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":null,"pages":null},"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":null,"pages":null},"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}
Song Zhao, Katharine M. Grant, Bradley N. Opdyke, Ulrike Troitzsch, Ian S. Williams
Planktonic foraminiferal shells are widely used to investigate past oceanographic and climatic variations via their trace elements and stable isotopes. However, these geochemical methods may be compromised by the presence of diagenetic high‐Mg calcite. In this study, dolomite crystals are observed in planktonic foraminifera from International Ocean Discovery Program Site U1464 sediments on the Australian Northwest shelf, a shallow marine environment (<300 m). This study investigates the formation of the dolomite using new scanning electron microscopy, X‐ray diffraction, stable isotope (carbon and oxygen), Mg/Ca and rare earth element data, combined with shipboard geochemistry and available literature. This study finds that foraminiferal dolomite formation was probably associated with early diagenesis, microbial and ageing processes. Two potential diagenetic processes (seafloor diagenesis and post‐depositional diagenesis) are proposed, and both indicate that the favourable redox condition of dolomite formation is low oxygen, which may activate methanogenic catalysis to facilitate dolomite formation. It is postulated that high‐Mg calcite may be the precursor of foraminiferal dolomite in this case, and that dissolution–precipitation may be the ageing process of dolomite formation. In contrast to deeper, more normal pelagic environments, this study shows that the marine environment can facilitate dolomite precipitation by higher fluxes of organic matter to the seafloor.
{"title":"Diagenetic dolomite in planktonic foraminifera on the Australian Northwest Shelf","authors":"Song Zhao, Katharine M. Grant, Bradley N. Opdyke, Ulrike Troitzsch, Ian S. Williams","doi":"10.1111/sed.13191","DOIUrl":"https://doi.org/10.1111/sed.13191","url":null,"abstract":"Planktonic foraminiferal shells are widely used to investigate past oceanographic and climatic variations via their trace elements and stable isotopes. However, these geochemical methods may be compromised by the presence of diagenetic high‐Mg calcite. In this study, dolomite crystals are observed in planktonic foraminifera from International Ocean Discovery Program Site U1464 sediments on the Australian Northwest shelf, a shallow marine environment (<300 m). This study investigates the formation of the dolomite using new scanning electron microscopy, X‐ray diffraction, stable isotope (carbon and oxygen), Mg/Ca and rare earth element data, combined with shipboard geochemistry and available literature. This study finds that foraminiferal dolomite formation was probably associated with early diagenesis, microbial and ageing processes. Two potential diagenetic processes (seafloor diagenesis and post‐depositional diagenesis) are proposed, and both indicate that the favourable redox condition of dolomite formation is low oxygen, which may activate methanogenic catalysis to facilitate dolomite formation. It is postulated that high‐Mg calcite may be the precursor of foraminiferal dolomite in this case, and that dissolution–precipitation may be the ageing process of dolomite formation. In contrast to deeper, more normal pelagic environments, this study shows that the marine environment can facilitate dolomite precipitation by higher fluxes of organic matter to the seafloor.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140148324","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}
Renato P. Almeida, Cristiano P. Galeazzi, Jim Best, Marco Ianniruberto, Ariel H. Do Prado, Liliane Janikian, Carlos E. M. Mazoca, Larissa N. Tamura, Andrew Nicholas
Large rivers are characterized by large water discharges, high suspended sediment fluxes and low slope, and typically display multiple channels that are separated by large complex bars. The most common channel style found in these rivers is characterized by the alternating presence of single and multiple channel threads. Mid‐channel compound bars separate a main deeper channel from shallower secondary channels, leading to low‐order braiding and low to moderate sinuosity. Despite the importance of this type of river for global terrestrial sediment transport and the interpretation of ancient fluvial successions, integrated depositional models for large multi‐channel rivers are still not fully developed. This paper interprets the channel morphodynamics and depositional architecture of such large rivers by investigating the distinctive features of their laterally‐accreting mid‐channel bars in the Solimões–Amazonas River. This is achieved by examination of temporal series of satellite images, quantification of bedforms using multibeam echosounding surveys, analysis of shallow seismic and ground penetrating radar surveys of selected areas, and on‐site field observations and sample collections. Such mid‐channel bars produce directional variability in planform scroll bar accretion of up to 180°. As these bars – and their associated channels – evolve, they become progressively shallower, due to the bifurcation of the two channels and the resultant partitioning of discharge that leads to a gradual reduction in transport capacity within the outer channel. The preserved successions of this process in the alluvial plain are characterized by fining‐upward trends, with larger cross‐strata sets at mid‐depths and internal erosional surfaces marking distinct cycles of bar development with potentially differing palaeocurrent trends. The new depositional models proposed for these mid‐channel bars and channels constitute a basis for the recognition of large multi‐channel river deposits in the ancient rock record.
{"title":"Morphodynamics and depositional architecture of mid‐channel bars in large Amazonian rivers","authors":"Renato P. Almeida, Cristiano P. Galeazzi, Jim Best, Marco Ianniruberto, Ariel H. Do Prado, Liliane Janikian, Carlos E. M. Mazoca, Larissa N. Tamura, Andrew Nicholas","doi":"10.1111/sed.13188","DOIUrl":"https://doi.org/10.1111/sed.13188","url":null,"abstract":"Large rivers are characterized by large water discharges, high suspended sediment fluxes and low slope, and typically display multiple channels that are separated by large complex bars. The most common channel style found in these rivers is characterized by the alternating presence of single and multiple channel threads. Mid‐channel compound bars separate a main deeper channel from shallower secondary channels, leading to low‐order braiding and low to moderate sinuosity. Despite the importance of this type of river for global terrestrial sediment transport and the interpretation of ancient fluvial successions, integrated depositional models for large multi‐channel rivers are still not fully developed. This paper interprets the channel morphodynamics and depositional architecture of such large rivers by investigating the distinctive features of their laterally‐accreting mid‐channel bars in the Solimões–Amazonas River. This is achieved by examination of temporal series of satellite images, quantification of bedforms using multibeam echosounding surveys, analysis of shallow seismic and ground penetrating radar surveys of selected areas, and on‐site field observations and sample collections. Such mid‐channel bars produce directional variability in planform scroll bar accretion of up to 180°. As these bars – and their associated channels – evolve, they become progressively shallower, due to the bifurcation of the two channels and the resultant partitioning of discharge that leads to a gradual reduction in transport capacity within the outer channel. The preserved successions of this process in the alluvial plain are characterized by fining‐upward trends, with larger cross‐strata sets at mid‐depths and internal erosional surfaces marking distinct cycles of bar development with potentially differing palaeocurrent trends. The new depositional models proposed for these mid‐channel bars and channels constitute a basis for the recognition of large multi‐channel river deposits in the ancient rock record.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140127315","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}
Clément G. L. Pollier, Alejandro N. Guerrero, Jorge Rabassa, Daniel Ariztegui
Microbialites provide geological evidence into Earth's early ecosystems, recording long‐standing interactions between co‐evolving life and the environment. Yet, after more than 100 years of research, the complex interplay between environmental and biological forces involved in microbialite growth is still debated. Laguna de Los Cisnes, located in Chilean Tierra del Fuego, Patagonia, provides a unique opportunity to study these interactions. This lake, which became ice‐free around 10 000 years ago, features carbonate microbialites developed by algal–microbial communities. Macroscopically, the organo‐sedimentary deposits exhibit a consistent primary crater‐like architecture, showcasing macrostructural variations such as dish‐shaped, hemispherical, columnar and lenticular morphologies. This study explores the environmental and biological factors shaping microbialite macrostructure by analysing the distribution of dominant morphotypes across the basin. Concurrently, it examines the internal mesostructure and microstructure of microbialites in association with prevailing algal–microbial communities. The incremental development of these communities contributes to the distinct crater‐like morphology observed in microbialites from Laguna de Los Cisnes. The mineral encrustation of the green alga Percursaria percursa emerges as a primary driver of lithification, evidenced by the preservation of microfossils within the microstructure of the microbialites. Simultaneously, physical environmental factors, including waves, Langmuir cells and accommodation space influence the location of the algal–microbial carbonate factory, determining the spatial distribution and temporal succession of different crater architecture variants. Laguna de Los Cisnes, hosting well‐preserved subfossil outcrops and living microbialites, serves as a remarkable living laboratory for understanding microbialite morphogenesis. This study contributes to a novel model that captures the fundamental role of algal–microbial communities in determining the primary macrostructural architecture of microbialites before environmental factors come into play, merely reshaping this architecture into different morphotypes.
微生物岩提供了地球早期生态系统的地质证据，记录了共同进化的生命与环境之间长期存在的相互作用。然而，经过 100 多年的研究，关于微生物岩生长所涉及的环境和生物力量之间复杂的相互作用仍存在争议。位于智利巴塔哥尼亚火地岛的洛斯西内斯湖（Laguna de Los Cisnes）为研究这些相互作用提供了一个独特的机会。该湖大约在 1 万年前开始结冰，湖中的碳酸盐微生物岩是由藻类微生物群落形成的。从宏观上看，有机沉积物呈现出一致的原生火山口状结构，并呈现出盘状、半球状、柱状和透镜状等宏观结构变化。本研究通过分析整个盆地的主要形态分布，探讨了形成微生物岩宏观结构的环境和生物因素。同时，研究还将微生物岩的内部中观结构和微观结构与当时的藻类微生物群落联系起来。这些群落的渐进式发展造就了在洛斯西斯内湖微生物岩中观察到的独特的火山口状形态。绿藻 Percursaria percursa 的矿物包壳是岩化的主要驱动力，微生物岩微结构中保存的微化石就是证明。同时，物理环境因素，包括波浪、朗缪尔细胞和容纳空间影响着藻类微生物碳酸盐工厂的位置，决定着不同火山口结构变体的空间分布和时间演替。洛斯西内斯湖（Laguna de Los Cisnes）拥有保存完好的亚化石露头和活的微生物岩，是了解微生物岩形态发生的重要活实验室。这项研究提供了一个新的模型，该模型捕捉到了藻类-微生物群落在决定微生物岩的主要宏观结构构造方面的基本作用，然后环境因素才发挥作用，将这种构造重塑为不同的形态。
{"title":"The hidden biotic face of microbialite morphogenesis – a case study from Laguna de Los Cisnes, southernmost Patagonia (Chile)","authors":"Clément G. L. Pollier, Alejandro N. Guerrero, Jorge Rabassa, Daniel Ariztegui","doi":"10.1111/sed.13189","DOIUrl":"https://doi.org/10.1111/sed.13189","url":null,"abstract":"Microbialites provide geological evidence into Earth's early ecosystems, recording long‐standing interactions between co‐evolving life and the environment. Yet, after more than 100 years of research, the complex interplay between environmental and biological forces involved in microbialite growth is still debated. Laguna de Los Cisnes, located in Chilean Tierra del Fuego, Patagonia, provides a unique opportunity to study these interactions. This lake, which became ice‐free around 10 000 years ago, features carbonate microbialites developed by algal–microbial communities. Macroscopically, the organo‐sedimentary deposits exhibit a consistent primary crater‐like architecture, showcasing macrostructural variations such as dish‐shaped, hemispherical, columnar and lenticular morphologies. This study explores the environmental and biological factors shaping microbialite macrostructure by analysing the distribution of dominant morphotypes across the basin. Concurrently, it examines the internal mesostructure and microstructure of microbialites in association with prevailing algal–microbial communities. The incremental development of these communities contributes to the distinct crater‐like morphology observed in microbialites from Laguna de Los Cisnes. The mineral encrustation of the green alga <jats:italic>Percursaria percursa</jats:italic> emerges as a primary driver of lithification, evidenced by the preservation of microfossils within the microstructure of the microbialites. Simultaneously, physical environmental factors, including waves, Langmuir cells and accommodation space influence the location of the algal–microbial carbonate factory, determining the spatial distribution and temporal succession of different crater architecture variants. Laguna de Los Cisnes, hosting well‐preserved subfossil outcrops and living microbialites, serves as a remarkable living laboratory for understanding microbialite morphogenesis. This study contributes to a novel model that captures the fundamental role of algal–microbial communities in determining the primary macrostructural architecture of microbialites before environmental factors come into play, merely reshaping this architecture into different morphotypes.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140116803","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}
Min Ren, Brian Jones, Xiaomin Nie, Xin Lin, Chuang Meng
Chemosynthetic microorganisms facilitate microbialite development in many caves throughout the world. In Youqin Cave and Tian'e Cave, located in the Carboniferous–Triassic carbonates on the South China Block, five Quaternary speleothems (stalagmite, stalactite and cave pearl) that are 2.3 to 11.0 cm long were examined for their petrographic, geochemical and microbiological features to reveal how chemotrophs contribute to microbialite growth. In the speleothems, millimetre‐sized stromatolites, thrombolites and calcified microbial mats are characterized by alternating light, calcitic microlaminae and dark, clay and organic‐rich calcite microlaminae. Filamentous (reticulate, smooth, nodular and helical), coccoid and bacilliform microbes, originally carried into the caves from surface soils, are more common in the dark microlaminae/clots than in the light microlaminae. 16S rRNA gene sequencing shows that the biotas in the microbialites are dominated by chemoorganotrophic heterotrophic bacteria, including primarily Sphingomonas, Crossiella and Acinetobacter, and rare Archaea. Diverse metabolic pathways of these prokaryotes, including ureolysis, denitrification and nitrite ammonification, contributed to increases in localized pH and/or dissolved inorganic carbon in these microenvironments, prompting carbonate precipitation. Development of the cave microbialites was probably controlled by the evolution of the cave microbial community as environmental conditions changed. Microbialite growth was probably mediated by the microorganisms that flourished on the speleothem surfaces during periods of low drip water rates and slow calcite precipitation. The change from microstromatolites to microthrombolites was probably linked to a decrease in cell populations in the microbial communities. These cave microbialites provide clear insights regarding the biogenicity and growth mechanisms of chemosynthetic microbialites. Given their association with chemolithotrophic activities that can date back to the Meso‐Archean, cave microbialites provide insights into the biogenicity and growth mechanisms of chemosynthesis‐based microbialites throughout geological history.
{"title":"Carbonate microbialites and chemotrophic microbes: Insights from caves from south‐east China","authors":"Min Ren, Brian Jones, Xiaomin Nie, Xin Lin, Chuang Meng","doi":"10.1111/sed.13185","DOIUrl":"https://doi.org/10.1111/sed.13185","url":null,"abstract":"Chemosynthetic microorganisms facilitate microbialite development in many caves throughout the world. In Youqin Cave and Tian'e Cave, located in the Carboniferous–Triassic carbonates on the South China Block, five Quaternary speleothems (stalagmite, stalactite and cave pearl) that are 2.3 to 11.0 cm long were examined for their petrographic, geochemical and microbiological features to reveal how chemotrophs contribute to microbialite growth. In the speleothems, millimetre‐sized stromatolites, thrombolites and calcified microbial mats are characterized by alternating light, calcitic microlaminae and dark, clay and organic‐rich calcite microlaminae. Filamentous (reticulate, smooth, nodular and helical), coccoid and bacilliform microbes, originally carried into the caves from surface soils, are more common in the dark microlaminae/clots than in the light microlaminae. 16S rRNA gene sequencing shows that the biotas in the microbialites are dominated by chemoorganotrophic heterotrophic bacteria, including primarily <jats:italic>Sphingomonas</jats:italic>, <jats:italic>Crossiella</jats:italic> and <jats:italic>Acinetobacter</jats:italic>, and rare Archaea. Diverse metabolic pathways of these prokaryotes, including ureolysis, denitrification and nitrite ammonification, contributed to increases in localized pH and/or dissolved inorganic carbon in these microenvironments, prompting carbonate precipitation. Development of the cave microbialites was probably controlled by the evolution of the cave microbial community as environmental conditions changed. Microbialite growth was probably mediated by the microorganisms that flourished on the speleothem surfaces during periods of low drip water rates and slow calcite precipitation. The change from microstromatolites to microthrombolites was probably linked to a decrease in cell populations in the microbial communities. These cave microbialites provide clear insights regarding the biogenicity and growth mechanisms of chemosynthetic microbialites. Given their association with chemolithotrophic activities that can date back to the Meso‐Archean, cave microbialites provide insights into the biogenicity and growth mechanisms of chemosynthesis‐based microbialites throughout geological history.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140001355","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}
Ailton S. Brito, Afonso C. R. Nogueira, Renan F. Dos Santos, Rômulo S. Angélica, René Rodrigues
Global climatic and palaeogeographical changes generated a siliciclastic–carbonate system with high organic matter accumulations in a shallow sea during the lower Permian in Western Gondwana. The 60 m thick mixed siliciclastic–carbonate succession (Irati Formation and the base of the Serra Alta Formation) from the Paraná Basin represents a singular record of the interplay between carbonate production and siliciclastic input, providing a window of opportunity to integrate large‐scale depositional architecture with facies and geochemical analyses. The detailed study of cores supported by outcrop columnar sections revealed a siliciclastic‐dominated, retrogradational to aggradational facies, and a carbonate‐dominated, mixed aggradational to progradational facies composing three depositional sequences that record an outer‐ramp and mid to upper‐ramp. An integrated approach based on the description of facies and microfacies, organic geochemistry and mineralogical composition, indicated high‐frequency palaeoenvironmental changes during the evolution of this restricted basin. Climate changes, resulting in humid and dry phases, produced ideal conditions for high organic matter production and dolomite formation. The high organic matter production (humid phases) in addition to the restricted condition was responsible for the anoxic bottom waters that were widespread due to the low angle and homoclinal platform. Nutrient‐rich freshwater inflows in the anoxic and hypersaline restricted basin created a density‐stratified water column causing low‐salinity surface and anoxic bottom water, which allowed planktonic life, typical of lakes, such Botryococcus braunii, to flourish in the photic zone and sulphur bacteria to populate below the chemocline. Microbial activity induced primary dolomite precipitation (dry phases) and widespread formation of synsedimentary dolostone. Freshwater inflow and marine incursions are reflected in the organic matter accumulation (kerogen types I and II, respectively), generating bituminous shale with high total organic carbon (5 to 27 wt.%).
全球气候和古地理的变化在冈瓦纳西部二叠纪下统的浅海中产生了有机质积累较多的硅质碎屑岩-碳酸盐岩系统。巴拉那盆地厚 60 米的硅质碎屑岩-碳酸盐岩混合演替（Irati Formation 和 Serra Alta Formation 基底）是碳酸盐岩生成与硅质碎屑岩输入之间相互作用的独特记录，为将大规模沉积结构与岩相和地球化学分析结合起来提供了机会之窗。通过对岩心进行详细研究，并辅以露头柱状切片，发现了一个以硅质岩为主、从逆变到渐变的构造面，以及一个以碳酸盐为主、从渐变到顺变的混合构造面，这三个构造面组成了三个沉积序列，分别记录了外斜、中斜和上斜。通过对岩相和微岩相、有机地球化学和矿物成分进行综合描述，表明在这一狭长盆地的演化过程中，古环境发生了高频率的变化。气候的变化导致了潮湿和干燥阶段，为有机质的大量生产和白云岩的形成创造了理想的条件。高有机质的产生（潮湿阶段）以及受限的条件是造成缺氧底层水的原因，由于低角度和同向平台，缺氧底层水非常普遍。富含营养物质的淡水流入缺氧和高盐的受限盆地，形成了密度分层的水柱，造成了低盐度的表层水和缺氧的底层水，这使得湖泊中典型的浮游生物（如褐藻）在光照区大量繁殖，硫细菌在化学跃层以下大量繁殖。微生物活动促使原生白云石沉淀（干燥阶段），并广泛形成合成白云石。淡水流入和海洋入侵反映在有机质的积累上（分别为 I 型和 II 型角质），产生了总有机碳含量较高（5-27 wt.%）的沥青质页岩。
{"title":"High‐frequency palaeoenvironmental changes in the mixed siliciclastic–carbonate sedimentary system from a lower Permian restricted basin (West Gondwana, southern Brazil)","authors":"Ailton S. Brito, Afonso C. R. Nogueira, Renan F. Dos Santos, Rômulo S. Angélica, René Rodrigues","doi":"10.1111/sed.13184","DOIUrl":"https://doi.org/10.1111/sed.13184","url":null,"abstract":"Global climatic and palaeogeographical changes generated a siliciclastic–carbonate system with high organic matter accumulations in a shallow sea during the lower Permian in Western Gondwana. The 60 m thick mixed siliciclastic–carbonate succession (Irati Formation and the base of the Serra Alta Formation) from the Paraná Basin represents a singular record of the interplay between carbonate production and siliciclastic input, providing a window of opportunity to integrate large‐scale depositional architecture with facies and geochemical analyses. The detailed study of cores supported by outcrop columnar sections revealed a siliciclastic‐dominated, retrogradational to aggradational facies, and a carbonate‐dominated, mixed aggradational to progradational facies composing three depositional sequences that record an outer‐ramp and mid to upper‐ramp. An integrated approach based on the description of facies and microfacies, organic geochemistry and mineralogical composition, indicated high‐frequency palaeoenvironmental changes during the evolution of this restricted basin. Climate changes, resulting in humid and dry phases, produced ideal conditions for high organic matter production and dolomite formation. The high organic matter production (humid phases) in addition to the restricted condition was responsible for the anoxic bottom waters that were widespread due to the low angle and homoclinal platform. Nutrient‐rich freshwater inflows in the anoxic and hypersaline restricted basin created a density‐stratified water column causing low‐salinity surface and anoxic bottom water, which allowed planktonic life, typical of lakes, such <jats:italic>Botryococcus braunii</jats:italic>, to flourish in the photic zone and sulphur bacteria to populate below the chemocline. Microbial activity induced primary dolomite precipitation (dry phases) and widespread formation of synsedimentary dolostone. Freshwater inflow and marine incursions are reflected in the organic matter accumulation (kerogen types I and II, respectively), generating bituminous shale with high total organic carbon (5 to 27 wt.%).","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139947626","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}
Lisa Boterman, Jasper Candel, Bart Makaske, Jakob Wallinga
Channel deposits from meandering rivers have proven to be far more complex than the well-known lithofacies model consisting of coarse-grained channel, gravelly channel-lag and fine-grained overbank deposits. Sharp bends in rivers are subject to different hydraulic processes than bends with lower curvatures, enabling erosion of inner banks and deposition of fine-grained sediments in the outer bend, resulting in downstream migration of river bends. This phenomenon is known as counterpoint deposition, forming counterpoint bars. This research investigates whether scroll bars associated with a sharp bend in the Lower Rhine River, The Netherlands, are such a counterpoint-bar deposit. A counterpoint bar is expected based on: (i) the surface morphology of the scroll bar; (ii) the confinement of the river course by an ice-pushed ridge resulting in a sharp bend; and (iii) the archaeological context of successive Roman settlements atop the ice-pushed ridge, potentially moving downstream with the migrating river bend. This hypothesis is tested through detailed borehole descriptions combined with optically stimulated luminescence dating, the latter being a novel approach to identifying counterpoint deposits. The deposits consist of clays and sandy clays with fine sand laminations, and sporadic larger sand bodies. Further upstream these deposits grade into channel deposits dominated by coarser sands with gravels. These lithologies are explained using earlier proposed mechanisms for counterpoint formation; substrata match those described in previously studied counterpoint deposits and their point bar counterparts. Optically stimulated luminescence dates indicate that the Lower Rhine River bend migrated downstream, confirming counterpoint deposition. A migration rate of 1.93 m/year was established through weighted linear regression. This study demonstrates the potential of optically stimulated luminescence dating to investigate counterpoint bar presence. The identified counterpoint bars and associated bend migration provide insight into meandering river dynamics that is crucial for river management and in aiding river restoration and rewilding initiatives.
{"title":"Late-Holocene counterpoint deposition in the Lower Rhine River","authors":"Lisa Boterman, Jasper Candel, Bart Makaske, Jakob Wallinga","doi":"10.1111/sed.13180","DOIUrl":"https://doi.org/10.1111/sed.13180","url":null,"abstract":"Channel deposits from meandering rivers have proven to be far more complex than the well-known lithofacies model consisting of coarse-grained channel, gravelly channel-lag and fine-grained overbank deposits. Sharp bends in rivers are subject to different hydraulic processes than bends with lower curvatures, enabling erosion of inner banks and deposition of fine-grained sediments in the outer bend, resulting in downstream migration of river bends. This phenomenon is known as counterpoint deposition, forming counterpoint bars. This research investigates whether scroll bars associated with a sharp bend in the Lower Rhine River, The Netherlands, are such a counterpoint-bar deposit. A counterpoint bar is expected based on: (i) the surface morphology of the scroll bar; (ii) the confinement of the river course by an ice-pushed ridge resulting in a sharp bend; and (iii) the archaeological context of successive Roman settlements atop the ice-pushed ridge, potentially moving downstream with the migrating river bend. This hypothesis is tested through detailed borehole descriptions combined with optically stimulated luminescence dating, the latter being a novel approach to identifying counterpoint deposits. The deposits consist of clays and sandy clays with fine sand laminations, and sporadic larger sand bodies. Further upstream these deposits grade into channel deposits dominated by coarser sands with gravels. These lithologies are explained using earlier proposed mechanisms for counterpoint formation; substrata match those described in previously studied counterpoint deposits and their point bar counterparts. Optically stimulated luminescence dates indicate that the Lower Rhine River bend migrated downstream, confirming counterpoint deposition. A migration rate of 1.93 m/year was established through weighted linear regression. This study demonstrates the potential of optically stimulated luminescence dating to investigate counterpoint bar presence. The identified counterpoint bars and associated bend migration provide insight into meandering river dynamics that is crucial for river management and in aiding river restoration and rewilding initiatives.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139917594","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}
Numerical forward modelling and laboratory experiments suggest that autogenic factors in the sediment routing system serve as long-pass filters, preserving only orbital cycles with a period exceeding the compensation timescale, Tc, or thickness in the depth domain exceeding the compensation depth scale, Hc. For a specific orbital cycle with a certain period, this preservation in alluvial strata occurs unless it exhibits a sufficiently large amplitude. This study stratigraphically confirms, for the first time, the long-pass filtering of autogenic dynamics using elemental data from the alluvial–lacustrine Sifangtai and Mingshui formations in the Songliao Basin. Spectral analysis of the Si and Zr series in coarse-grained sediments reveals no cyclic signal with thicknesses below the estimated lower limits of Hc. This implies that the spatial storage threshold for orbital cycles in proxies of the coarse-grained sediment component is equal to or less than Hc. However, cyclic signals of obliquity and precession with smaller thicknesses are identified in Ti, Fe and Al enriched in the fine-grained sediment components of the stratigraphy. Notably, previously reported proxies preserving high-frequency orbital cycles are derived from fine-grained sediment components, differing from the sedimentation rate series used in the reported experimental studies. Therefore, the authors hypothesize a grain-size component-dependent storage threshold, suggesting that the storage threshold of orbital cycles in proxies associated with fine-grained components is lower. This hypothesis arises from the weaker effect of autogenic dynamics on the content of fine-grained sediment components transported to the sampling site by a suspended load compared to coarser components that are subjected to stronger autogenic dynamics within or near channels. The hypothesis and model presented propose a dynamic process elucidating the nuanced roles of autogenic dynamics in preserving orbital cycles. This perspective, considering sediment composition, inspires prioritizing proxies enriched in the fine-grained fraction for identifying allogenic cycles in alluvial strata.
数值模拟和实验室实验表明，沉积溃散系统中的自生因素具有长通滤波器的作用，只保留周期超过补偿时间尺度 Tc 的轨道周期或深度域中厚度超过补偿深度尺度 Hc 的厚度。对于具有一定周期的特定轨道周期，除非其振幅足够大，否则冲积地层中会出现这种保留。本研究利用松辽盆地冲积-湖积地层四方台地层和明水地层的元素数据，首次从地层学角度证实了自生动力学的长通滤波作用。通过对粗粒沉积物中的Si和Zr序列进行光谱分析，发现厚度低于Hc估计下限的沉积物中没有循环信号。这意味着粗粒沉积物部分代用指标中轨道周期的空间储存阈值等于或小于Hc。然而，在地层的细粒沉积物成分中富含的 Ti、Fe 和 Al 中发现了厚度较小的偏斜和前向周期信号。值得注意的是，之前报道的保存高频轨道周期的代用指标均来自细粒沉积成分，与报道的实验研究中使用的沉积速率序列不同。因此，作者提出了一个依赖于粒度成分的存储阈值的假设，认为与细粒度成分相关的代用指标中轨道周期的存储阈值较低。提出这一假设的原因是，与在河道内或河道附近受到较强自生动力学作用的粗粒沉积物相比，悬浮载荷运送到取样地点的细粒沉积物成分含量受到的自生动力学作用较弱。所提出的假设和模型提出了一个动态过程，阐明了自生动力学在保持轨道周期中的微妙作用。从这一角度出发，考虑到沉积物的组成，可以优先使用富含细粒组分的代用指标来识别冲积地层中的自生周期。
{"title":"Grain-size component dependent storage threshold of orbital cycles in alluvial stratigraphy caused by autogenic dynamics","authors":"Daming Yang, Yongjian Huang, Xiang Li, Jianlei Gao, Shitao Yin, Chengshan Wang","doi":"10.1111/sed.13187","DOIUrl":"https://doi.org/10.1111/sed.13187","url":null,"abstract":"Numerical forward modelling and laboratory experiments suggest that autogenic factors in the sediment routing system serve as long-pass filters, preserving only orbital cycles with a period exceeding the compensation timescale, <i>T</i><sub>c</sub>, or thickness in the depth domain exceeding the compensation depth scale, <i>H</i><sub>c</sub>. For a specific orbital cycle with a certain period, this preservation in alluvial strata occurs unless it exhibits a sufficiently large amplitude. This study stratigraphically confirms, for the first time, the long-pass filtering of autogenic dynamics using elemental data from the alluvial–lacustrine Sifangtai and Mingshui formations in the Songliao Basin. Spectral analysis of the Si and Zr series in coarse-grained sediments reveals no cyclic signal with thicknesses below the estimated lower limits of <i>H</i><sub>c</sub>. This implies that the spatial storage threshold for orbital cycles in proxies of the coarse-grained sediment component is equal to or less than <i>H</i><sub>c</sub>. However, cyclic signals of obliquity and precession with smaller thicknesses are identified in Ti, Fe and Al enriched in the fine-grained sediment components of the stratigraphy. Notably, previously reported proxies preserving high-frequency orbital cycles are derived from fine-grained sediment components, differing from the sedimentation rate series used in the reported experimental studies. Therefore, the authors hypothesize a grain-size component-dependent storage threshold, suggesting that the storage threshold of orbital cycles in proxies associated with fine-grained components is lower. This hypothesis arises from the weaker effect of autogenic dynamics on the content of fine-grained sediment components transported to the sampling site by a suspended load compared to coarser components that are subjected to stronger autogenic dynamics within or near channels. The hypothesis and model presented propose a dynamic process elucidating the nuanced roles of autogenic dynamics in preserving orbital cycles. This perspective, considering sediment composition, inspires prioritizing proxies enriched in the fine-grained fraction for identifying allogenic cycles in alluvial strata.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139928722","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}
Wei Li, Sebastian Krastel, Tiago M. Alves, Song Jing, Michele Rebesco, Felix Gross, Morelia Urlaub, Aggeliki Georgiopoulou
Mixed turbidite–contourite depositional systems result from interactions between down-slope turbidity currents and along-slope bottom currents, comprising excellent records of past oceanographic currents. Modern and ancient systems have been widely documented along the continental margins of the Atlantic Ocean. Yet, few examples have so far been identified on the North-west African continental margin, limiting understanding of the sedimentary and palaeoceanographic evolution in this area. This work uses two-dimensional seismic reflection profiles to report, for the first time, the presence of three giant sediment mounds beneath the headwall region of the Sahara Slide Complex. The sediment mounds are elongated and separated by two broad canyons, showing a north-west/south-east orientation that is roughly perpendicular to the continental margin. These mounds are 24 to 37 km long and 12 to 17 km wide, reaching a maximum height of ca 1000 m. Numerous slide scarps are observed within and along the flanks of the mounds, hinting at the occurrence of submarine landslides during their development. Based on their geometries, external shapes, internal seismic architecture and stratigraphic stacking patterns, it is proposed that these sediment mounds comprise down-slope elongated mounded drifts formed in a mixed turbidite–contourite system during four evolutionary stages: onset, growth, maintenance and burial. The significance of this work is that it demonstrates the gradual transition from a turbidite system to a full mixed turbidite–contourite system to be associated, in the study area, with the establishment of strong ocean currents along north-west Africa.
{"title":"Origin, evolution and significance of giant buried sediment mounds near the Sahara Slide Complex, North-west African margin","authors":"Wei Li, Sebastian Krastel, Tiago M. Alves, Song Jing, Michele Rebesco, Felix Gross, Morelia Urlaub, Aggeliki Georgiopoulou","doi":"10.1111/sed.13182","DOIUrl":"https://doi.org/10.1111/sed.13182","url":null,"abstract":"Mixed turbidite–contourite depositional systems result from interactions between down-slope turbidity currents and along-slope bottom currents, comprising excellent records of past oceanographic currents. Modern and ancient systems have been widely documented along the continental margins of the Atlantic Ocean. Yet, few examples have so far been identified on the North-west African continental margin, limiting understanding of the sedimentary and palaeoceanographic evolution in this area. This work uses two-dimensional seismic reflection profiles to report, for the first time, the presence of three giant sediment mounds beneath the headwall region of the Sahara Slide Complex. The sediment mounds are elongated and separated by two broad canyons, showing a north-west/south-east orientation that is roughly perpendicular to the continental margin. These mounds are 24 to 37 km long and 12 to 17 km wide, reaching a maximum height of <i>ca</i> 1000 m. Numerous slide scarps are observed within and along the flanks of the mounds, hinting at the occurrence of submarine landslides during their development. Based on their geometries, external shapes, internal seismic architecture and stratigraphic stacking patterns, it is proposed that these sediment mounds comprise down-slope elongated mounded drifts formed in a mixed turbidite–contourite system during four evolutionary stages: onset, growth, maintenance and burial. The significance of this work is that it demonstrates the gradual transition from a turbidite system to a full mixed turbidite–contourite system to be associated, in the study area, with the establishment of strong ocean currents along north-west Africa.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139928592","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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