflects a regional regressive trend and marks the continentalization of the basin's margins. The progradation of these continental deposits over the evaporitic basin was favored by an eastward uplift trend in the Betic Cordillera, ultimately leading to exposure of the Tabernas Basin before or during Stages 2 and 3 of the MSC. The paleoenvironmental evolution of the Tabernas Basin indicates that marine connections with the Sorbas Basin persisted before and during the early MSC and that tectonics associated with climatic factors played a key role in the evolution of its sedimentary systems.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"487 ","pages":"Article 106947"},"PeriodicalIF":2.9,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144865276","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 : 2025-08-07DOI: 10.1016/j.sedgeo.2025.106946
Yi-Xi Wen , Ze-Min Xu , Xiao Su , Bin Li , Zi-Ming Ye , Gui-E Shi , Jing-Kai Meng
Sediments related to debris flows consist usually of single clasts of various sizes. A kind of composite debris, i.e., elongate debris aggregates, occurring in the Jiangjia Gully debris flows in China, is reported herein. They can occur as isolated individuals, and more commonly as clusters of a few to several hundred individuals. 2,225 measured aggregates vary in maximum and minimum dimensions from 2 to 187 cm (average 17 cm) and from 2 to 107 cm (mean 12 cm), respectively. The aggregates with an elongation ratio of ≤ 0.8 make up 63%, fat ones having a flatness ratio of ≤ 0.8 represents only 37%, and at least 53% of the aggregates are prolate spheroidal. The average convexity of 0.92 illustrates that the aggregate surfaces are smooth. Massive structure (sometimes with cobble cores), concentrically banded structure, and deformation structure are developed in aggregate interiors. Slate clasts ranging in size from clay to cobbles, which originate from landslide debris in the debris-flow source areas and moving debris-flow slurries, comprise the aggregates. Field observations of more than 30 surges show that most of the aggregates belong to the objects transported by the debris flows, and rolling process is essential to their development. Fibrous palygorskite, which acts as the rock-forming mineral of the slate bedrock and is released by slate detritus, is responsible for the widespread occurrence of the aggregates. The marked presence of the elongate aggregates indicates that the debris flows can be approximated as one-dimensional, laminar flow of homogeneous single-phase yield stress fluids. Debris aggregates in debris flows merit attention because of their significant implications for debris-flow dynamics and of facilitating sediment transfer.
{"title":"Debris aggregates in debris flows and implications for debris-flow dynamics","authors":"Yi-Xi Wen , Ze-Min Xu , Xiao Su , Bin Li , Zi-Ming Ye , Gui-E Shi , Jing-Kai Meng","doi":"10.1016/j.sedgeo.2025.106946","DOIUrl":"10.1016/j.sedgeo.2025.106946","url":null,"abstract":"<div><div>Sediments related to debris flows consist usually of single clasts of various sizes. A kind of composite debris, i.e., elongate debris aggregates, occurring in the Jiangjia Gully debris flows in China, is reported herein. They can occur as isolated individuals, and more commonly as clusters of a few to several hundred individuals. 2,225 measured aggregates vary in maximum and minimum dimensions from 2 to 187 cm (average 17 cm) and from 2 to 107 cm (mean 12 cm), respectively. The aggregates with an elongation ratio of ≤ 0.8 make up 63%, fat ones having a flatness ratio of ≤ 0.8 represents only 37%, and at least 53% of the aggregates are prolate spheroidal. The average convexity of 0.92 illustrates that the aggregate surfaces are smooth. Massive structure (sometimes with cobble cores), concentrically banded structure, and deformation structure are developed in aggregate interiors. Slate clasts ranging in size from clay to cobbles, which originate from landslide debris in the debris-flow source areas and moving debris-flow slurries, comprise the aggregates. Field observations of more than 30 surges show that most of the aggregates belong to the objects transported by the debris flows, and rolling process is essential to their development. Fibrous palygorskite, which acts as the rock-forming mineral of the slate bedrock and is released by slate detritus, is responsible for the widespread occurrence of the aggregates. The marked presence of the elongate aggregates indicates that the debris flows can be approximated as one-dimensional, laminar flow of homogeneous single-phase yield stress fluids. Debris aggregates in debris flows merit attention because of their significant implications for debris-flow dynamics and of facilitating sediment transfer.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"488 ","pages":"Article 106946"},"PeriodicalIF":2.9,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912003","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 : 2025-08-05DOI: 10.1016/j.sedgeo.2025.106944
Sten-Andreas Grundvåg , Gijs A. Henstra , Atle Rotevatn , Eric Salomon , Thomas Berg Kristensen
Supercritical high-density turbidity currents descending steep submarine slopes often transition to subcritical flow via hydraulic jumps at the base-of-slope break, causing scouring and plunge pool formation. On the slope, scour arrays from turbulent erosion by the flow head, can develop into chutes where supercritical flow is sustained, generating cyclic steps. However, little is known about the infill of hydraulic-jump-related scours and upper flow regime bedforms in coarse-grained, deep-water slope systems. This study examines conglomerate- and sandstone-rich sediment gravity flow deposits from an Upper Jurassic–Lower Cretaceous deep-water syn-rift succession in Wollaston Forland, NE Greenland. These coarse-grained deposits accumulated on a steep, subaqueous fan delta slope perched on the basin-bounding fault escarpment. The upper slope, with minimal scouring, is dominated by breccia and conglomerate beds from debris falls and non-cohesive debris flows. In contrast, the lower slope exhibits extensive scouring, diverse scour-and-fill elements, and complex bedding patterns suggesting hydraulic jump-related erosion and scour filling by strongly stratified, supercritical high-density turbidity currents. Arrays of asymmetric conglomeratic scour fills, frequently exhibiting variably inclined and laterally accreted stratification, may indicate the presence of cyclic steps. Abundant conglomerate-filled scours at the slope base further suggest that gravel from the basal, inertia-driven part of the flows were trapped in plunge pools carved by their faster-moving turbulent parts. The dominance of sandstone beds on the basin floor indicates that the sand-laden turbulent flows continued basinward before coming to rest. Our findings highlight the role of flow transformation and scouring in shaping submarine slopes and controlling deep-water architecture.
{"title":"Signatures of hydraulic jump-related scouring in a deep-marine rift basin, Wollaston Forland Group, NE Greenland","authors":"Sten-Andreas Grundvåg , Gijs A. Henstra , Atle Rotevatn , Eric Salomon , Thomas Berg Kristensen","doi":"10.1016/j.sedgeo.2025.106944","DOIUrl":"10.1016/j.sedgeo.2025.106944","url":null,"abstract":"<div><div>Supercritical high-density turbidity currents descending steep submarine slopes often transition to subcritical flow via hydraulic jumps at the base-of-slope break, causing scouring and plunge pool formation. On the slope, scour arrays from turbulent erosion by the flow head, can develop into chutes where supercritical flow is sustained, generating cyclic steps. However, little is known about the infill of hydraulic-jump-related scours and upper flow regime bedforms in coarse-grained, deep-water slope systems. This study examines conglomerate- and sandstone-rich sediment gravity flow deposits from an Upper Jurassic–Lower Cretaceous deep-water <em>syn</em>-rift succession in Wollaston Forland, NE Greenland. These coarse-grained deposits accumulated on a steep, subaqueous fan delta slope perched on the basin-bounding fault escarpment. The upper slope, with minimal scouring, is dominated by breccia and conglomerate beds from debris falls and non-cohesive debris flows. In contrast, the lower slope exhibits extensive scouring, diverse scour-and-fill elements, and complex bedding patterns suggesting hydraulic jump-related erosion and scour filling by strongly stratified, supercritical high-density turbidity currents. Arrays of asymmetric conglomeratic scour fills, frequently exhibiting variably inclined and laterally accreted stratification, may indicate the presence of cyclic steps. Abundant conglomerate-filled scours at the slope base further suggest that gravel from the basal, inertia-driven part of the flows were trapped in plunge pools carved by their faster-moving turbulent parts. The dominance of sandstone beds on the basin floor indicates that the sand-laden turbulent flows continued basinward before coming to rest. Our findings highlight the role of flow transformation and scouring in shaping submarine slopes and controlling deep-water architecture.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"487 ","pages":"Article 106944"},"PeriodicalIF":2.9,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144865275","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}
Conventional cores collected from a shallow tropical carbonate-ramp system reflect a diagenetic pathway that was influenced by both the globally humid, tropical climate at the middle Eocene time and the subsequent onset of Himalayan mountain building. Detailed optical, cathodoluminescence-petrographic and non-isotopic geochemical analyses were used for the study. The eogenetic processes, e.g., micritization, pyritization, isopachous and micritic cementation, early marine dolomitization, and the early stages of mechanical compaction, happened during and soon after deposition in the marine-phreatic environment. During the late Eocene, as the global climate cooled, the relative sea level fell, and the carbonate ramp underwent subaerial exposure, leading to the meteoric-phreatic diagenetic processes, e.g., neomorphism, dissolution (phase-1), pendant cementation (vadose zone), and significant calcite spar cementation (C-1). With ensuing deposition above through the early Oligocene, the effects of compaction affected the formation by truncation and fragmentation of grains, condensed packing, developing various (point-tangential, concavo-convex, and sutured) grain contacts, pressure dissolution and stylolite generation, fracturing, corrosion (phase-2 dissolution), and burial-calcitic (C-2) and non-calcitic (NC) cementation. After the early Oligocene, the basin tilted westward, a far-field consequence of the Indo-Eurasian collision. This tectonic reorganisation caused the Paleogene carbonate strata to undergo a partial exhumation and thus, they were susceptible to the influence of meteoric water mainly through the reactivation of pre-existing faults. These tectonic readjustments led to the reopening of the stylolite sets, telogenetic fracturing, and another dissolution episode (phase 3). Hence, the diagenetic pathway manifesting itself at the microscopic scale posits a clear connection with the basin's evolution. Further, the diagenetic reconstruction also corroborates the global climatic transition, from a greenhouse to a cooler ice-house condition, that took place across the Eocene-Oligocene boundary, making the study significant from a regional to global scale.
{"title":"From Platform to Burial: Tectonic and climatic imprints on the diagenetic evolution of shallow-marine carbonate deposits (Middle Eocene), Bombay Offshore Basin, India","authors":"Sreetama Aich , Cathy Hollis , Sudipta Dasgupta , Kumar Hemant Singh","doi":"10.1016/j.sedgeo.2025.106940","DOIUrl":"10.1016/j.sedgeo.2025.106940","url":null,"abstract":"<div><div>Conventional cores collected from a shallow tropical carbonate-ramp system reflect a diagenetic pathway that was influenced by both the globally humid, tropical climate at the middle Eocene time and the subsequent onset of Himalayan mountain building. Detailed optical, cathodoluminescence-petrographic and non-isotopic geochemical analyses were used for the study. The eogenetic processes, e.g., micritization, pyritization, isopachous and micritic cementation, early marine dolomitization, and the early stages of mechanical compaction, happened during and soon after deposition in the marine-phreatic environment. During the late Eocene, as the global climate cooled, the relative sea level fell, and the carbonate ramp underwent subaerial exposure, leading to the meteoric-phreatic diagenetic processes, e.g., neomorphism, dissolution (phase-1), pendant cementation (vadose zone), and significant calcite spar cementation (C-1). With ensuing deposition above through the early Oligocene, the effects of compaction affected the formation by truncation and fragmentation of grains, condensed packing, developing various (point-tangential, concavo-convex, and sutured) grain contacts, pressure dissolution and stylolite generation, fracturing, corrosion (phase-2 dissolution), and burial-calcitic (C-2) and non-calcitic (NC) cementation. After the early Oligocene, the basin tilted westward, a far-field consequence of the Indo-Eurasian collision. This tectonic reorganisation caused the Paleogene carbonate strata to undergo a partial exhumation and thus, they were susceptible to the influence of meteoric water mainly through the reactivation of pre-existing faults. These tectonic readjustments led to the reopening of the stylolite sets, telogenetic fracturing, and another dissolution episode (phase 3). Hence, the diagenetic pathway manifesting itself at the microscopic scale posits a clear connection with the basin's evolution. Further, the diagenetic reconstruction also corroborates the global climatic transition, from a greenhouse to a cooler ice-house condition, that took place across the Eocene-Oligocene boundary, making the study significant from a regional to global scale.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"488 ","pages":"Article 106940"},"PeriodicalIF":2.9,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144916613","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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