Jeffery M. Valenza, Douglas A. Edmonds, Harrison K. Martin, Caitlin Sifuentes, Stephan Toby
Natural river diversion, or avulsion, controls the distribution of channels on a floodplain and channel sandstone bodies within fluvial stratigraphic architecture. Avulsions establish new flow paths and create channels through several recognized processes, or styles. These include reoccupying existing channels, or annexation, downcutting into the floodplain, or incision, and constructing new channels from crevasse‐splay distributary networks, or progradation. Recent remote sensing observations show that avulsion style changes systematically moving downstream along modern fluvial fans but, to date, no studies have assessed the significance of these trends on fluvial fan stratigraphy. Here, spatiotemporal changes in avulsion stratigraphy are investigated within the Salt Wash Member of the Morrison Formation, deposited in the Cordilleran foreland basin during the Late Jurassic epoch. Measured sections and photographic panels were analysed from 23 locations across the Salt Wash extent. Avulsion style was identified in the stratigraphic record by the basal contact of a channel storey with underlying strata: channel–channel contacts indicate annexation, channel–floodplain contacts indicate incision and channel–heterolithic contacts indicate progradation. Contact types change downstream, such that channel–channel and channel–floodplain contacts dominate proximal locations, while channel–heterolithic contacts become increasingly prevalent downstream. Outcrop results were compared to a numerical model of fluvial fan formation and remote‐sensing analysis of avulsions on modern fans. In both additional datasets, channels in proximal fan positions tend to avulse via annexation, reoccupying abandoned channels, while channels in more distal positions tend to avulse via increasingly significant progradation. These findings suggest a relationship between newly recognized downstream changes in avulsion style and well‐established downstream changes in fluvial fan architecture. Furthermore, this suggests that fan architecture can inform interpretations of ancient fluvial dynamics, including avulsion behaviour, and that avulsions can cause stratigraphically significant and measurable changes to fan architecture.
{"title":"Stratigraphic architecture of fluvial fans shaped by downstream changes in avulsion style","authors":"Jeffery M. Valenza, Douglas A. Edmonds, Harrison K. Martin, Caitlin Sifuentes, Stephan Toby","doi":"10.1111/sed.13217","DOIUrl":"https://doi.org/10.1111/sed.13217","url":null,"abstract":"Natural river diversion, or avulsion, controls the distribution of channels on a floodplain and channel sandstone bodies within fluvial stratigraphic architecture. Avulsions establish new flow paths and create channels through several recognized processes, or styles. These include reoccupying existing channels, or annexation, downcutting into the floodplain, or incision, and constructing new channels from crevasse‐splay distributary networks, or progradation. Recent remote sensing observations show that avulsion style changes systematically moving downstream along modern fluvial fans but, to date, no studies have assessed the significance of these trends on fluvial fan stratigraphy. Here, spatiotemporal changes in avulsion stratigraphy are investigated within the Salt Wash Member of the Morrison Formation, deposited in the Cordilleran foreland basin during the Late Jurassic epoch. Measured sections and photographic panels were analysed from 23 locations across the Salt Wash extent. Avulsion style was identified in the stratigraphic record by the basal contact of a channel storey with underlying strata: channel–channel contacts indicate annexation, channel–floodplain contacts indicate incision and channel–heterolithic contacts indicate progradation. Contact types change downstream, such that channel–channel and channel–floodplain contacts dominate proximal locations, while channel–heterolithic contacts become increasingly prevalent downstream. Outcrop results were compared to a numerical model of fluvial fan formation and remote‐sensing analysis of avulsions on modern fans. In both additional datasets, channels in proximal fan positions tend to avulse via annexation, reoccupying abandoned channels, while channels in more distal positions tend to avulse via increasingly significant progradation. These findings suggest a relationship between newly recognized downstream changes in avulsion style and well‐established downstream changes in fluvial fan architecture. Furthermore, this suggests that fan architecture can inform interpretations of ancient fluvial dynamics, including avulsion behaviour, and that avulsions can cause stratigraphically significant and measurable changes to fan architecture.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"20 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742232","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}
Mariza Gomes Rodrigues, Filipe Giovanini Varejão, Franz Theodor Fürsich, Beatriz Christofoletti, Suzana Aparecida Matos, Lucas Veríssimo Warren, Lucas Inglez, Rodrigo Irineu Cerri, Mario Luis Assine, Marcello Guimarães Simões
Event deposition accounts for a large part of the preserved sedimentary record. Tempestites, tsunamites and turbidites are among the most common event deposits in marine and lacustrine systems. While facies models exist for these deposits, the challenge lies in the fact that diverse triggers can give rise to analogous depositional processes and comparable taphonomic features, making it difficult to pinpoint the precise trigger for an event bed. Hence, five distinct modern‐type shell concentrations are studied in Permian strata from the Paraná Basin, West Gondwana, to access the parameters to discriminate event phenomena, and their associated depositional and taphonomic processes. During this time interval, the basin underwent continuous continentalization due to orogenic events, leading to the entrapment of epeiric marine waters and the transformation of the system into a megalake, supporting a diverse and endemic freshwater bivalve fauna. While sedimentation was primarily influenced by meteorological events, certain stratigraphic intervals were also affected by tectonically active periods and meteor impact events. The different products are categorized into bioclastic sandstone, shell bed, shell‐rich phosclast rudstone and shell‐rich conglomerate that are interpreted as proximal and distal tempestites and tsunamites, respectively. Finally, the products and the processes that lead to the deposition of tempestites and tsunamites are compared to establish diagnostic signatures that may be applied to differentiate these event concentrations in analogous settings from the geological record.
{"title":"Not all shell beds are made equal: Recognizing singular event‐concentrations in megalakes","authors":"Mariza Gomes Rodrigues, Filipe Giovanini Varejão, Franz Theodor Fürsich, Beatriz Christofoletti, Suzana Aparecida Matos, Lucas Veríssimo Warren, Lucas Inglez, Rodrigo Irineu Cerri, Mario Luis Assine, Marcello Guimarães Simões","doi":"10.1111/sed.13221","DOIUrl":"https://doi.org/10.1111/sed.13221","url":null,"abstract":"Event deposition accounts for a large part of the preserved sedimentary record. Tempestites, tsunamites and turbidites are among the most common event deposits in marine and lacustrine systems. While facies models exist for these deposits, the challenge lies in the fact that diverse triggers can give rise to analogous depositional processes and comparable taphonomic features, making it difficult to pinpoint the precise trigger for an event bed. Hence, five distinct modern‐type shell concentrations are studied in Permian strata from the Paraná Basin, West Gondwana, to access the parameters to discriminate event phenomena, and their associated depositional and taphonomic processes. During this time interval, the basin underwent continuous continentalization due to orogenic events, leading to the entrapment of epeiric marine waters and the transformation of the system into a megalake, supporting a diverse and endemic freshwater bivalve fauna. While sedimentation was primarily influenced by meteorological events, certain stratigraphic intervals were also affected by tectonically active periods and meteor impact events. The different products are categorized into bioclastic sandstone, shell bed, shell‐rich phosclast rudstone and shell‐rich conglomerate that are interpreted as proximal and distal tempestites and tsunamites, respectively. Finally, the products and the processes that lead to the deposition of tempestites and tsunamites are compared to establish diagnostic signatures that may be applied to differentiate these event concentrations in analogous settings from the geological record.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"55 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141576874","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}
Fan Meng, Zhong Han, Xiumian Hu, Hugh C. Jenkyns, Bolin Zhang, Xi Chen, Mingcai Hou
Mesozoic oceanic anoxic events were characterized by relatively low seawater sulphate concentrations ([]), which likely regulated the development and evolution of these major palaeoceanographic phenomena. However, there is little reliable sedimentary evidence for low [] in ancient marine waters and understanding of how such a seawater chemistry potentially impacted oceanic anoxic events is limited. This study presents an integrated sedimentological, mineralogical and geochemical investigation of the mineral siderite hosted in dark grey shale and sideritic concretions of Early Aptian (coeval with Oceanic Anoxic Event 1a) from the Tibetan Himalaya. Siderite is present throughout the section and possesses similar morphological characteristics whether in dark grey shale or concretions. Siderite can be present as disseminated and rhombic crystals formed during early diagenesis, or minor spherical crystals formed during late diagenesis. The evidence from redox elements, middle rare‐earth element bulge patterns and extremely low carbon‐isotope values of the sideritic concretions indicates that the iron carbonate was formed in the Fe‐reduction zones by the process of dissimilatory iron reduction. This process would have required conditions of low [], reducing environment, abundant iron and high alkalinity. Additionally, the coexistence of siderite and pyrite may indicate that dissimilatory iron reduction occurred close to the microbial sulphate reduction zone, with seawater [] hovering around the tipping point at which pyrite could form once seawater sulphate increased. Such an increase during Oceanic Anoxic Event 1a could have resulted from basalt–seawater interaction and associated enhanced continental weathering, and/or hydrothermal activity. This study's observations support the previous hypothesis that low [] for Oceanic Anoxic Event 1a was probably caused by massive gypsum burial in the proto‐South Atlantic. Subsequently, enhanced sulphate input could have promoted microbial sulphate reduction and accompanying oxidation of organic matter, which likely further enhanced nutrient recycling, increased primary productivity and organic‐carbon burial, leading to more oxygen consumption and expansion of oxygen minimum zones, as reconstructed for many oceanic anoxic events.
{"title":"Siderite from the Tibetan Himalaya: Evidence for a low sulphate ocean during Oceanic Anoxic Event 1a (Early Aptian)","authors":"Fan Meng, Zhong Han, Xiumian Hu, Hugh C. Jenkyns, Bolin Zhang, Xi Chen, Mingcai Hou","doi":"10.1111/sed.13218","DOIUrl":"https://doi.org/10.1111/sed.13218","url":null,"abstract":"Mesozoic oceanic anoxic events were characterized by relatively low seawater sulphate concentrations ([]), which likely regulated the development and evolution of these major palaeoceanographic phenomena. However, there is little reliable sedimentary evidence for low [] in ancient marine waters and understanding of how such a seawater chemistry potentially impacted oceanic anoxic events is limited. This study presents an integrated sedimentological, mineralogical and geochemical investigation of the mineral siderite hosted in dark grey shale and sideritic concretions of Early Aptian (coeval with Oceanic Anoxic Event 1a) from the Tibetan Himalaya. Siderite is present throughout the section and possesses similar morphological characteristics whether in dark grey shale or concretions. Siderite can be present as disseminated and rhombic crystals formed during early diagenesis, or minor spherical crystals formed during late diagenesis. The evidence from redox elements, middle rare‐earth element bulge patterns and extremely low carbon‐isotope values of the sideritic concretions indicates that the iron carbonate was formed in the Fe‐reduction zones by the process of dissimilatory iron reduction. This process would have required conditions of low [], reducing environment, abundant iron and high alkalinity. Additionally, the coexistence of siderite and pyrite may indicate that dissimilatory iron reduction occurred close to the microbial sulphate reduction zone, with seawater [] hovering around the tipping point at which pyrite could form once seawater sulphate increased. Such an increase during Oceanic Anoxic Event 1a could have resulted from basalt–seawater interaction and associated enhanced continental weathering, and/or hydrothermal activity. This study's observations support the previous hypothesis that low [] for Oceanic Anoxic Event 1a was probably caused by massive gypsum burial in the proto‐South Atlantic. Subsequently, enhanced sulphate input could have promoted microbial sulphate reduction and accompanying oxidation of organic matter, which likely further enhanced nutrient recycling, increased primary productivity and organic‐carbon burial, leading to more oxygen consumption and expansion of oxygen minimum zones, as reconstructed for many oceanic anoxic events.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"78 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141576875","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}
Joaquín Bucher, Cecilia del Papa, Irene R. Hernando, Gabriela Almada
Supercritical flows and their associated upper‐flow‐regime bedforms have been increasingly recognized in several contrasting depositional environments around the world, including volcano‐sedimentary settings. In recent years, there have been significant advances in flow modelling, architecture and depositional dynamics in upper‐flow‐regime bedforms related to glacio‐volcanic interaction, however most of these works come from specific volcanic landscapes. Examples of other regions with different tectonic and volcanic settings are needed in order to gain a more global perspective regarding the generation and preservation of upper‐flow‐regime glacio‐volcanic bedforms. This study presents a detailed analysis of Pleistocene volcaniclastic deposits accumulated in alluvial to lacustrine deltaic environments in the Southern Andes within the Southern Volcanic Zone. Six facies were defined and related to distinctive bedforms by examining sedimentary features, including textural characteristics, sedimentary structures, architecture and composition. Among these facies, five are distinguished by deposition from supercritical flows and upper‐flow‐regime bedforms, such as cyclic steps, chutes and pools, and antidunes. The stratigraphic succession reveals a predominance of repeated supercritical flows, which appear to be influenced by the availability of detritus for removal along with sudden water discharges. Compositional analyses indicate that explosive volcanism was the primary source of detritus, occurring synchronously with sedimentation. Additionally, the widespread occurrence of Pleistocene glacial conditions in this region suggests that volcanic‐induced melting ice or snow may have been an important source of water supply. Regarding the Southern Andes, the presence of local depressions, such as volcano‐tectonic calderas plays an essential role in the generation and preservation of the upper‐flow‐regime bedforms related to glacio‐volcanism. Furthermore, the importance of carrying out detailed and multidisciplinary studies seems to be critical for the recognition of these deposits in the record of the Andes.
{"title":"Upper‐flow‐regime deposits related to glacio‐volcanic interactions in Patagonia: Insights from the Pleistocene record in Southern Andes","authors":"Joaquín Bucher, Cecilia del Papa, Irene R. Hernando, Gabriela Almada","doi":"10.1111/sed.13216","DOIUrl":"https://doi.org/10.1111/sed.13216","url":null,"abstract":"Supercritical flows and their associated upper‐flow‐regime bedforms have been increasingly recognized in several contrasting depositional environments around the world, including volcano‐sedimentary settings. In recent years, there have been significant advances in flow modelling, architecture and depositional dynamics in upper‐flow‐regime bedforms related to glacio‐volcanic interaction, however most of these works come from specific volcanic landscapes. Examples of other regions with different tectonic and volcanic settings are needed in order to gain a more global perspective regarding the generation and preservation of upper‐flow‐regime glacio‐volcanic bedforms. This study presents a detailed analysis of Pleistocene volcaniclastic deposits accumulated in alluvial to lacustrine deltaic environments in the Southern Andes within the Southern Volcanic Zone. Six facies were defined and related to distinctive bedforms by examining sedimentary features, including textural characteristics, sedimentary structures, architecture and composition. Among these facies, five are distinguished by deposition from supercritical flows and upper‐flow‐regime bedforms, such as cyclic steps, chutes and pools, and antidunes. The stratigraphic succession reveals a predominance of repeated supercritical flows, which appear to be influenced by the availability of detritus for removal along with sudden water discharges. Compositional analyses indicate that explosive volcanism was the primary source of detritus, occurring synchronously with sedimentation. Additionally, the widespread occurrence of Pleistocene glacial conditions in this region suggests that volcanic‐induced melting ice or snow may have been an important source of water supply. Regarding the Southern Andes, the presence of local depressions, such as volcano‐tectonic calderas plays an essential role in the generation and preservation of the upper‐flow‐regime bedforms related to glacio‐volcanism. Furthermore, the importance of carrying out detailed and multidisciplinary studies seems to be critical for the recognition of these deposits in the record of the Andes.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"24 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548319","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}
Justin B. R. Drummond, Peir K. Pufahl, Noel P. James, Daniel Layton‐Matthews, T. Kurt Kyser
Quaternary to Recent sedimentary dolomite in groundwater calcrete and saltmarsh sediments of Lake Way and Lake Maitland, Western Australia, provide new information about the formation of low‐temperature dolomite. Dolomite can form through numerous pathways depending on the depositional and diagenetic environment. Many pathways involve microbial processes and/or the presence of a nucleation substrate which help overcome kinetic barriers preventing precipitation in the laboratory. Petrographic, mineralogical, hydrogeochemical and stable isotopic data in this study reveal the importance of Mg‐clays as nucleation sites for dolomite precipitation in a range of aquifer environments. There is also a close association between authigenic Mg‐clays, dolomite and the potassium–uranyl–vanadate ore mineral carnotite in channel and playa uranium deposits. It is interpreted that evaporation‐driven precipitation of dolomite establishes a positive feedback loop promoting the dissociation of aqueous uranyl–carbonate complexes and concomitant increase in carnotite saturation. Critical to this model is the presence of authigenic Mg‐clays because they facilitate dolomite precipitation and promote carnotite nucleation by concentrating potassium ions on clay surfaces via adsorption. This Mg‐clay–dolomite–carnotite relationship is widespread throughout Western Australian channel and playa uranium deposits and has been observed in similar deposits in Namibia and Botswana. In addition to this economic implication, Mg‐clay mediated nucleation of dolomite potentially has global relevance as a precipitation mechanism for low temperature dolomite in sedimentary deposits where detrital and/or authigenic Mg‐clays are present. Maturation of sedimentary dolomite from disordered high‐calcian dolomite to ordered low‐calcian dolomite occurs very early in the meteoric realm making it resistant to alteration during burial diagenesis. Diagenetic resistance may be further increased by early meteoric silicification related to the degradation of associated Mg‐clays. These findings indicate that Mg‐clay associated sedimentary dolomite has potential to retain a primary isotopic signature indicative of its origin, making it a useful recorder of palaeoenvironmental conditions.
{"title":"Sedimentary dolomite in Western Australia and the dolomite problem: Genesis of channel and playa uranium deposits","authors":"Justin B. R. Drummond, Peir K. Pufahl, Noel P. James, Daniel Layton‐Matthews, T. Kurt Kyser","doi":"10.1111/sed.13214","DOIUrl":"https://doi.org/10.1111/sed.13214","url":null,"abstract":"Quaternary to Recent sedimentary dolomite in groundwater calcrete and saltmarsh sediments of Lake Way and Lake Maitland, Western Australia, provide new information about the formation of low‐temperature dolomite. Dolomite can form through numerous pathways depending on the depositional and diagenetic environment. Many pathways involve microbial processes and/or the presence of a nucleation substrate which help overcome kinetic barriers preventing precipitation in the laboratory. Petrographic, mineralogical, hydrogeochemical and stable isotopic data in this study reveal the importance of Mg‐clays as nucleation sites for dolomite precipitation in a range of aquifer environments. There is also a close association between authigenic Mg‐clays, dolomite and the potassium–uranyl–vanadate ore mineral carnotite in channel and playa uranium deposits. It is interpreted that evaporation‐driven precipitation of dolomite establishes a positive feedback loop promoting the dissociation of aqueous uranyl–carbonate complexes and concomitant increase in carnotite saturation. Critical to this model is the presence of authigenic Mg‐clays because they facilitate dolomite precipitation and promote carnotite nucleation by concentrating potassium ions on clay surfaces via adsorption. This Mg‐clay–dolomite–carnotite relationship is widespread throughout Western Australian channel and playa uranium deposits and has been observed in similar deposits in Namibia and Botswana. In addition to this economic implication, Mg‐clay mediated nucleation of dolomite potentially has global relevance as a precipitation mechanism for low temperature dolomite in sedimentary deposits where detrital and/or authigenic Mg‐clays are present. Maturation of sedimentary dolomite from disordered high‐calcian dolomite to ordered low‐calcian dolomite occurs very early in the meteoric realm making it resistant to alteration during burial diagenesis. Diagenetic resistance may be further increased by early meteoric silicification related to the degradation of associated Mg‐clays. These findings indicate that Mg‐clay associated sedimentary dolomite has potential to retain a primary isotopic signature indicative of its origin, making it a useful recorder of palaeoenvironmental conditions.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"18 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518563","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}
Elizabeth Chacón‐Baca, Oscar Romero de la Cruz, Gabriel Chavez‐Cabello, Edith Cienfuegos Alvarado, Pedro Morales‐Puente, Leticia Alba‐Aldave, Saul Blanco Lanza
Cuatro Cienegas is a natural geopark that exhibits a vast reservoir of geological, geochemical and geobiological diversity, including shallow‐water microbial carbonates with clotted micrite textures known as thrombolites. Thrombolites mainly occur as domes and massive irregular carbonates along the margins of Rio Mezquites in Cuatro Cienegas, northern Mexico. Because their clotted textures result from diverse abiotic and biotic interactions at the microbial–mineral interface, the formation of clots in thrombolites continues to be a contentious issue. Through a petrographic, scanning electron microscopy and bulk biogeochemical analysis, this study investigated the role of endolithic cyanobacteria in the generation of thrombolitic clots. Their microclotted fabric is characterized by 50 to 200 μm peloidal clots, pores, fenestrae, crevices and cavities as main components. Thrombolites also contain microbial microstructures, some of them interpreted as the endolithic contribution to the genesis of clotted micrite. Thrombolites and associated fresh microbial mats are composed of cyanobacteria, green algae and diatoms. Petrography and cast‐embedded scanning electron microscopy micrographs also show the presence of filamentous endolithic cyanobacteria inside the thrombolitic framestone. The geochemical bulk characterization for carbon and oxygen isotopes shows average values of −0.7‰ Vienna PeeDee Belemnite and −8.0‰ Vienna PeeDee Belemnite, respectively. The organic matter preserved in their mineral matrix and associated microbial mats indicated the putative presence of cyanobacterial hopanoids. The high diversity of peloids and the microboring evidence, together with observed microstructures, suggest that clots may also form by the concurrent precipitation and dissolution of the thrombolites. Among the known sources of peloidal clots, microbial boring may be an additional micrite source for clot formation. Microbial carbonate dissolution may also promote heterogenous lithification by hydration and dehydration cycles. Thrombolites reflect complex systems due to concurrent interactions among producers (phototrophs), consumers (small invertebrates), mineralization (carbonate precipitation induced by phototrophs) and endolithic dissolution. The microstructures inside thrombolites, in conjunction with biogeochemical attributes of bulk thrombolites, may provide unambiguous sedimentary biosignatures.
Cuatro Cienegas 是一个天然地质公园，拥有丰富的地质、地球化学和地球生物多样性，其中包括具有凝块微晶质地的浅水微生物碳酸盐岩，即血栓岩。血栓岩主要以圆顶和块状不规则碳酸盐的形式出现在墨西哥北部 Cuatro Cienegas 的 Rio Mezquites 边缘。由于它们的凝块纹理是微生物-矿物界面上各种非生物和生物相互作用的结果，因此血栓岩中凝块的形成仍然是一个有争议的问题。本研究通过岩相学、扫描电子显微镜和大体积生物地球化学分析，研究了内生蓝藻在血栓质凝块生成过程中的作用。其微凝块结构的特点是以 50 至 200 μm 的球状凝块、孔隙、栅栏、裂缝和空腔为主要成分。血栓岩中还含有微生物微结构，其中一些被解释为内生岩对凝块微晶岩成因的贡献。血栓岩和相关的新鲜微生物垫由蓝藻、绿藻和硅藻组成。岩相学和铸造嵌入式扫描电子显微镜显微照片还显示，血栓框架石内部存在丝状内生蓝藻。碳同位素和氧同位素的地球化学大体特征显示，其平均值分别为-0.7‰维也纳皮迪白云石和-8.0‰维也纳皮迪白云石。其矿物基质和相关微生物垫中保存的有机物表明可能存在蓝藻类。球粒体的高度多样性和微孔证据以及观察到的微观结构表明，凝块也可能是通过同时沉淀和溶解血栓沸石而形成的。在已知的球状凝块来源中，微生物乏味可能是凝块形成的另一个微晶来源。微生物碳酸盐溶解也可能通过水化和脱水循环促进异质岩化。血栓岩反映了生产者（光养生物）、消费者（小型无脊椎动物）、矿化（光养生物诱导的碳酸盐沉淀）和内溶石之间同时发生相互作用的复杂系统。血栓岩内部的微观结构与块状血栓岩的生物地球化学属性相结合，可提供明确的沉积生物特征。
{"title":"The generation of a clotted peloidal micrite fabric by endolithic cyanobacteria in recent thrombolites from Cuatro Cienegas, northern Mexico","authors":"Elizabeth Chacón‐Baca, Oscar Romero de la Cruz, Gabriel Chavez‐Cabello, Edith Cienfuegos Alvarado, Pedro Morales‐Puente, Leticia Alba‐Aldave, Saul Blanco Lanza","doi":"10.1111/sed.13215","DOIUrl":"https://doi.org/10.1111/sed.13215","url":null,"abstract":"Cuatro Cienegas is a natural geopark that exhibits a vast reservoir of geological, geochemical and geobiological diversity, including shallow‐water microbial carbonates with clotted micrite textures known as thrombolites. Thrombolites mainly occur as domes and massive irregular carbonates along the margins of Rio Mezquites in Cuatro Cienegas, northern Mexico. Because their clotted textures result from diverse abiotic and biotic interactions at the microbial–mineral interface, the formation of clots in thrombolites continues to be a contentious issue. Through a petrographic, scanning electron microscopy and bulk biogeochemical analysis, this study investigated the role of endolithic cyanobacteria in the generation of thrombolitic clots. Their microclotted fabric is characterized by 50 to 200 μm peloidal clots, pores, fenestrae, crevices and cavities as main components. Thrombolites also contain microbial microstructures, some of them interpreted as the endolithic contribution to the genesis of clotted micrite. Thrombolites and associated fresh microbial mats are composed of cyanobacteria, green algae and diatoms. Petrography and cast‐embedded scanning electron microscopy micrographs also show the presence of filamentous endolithic cyanobacteria inside the thrombolitic framestone. The geochemical bulk characterization for carbon and oxygen isotopes shows average values of −0.7‰ Vienna PeeDee Belemnite and −8.0‰ Vienna PeeDee Belemnite, respectively. The organic matter preserved in their mineral matrix and associated microbial mats indicated the putative presence of cyanobacterial hopanoids. The high diversity of peloids and the microboring evidence, together with observed microstructures, suggest that clots may also form by the concurrent precipitation and dissolution of the thrombolites. Among the known sources of peloidal clots, microbial boring may be an additional micrite source for clot formation. Microbial carbonate dissolution may also promote heterogenous lithification by hydration and dehydration cycles. Thrombolites reflect complex systems due to concurrent interactions among producers (phototrophs), consumers (small invertebrates), mineralization (carbonate precipitation induced by phototrophs) and endolithic dissolution. The microstructures inside thrombolites, in conjunction with biogeochemical attributes of bulk thrombolites, may provide unambiguous sedimentary biosignatures.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"19 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141518564","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}
Ryan T. Tucker, M. Ryan King, Michael T. Mohr, Ray K. Renaut, James L. Crowley, Jack W. Fekete, Peter J. Makovicky, Lindsay E. Zanno
Current investigations into the Albian–Cenomanian sedimentary record within the Western Interior have identified multiple complex tectono‐sedimentary process–response systems during the ongoing evolution of North America. One key sedimentary succession, the upper Cedar Mountain Formation (Short Canyon Member and Mussentuchit Member), has historically been linked to various regionally and continentally significant tectonic events, including Sevier fold‐and‐thrust deformation. However, the linkage between the Short Canyon Member and active Sevier tectonism has been unclear due to a lack of high‐precision age constraints. To establish temporal context, this study compares maximum depositional ages from detrital zircons recovered from the Short Canyon Member with that of a modified Bayesian age stratigraphic model (top‐down) to infer that the Short Canyon Member was deposited at ca 100 Ma, penecontemporaneous with rejuvenated thrusting across Utah [Pavant (Pahvant), Iron Springs and Nebo thrusts]. These also indicate a short depositional hiatus with the lowermost portion of the overlying Mussentuchit Member. The Short Canyon Member and Mussentuchit Member preserve markedly different sedimentary successions, with the Short Canyon Member interpreted to be composed of para‐autochthonous orogen–transverse (across the Sevier highlands) clastics deposited within a series of stacked distributive fluvial fans. Meanwhile, the muddy paralic Mussentuchit Member was a mix of orogen–transverse (Sevier highlands and Cordilleran Arc) and orogen–parallel basinal sediments and suspension settling fines within the developing collisional foredeep. However, the informally named last chance sandstone (middle sandstone of the Mussentuchit Member) is identified as an orogen–transverse sandy debris flow originating from the Sevier highlands, similar to the underlying Short Canyon Member. During this phase of landscape evolution, the Short Canyon Member – Mussentuchit Member depocentre was a sedimentary conduit system that would fertilize the Western Interior Seaway with ash‐rich sediments. These volcaniclastic contributions, along with penecontemporaneous deposits across the western coastal margin of the Western Interior Seaway, eventually would have lowered oxygen content and resulted in a contributing antecedent trigger for the Cenomanian–Turonian transition Oceanic Anoxic Event 2.
{"title":"Tectono‐sedimentary history of the upper Cedar Mountain Formation, Central Utah, USA","authors":"Ryan T. Tucker, M. Ryan King, Michael T. Mohr, Ray K. Renaut, James L. Crowley, Jack W. Fekete, Peter J. Makovicky, Lindsay E. Zanno","doi":"10.1111/sed.13211","DOIUrl":"https://doi.org/10.1111/sed.13211","url":null,"abstract":"Current investigations into the Albian–Cenomanian sedimentary record within the Western Interior have identified multiple complex tectono‐sedimentary process–response systems during the ongoing evolution of North America. One key sedimentary succession, the upper Cedar Mountain Formation (Short Canyon Member and Mussentuchit Member), has historically been linked to various regionally and continentally significant tectonic events, including Sevier fold‐and‐thrust deformation. However, the linkage between the Short Canyon Member and active Sevier tectonism has been unclear due to a lack of high‐precision age constraints. To establish temporal context, this study compares maximum depositional ages from detrital zircons recovered from the Short Canyon Member with that of a modified Bayesian age stratigraphic model (top‐down) to infer that the Short Canyon Member was deposited at <jats:italic>ca</jats:italic> 100 Ma, penecontemporaneous with rejuvenated thrusting across Utah [Pavant (Pahvant), Iron Springs and Nebo thrusts]. These also indicate a short depositional hiatus with the lowermost portion of the overlying Mussentuchit Member. The Short Canyon Member and Mussentuchit Member preserve markedly different sedimentary successions, with the Short Canyon Member interpreted to be composed of para‐autochthonous orogen–transverse (across the Sevier highlands) clastics deposited within a series of stacked distributive fluvial fans. Meanwhile, the muddy paralic Mussentuchit Member was a mix of orogen–transverse (Sevier highlands and Cordilleran Arc) and orogen–parallel basinal sediments and suspension settling fines within the developing collisional foredeep. However, the informally named last chance sandstone (middle sandstone of the Mussentuchit Member) is identified as an orogen–transverse sandy debris flow originating from the Sevier highlands, similar to the underlying Short Canyon Member. During this phase of landscape evolution, the Short Canyon Member – Mussentuchit Member depocentre was a sedimentary conduit system that would fertilize the Western Interior Seaway with ash‐rich sediments. These volcaniclastic contributions, along with penecontemporaneous deposits across the western coastal margin of the Western Interior Seaway, eventually would have lowered oxygen content and resulted in a contributing antecedent trigger for the Cenomanian–Turonian transition Oceanic Anoxic Event 2.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"23 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141529159","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}
Seok‐Hwi Hong, Woo Hun Ryang, Dong‐Geun Yoo, Alexander R. Simms, Jin Cheul Kim, Gwang‐Soo Lee
Bayhead deltas form at the interface between fluvial and estuarine systems. As such, they are sensitive to processes operating in both the fluvial catchment and the marine realm, including past relative sea‐level changes. The Nakdong valley is a small and confined incised valley containing a bayhead delta that provides a record of fluvial sediment input and accommodation changes. Based on a facies analysis that included 833 sediment textures and 118 optically stimulated luminescence and radiocarbon ages within five cores up to 70 m long, this study reconstructed the development of a fully filled bayhead delta in response to relative sea‐level changes through the early to late Holocene. Sixteen facies are defined and grouped into eight facies associations: alluvial plain; fluvial channel and floodplain; oxidized fluvial channel; tidal flat; tidal bar; central basin and bayhead prodelta; bayhead delta front; and bayhead delta plain. The sequence stratigraphy of the Nakdong valley fill can be divided into three systems tracts: a lowstand systems tract, a transgressive systems tract and a highstand systems tract. Overall sedimentary analyses suggest six depositional stages corresponding to variations between sediment inputs and sea‐level rise of the developing bayhead delta in the Nakdong valley. The depositional model tracks relative sea‐level rise in the Nakdong valley after 12 ka during the early to late Holocene. These analyses on the Nakdong bayhead delta succession illustrate the balance between sediment inputs and periods of accelerating and decelerating relative sea‐level rise during the Holocene. The architecture of the valley fill also records two abrupt disequilibrium events from 9 to 8 ka and 5 to 3 ka, likely resulting from rapid sea‐level rise during the deglacial outburst flooding of the early Holocene and decreased sediment inputs during regional climatic changes associated with the middle Holocene, respectively.
湾口三角洲形成于河川和河口系统的交界处。因此，它们对河流集水区和海洋领域的运行过程都很敏感，包括过去相对海平面的变化。洛东河谷是一个狭小而封闭的切入河谷，包含一个湾头三角洲，提供了河道沉积物输入和容纳变化的记录。该研究通过对五个长达 70 米的岩芯中的 833 个沉积物纹理和 118 个光激发发光和放射性碳年龄进行剖面分析，重建了一个完全填充的湾头三角洲在全新世早期至晚期随相对海平面变化而发展的过程。研究界定了 16 个地层面，并将其分为 8 个地层组合：冲积平原、河道和冲积平原、氧化河道、潮汐平地、潮间带、中央盆地和湾头前三角洲、湾头三角洲前沿和湾头三角洲平原。洛东河谷充填层的层序地层学可分为三个系统带：低台地系统带、横断系统带和高台地系统带。总体沉积分析表明，有六个沉积阶段与洛东谷发展中湾头三角洲的沉积输入和海平面上升之间的变化相对应。沉积模型追踪了全新世早至晚期 12 ka 之后洛东谷海平面的相对上升。对洛洞湾头三角洲演替的这些分析说明了全新世期间沉积物输入与海平面相对上升加速期和减速期之间的平衡。河谷充填物的结构还记录了 9 至 8 ka 和 5 至 3 ka 两次突然的不平衡事件，这可能分别是由于全新世早期的冰期溃决洪水导致海平面快速上升和全新世中期的区域气候变化导致沉积物输入减少造成的。
{"title":"Bayhead delta succession as a stratigraphic marker of sea‐level changes during the early to late Holocene – the Nakdong valley of south‐eastern Korea","authors":"Seok‐Hwi Hong, Woo Hun Ryang, Dong‐Geun Yoo, Alexander R. Simms, Jin Cheul Kim, Gwang‐Soo Lee","doi":"10.1111/sed.13203","DOIUrl":"https://doi.org/10.1111/sed.13203","url":null,"abstract":"Bayhead deltas form at the interface between fluvial and estuarine systems. As such, they are sensitive to processes operating in both the fluvial catchment and the marine realm, including past relative sea‐level changes. The Nakdong valley is a small and confined incised valley containing a bayhead delta that provides a record of fluvial sediment input and accommodation changes. Based on a facies analysis that included 833 sediment textures and 118 optically stimulated luminescence and radiocarbon ages within five cores up to 70 m long, this study reconstructed the development of a fully filled bayhead delta in response to relative sea‐level changes through the early to late Holocene. Sixteen facies are defined and grouped into eight facies associations: alluvial plain; fluvial channel and floodplain; oxidized fluvial channel; tidal flat; tidal bar; central basin and bayhead prodelta; bayhead delta front; and bayhead delta plain. The sequence stratigraphy of the Nakdong valley fill can be divided into three systems tracts: a lowstand systems tract, a transgressive systems tract and a highstand systems tract. Overall sedimentary analyses suggest six depositional stages corresponding to variations between sediment inputs and sea‐level rise of the developing bayhead delta in the Nakdong valley. The depositional model tracks relative sea‐level rise in the Nakdong valley after 12 ka during the early to late Holocene. These analyses on the Nakdong bayhead delta succession illustrate the balance between sediment inputs and periods of accelerating and decelerating relative sea‐level rise during the Holocene. The architecture of the valley fill also records two abrupt disequilibrium events from 9 to 8 ka and 5 to 3 ka, likely resulting from rapid sea‐level rise during the deglacial outburst flooding of the early Holocene and decreased sediment inputs during regional climatic changes associated with the middle Holocene, respectively.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"166 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141188368","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}
Yuming Liu, Ting Wang, Tao Wen, Jianguang Zhang, Bo Liu, Yue Li, Hang Zhang, Xiaoqing Rong, Long Ma, Fei Guo, Xingxing Liu, Youbin Sun
Terrigenous clastic sediments cover a large area of the Earth's surface and provide valuable insights into the Earth's evolution and environmental change. Sediment grain-size decomposition has been widely used as an effective approach to inferring changes in sediment sources, transport processes and depositional environments. Several algorithms, such as single sample unmixing, end-member modelling analysis and the universal decomposition model, have been developed for grain-size decomposition. The performance of these algorithms is highly dependent on parameter selections, introducing subjective uncertainty. This uncertainty could undermine the reliability of decomposition results, limit the application of grain-size decomposition techniques and reduce comparability across different studies. To mitigate the methodological uncertainty, a novel deep learning-based framework for grain-size decomposition of terrigenous clastic sediments is proposed. First, an improved universal decomposition model is used to analyse the collected grain-size data, in order to provide training sets for the end-to-end decomposers. To meet the data size requirements of supervised learning, generative adversarial networks are also trained for data augmentation. The performance of the new framework is then evaluated using a small-scale dataset (73 393 samples from 18 sites) of three sedimentary types (loess, fluvial and lake delta deposits). The decomposed grain-size results demonstrate high feasibility and great potential of the framework in constructing a robust grain-size decomposition model. Finally, it is proposed that future grain-size research should aim to establish guidelines for grain-size data sharing and produce a big grain-size database for deep learning.
{"title":"Deep learning-based grain-size decomposition model: A feasible solution for dealing with methodological uncertainty","authors":"Yuming Liu, Ting Wang, Tao Wen, Jianguang Zhang, Bo Liu, Yue Li, Hang Zhang, Xiaoqing Rong, Long Ma, Fei Guo, Xingxing Liu, Youbin Sun","doi":"10.1111/sed.13195","DOIUrl":"https://doi.org/10.1111/sed.13195","url":null,"abstract":"Terrigenous clastic sediments cover a large area of the Earth's surface and provide valuable insights into the Earth's evolution and environmental change. Sediment grain-size decomposition has been widely used as an effective approach to inferring changes in sediment sources, transport processes and depositional environments. Several algorithms, such as single sample unmixing, end-member modelling analysis and the universal decomposition model, have been developed for grain-size decomposition. The performance of these algorithms is highly dependent on parameter selections, introducing subjective uncertainty. This uncertainty could undermine the reliability of decomposition results, limit the application of grain-size decomposition techniques and reduce comparability across different studies. To mitigate the methodological uncertainty, a novel deep learning-based framework for grain-size decomposition of terrigenous clastic sediments is proposed. First, an improved universal decomposition model is used to analyse the collected grain-size data, in order to provide training sets for the end-to-end decomposers. To meet the data size requirements of supervised learning, generative adversarial networks are also trained for data augmentation. The performance of the new framework is then evaluated using a small-scale dataset (73 393 samples from 18 sites) of three sedimentary types (loess, fluvial and lake delta deposits). The decomposed grain-size results demonstrate high feasibility and great potential of the framework in constructing a robust grain-size decomposition model. Finally, it is proposed that future grain-size research should aim to establish guidelines for grain-size data sharing and produce a big grain-size database for deep learning.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"2 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140601567","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}
Edoardo Perri, Mario Borrelli, Ulrich Heimhofer, Bruno Umbro, Pierluigi Santagati, Emilia Le Pera
The Pliocene cold-seep carbonate of the Crotone Basin (South Italy) represents a key site for dimension, outcropping exposure and quality. These deposits form a large carbonate (calcite) body (350 m long, 100 m wide and 40 m thick), and are characterized by a conduit facies made of authigenic calcite interpreted as previously active gas/fluid escape pipes and by a pavement facies, depicted as the surrounding early calcite-cemented bioclastic and siliciclastic sediments. Pavement facies are commonly colonized by chemosymbiotic and non-chemosymbiotic macrofauna (Lucinid and Solemyid bivalves, gastropods and serpulids). The conduit microfacies is characterized by the inward accretion of dark micritic laminae alternating with whitish sparitic layers. The micritic laminae show a microbial peloidal to dendrolitic fabric, which commonly incorporates planktonic foraminifera and coprolites, whereas the crystalline layers consist of microsparitic and sparitic crusts of prismatic zoned calcite crystals. The pavement facies shows more variability, because it is typified by laminated microbial boundstones, chemosymbiotic–bivalves packstone, foraminiferal packstone/wackestone and hybrid arenites. The stratigraphic constraint coupled with the foraminiferal assemblage (planktonic taxa) suggest a deep-water setting occasionally affected by siliciclastic sedimentary flows. The pavement facies also shows common brecciation features, suggesting the establishment of post-depositional overpressure conditions due to the early cementation of the conduits, which triggered localized rock failure. Stable isotope analysis of the different facies reveals overall negative δ13C values (−6.8 to −37.4‰ Vienna PeeDee Belemnite), indicating the presence of a complex mixture of methane with other hydrocarbons consumed microbially via anaerobic oxidation of methane; whereas δ18O is relatively positive (0.0 to 3.4‰ Vienna PeeDee Belemnite) suggesting the possible dehydration of clay minerals and/or destabilization of gas hydrates. This study, besides helping in the definition of the migration pathways and modality of accumulation of hydrocarbon-rich fluids, can also help in building more and more realistic models for the complex genesis of cold-seep carbonates.
{"title":"Microbial dominated Ca-carbonates in a giant Pliocene cold-seep system (Crotone Basin – South Italy)","authors":"Edoardo Perri, Mario Borrelli, Ulrich Heimhofer, Bruno Umbro, Pierluigi Santagati, Emilia Le Pera","doi":"10.1111/sed.13192","DOIUrl":"https://doi.org/10.1111/sed.13192","url":null,"abstract":"The Pliocene cold-seep carbonate of the Crotone Basin (South Italy) represents a key site for dimension, outcropping exposure and quality. These deposits form a large carbonate (calcite) body (350 m long, 100 m wide and 40 m thick), and are characterized by a conduit facies made of authigenic calcite interpreted as previously active gas/fluid escape pipes and by a pavement facies, depicted as the surrounding early calcite-cemented bioclastic and siliciclastic sediments. Pavement facies are commonly colonized by chemosymbiotic and non-chemosymbiotic macrofauna (Lucinid and Solemyid bivalves, gastropods and serpulids). The conduit microfacies is characterized by the inward accretion of dark micritic laminae alternating with whitish sparitic layers. The micritic laminae show a microbial peloidal to dendrolitic fabric, which commonly incorporates planktonic foraminifera and coprolites, whereas the crystalline layers consist of microsparitic and sparitic crusts of prismatic zoned calcite crystals. The pavement facies shows more variability, because it is typified by laminated microbial boundstones, chemosymbiotic–bivalves packstone, foraminiferal packstone/wackestone and hybrid arenites. The stratigraphic constraint coupled with the foraminiferal assemblage (planktonic taxa) suggest a deep-water setting occasionally affected by siliciclastic sedimentary flows. The pavement facies also shows common brecciation features, suggesting the establishment of post-depositional overpressure conditions due to the early cementation of the conduits, which triggered localized rock failure. Stable isotope analysis of the different facies reveals overall negative δ<sup>13</sup>C values (−6.8 to −37.4‰ Vienna PeeDee Belemnite), indicating the presence of a complex mixture of methane with other hydrocarbons consumed microbially via anaerobic oxidation of methane; whereas δ<sup>18</sup>O is relatively positive (0.0 to 3.4‰ Vienna PeeDee Belemnite) suggesting the possible dehydration of clay minerals and/or destabilization of gas hydrates. This study, besides helping in the definition of the migration pathways and modality of accumulation of hydrocarbon-rich fluids, can also help in building more and more realistic models for the complex genesis of cold-seep carbonates.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"25 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140182344","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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