Carbonate cementation in the Upper Permian sandstones informs the timing and temperature of hydrothermal activity in the south‐western Ordos Basin. This study presents a detailed examination of these hydrothermally influenced carbonate cements, constraining their age, carbonate diagenesis and relationship with regional geodynamic evolution. Sedimentological analyses demonstrate the development of deltaic plain and front sand bodies in the study area, which resulted in interbeds of volcanic matrix‐rich sandstones with matrix‐free sandstones. Petrography and electron microprobe analysis reveal four carbonate mineral growth phases of matrix‐free sandstones in the following sequence; scarce pure siderite, scarce Mg‐rich siderite, abundant blocky calcite and moderately abundant grain‐replacing calcite. The fluid inclusion data show anomalies of homogenization temperature of blocky carbonate cements during early diagenesis, over a wide range of ca 148 to 228°C. In addition, blocky carbonate cements show low δ13C (−5.9 to −13.1‰ Vienna PeeDee Belemnite) and δ18O (clustered tightly from −12.4 to −14.6‰ Vienna PeeDee Belemnite) values, interpreted to result from elevated temperatures during cementation, associated with activation of basement faults and concomitant hydrothermal fluid intrusion triggered by oceanic crust subduction in the south‐west margin of the Ordos Basin. Using in situ calcite U–Pb geochronology, the timing of hydrothermal activity was constrained to ca 247.0 ± 11 to 248.2 ± 4.7 Ma. This work provides a case study for applying intergranular calcite U–Pb dating to determine the absolute timing of fluid flow in sedimentary basins, offering tremendous potential to capture snapshots of various diagenetic evolution stages in sediments. The proposed diagenetic model can also provide new insights and understanding regarding hydrothermally influenced sediments. More importantly, hydrothermal activity may have commenced earlier than previously thought. The North Qinling Orogen uplift and associated Mianlue oceanic crust subduction may have begun at the Permian–Triassic transition with a protracted hydrothermal event in the south‐western Ordos Basin.
{"title":"Hydrothermal activity near the Permian–Triassic transition in the south‐western Ordos Basin, China: Evidence from carbonate cementation in Upper Permian sandstones","authors":"Hang Cui, Shifa Zhu, Yishan Gao, Weiyan Chen","doi":"10.1111/sed.13232","DOIUrl":"https://doi.org/10.1111/sed.13232","url":null,"abstract":"Carbonate cementation in the Upper Permian sandstones informs the timing and temperature of hydrothermal activity in the south‐western Ordos Basin. This study presents a detailed examination of these hydrothermally influenced carbonate cements, constraining their age, carbonate diagenesis and relationship with regional geodynamic evolution. Sedimentological analyses demonstrate the development of deltaic plain and front sand bodies in the study area, which resulted in interbeds of volcanic matrix‐rich sandstones with matrix‐free sandstones. Petrography and electron microprobe analysis reveal four carbonate mineral growth phases of matrix‐free sandstones in the following sequence; scarce pure siderite, scarce Mg‐rich siderite, abundant blocky calcite and moderately abundant grain‐replacing calcite. The fluid inclusion data show anomalies of homogenization temperature of blocky carbonate cements during early diagenesis, over a wide range of <jats:italic>ca</jats:italic> 148 to 228°C. In addition, blocky carbonate cements show low δ<jats:sup>13</jats:sup>C (−5.9 to −13.1‰ Vienna PeeDee Belemnite) and δ<jats:sup>18</jats:sup>O (clustered tightly from −12.4 to −14.6‰ Vienna PeeDee Belemnite) values, interpreted to result from elevated temperatures during cementation, associated with activation of basement faults and concomitant hydrothermal fluid intrusion triggered by oceanic crust subduction in the south‐west margin of the Ordos Basin. Using <jats:italic>in situ</jats:italic> calcite U–Pb geochronology, the timing of hydrothermal activity was constrained to <jats:italic>ca</jats:italic> 247.0 ± 11 to 248.2 ± 4.7 Ma. This work provides a case study for applying intergranular calcite U–Pb dating to determine the absolute timing of fluid flow in sedimentary basins, offering tremendous potential to capture snapshots of various diagenetic evolution stages in sediments. The proposed diagenetic model can also provide new insights and understanding regarding hydrothermally influenced sediments. More importantly, hydrothermal activity may have commenced earlier than previously thought. The North Qinling Orogen uplift and associated Mianlue oceanic crust subduction may have begun at the Permian–Triassic transition with a protracted hydrothermal event in the south‐western Ordos Basin.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"9 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269678","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}
Yi‐Fan Zhang, Mathias Mueller, René Hoffmann, Sylvia Riechelmann, Sumit Chakraborty, Stephen E. Kaczmarek, Christopher Beyer, Adrian Immenhauser
Saddle dolomite is a Ca–Mg carbonate characterized by curved crystal faces, curved cleavage and sweeping extinction under cross‐polarized light. Saddle dolomite and, generally, Ca–Mg carbonates with curved crystal faces, are often assigned to the burial (hydrothermal) realm and serve as proxy archives for hydrogeochemical processes in sedimentary basins and orogens. At present, the physicochemical conditions leading to the formation of these peculiar warped carbonates are unclear, and the mechanisms inducing the curvature of their crystal lattice are debated. This study uses laboratory experiments to assess the factors controlling the formation of carbonates with curved crystal faces as a function of fluid temperature, reactant size, fluid salinity and fluid Mg : Ca. Results show that a range of magnesium calcites with curved surfaces form at elevated temperatures (ca 220°C) from calcium‐rich fluids (Mg : Ca = 0.43) within a wide range of fluid salinities (5 to 40 wt.%). Magnesium calcites that nucleate epitaxially on rhombohedral or saddle dolomite substrates exhibit warped surfaces, while those that nucleate on calcite seeds form flat surfaces. Although the two crystal habits can co‐occur, Mg‐calcites with curved crystal faces (Mg : Ca of 0.35 to 0.40) tend to be more calcium‐rich than those with flat faces (Mg : Ca of 0.58 to 0.74). In experiments with higher fluid temperature (230°C), calcite reactants undergo replacement by dolomite exhibiting planar crystal faces. The results collectively indicate that the formation of Ca–Mg carbonates with warped surfaces is likely related to a combination of geochemical and physical parameters and various threshold limits, as opposed to one specific parameter, for example, elevated fluid temperature, as is commonly reported in the literature. Although most of the present experimental precipitates are disordered magnesian calcites with bent crystal faces, it is reasonable, at the level of a tentative working hypothesis, that these represent precursors of many ancient saddle dolomites commonly found in burial settings.
鞍状白云石是一种钙镁碳酸盐岩，其特征是晶体面弯曲、劈理弯曲以及在交叉偏振光下出现扫射消光。鞍状白云石以及一般具有弯曲晶面的钙镁碳酸盐通常被归入埋藏（热液）领域，并可作为沉积盆地和造山运动中水文地球化学过程的替代档案。目前，导致这些奇特翘曲碳酸盐形成的物理化学条件尚不清楚，而导致其晶格弯曲的机制也存在争议。本研究利用实验室实验评估了控制具有弯曲晶面的碳酸盐形成的因素，这些因素是流体温度、反应物大小、流体盐度和流体镁钙比的函数。结果表明，在较宽的流体盐度范围（5 至 40 wt.%）内，富含钙的流体（镁：钙 = 0.43）在较高温度（约 220°C）下会形成一系列具有弯曲表面的镁方解石。在斜长石或鞍状白云石基质上外延成核的镁方解石表面呈翘曲状，而在方解石种子上成核的镁方解石则表面平坦。虽然这两种晶体习性可以共存，但具有弯曲晶面（Mg : Ca 值为 0.35 至 0.40）的镁方解石往往比具有平坦晶面（Mg : Ca 值为 0.58 至 0.74）的镁方解石富含更多的钙。在流体温度较高（230°C）的实验中，方解石反应物被显示平面晶面的白云石取代。这些结果共同表明，具有翘曲表面的钙镁碳酸盐的形成很可能与地球化学和物理参数的组合以及各种阈值极限有关，而不是像文献中通常报道的那样只与一个特定参数有关，例如流体温度升高。虽然目前的实验沉淀物大多是晶面弯曲的无序菱镁方解石，但在初步工作假设的层面上，这些沉淀物代表了许多在埋藏环境中常见的古鞍白云岩的前身，这是合理的。
{"title":"Towards an improved understanding of Ca–Mg carbonates with nonplanar surfaces: An experimental approach","authors":"Yi‐Fan Zhang, Mathias Mueller, René Hoffmann, Sylvia Riechelmann, Sumit Chakraborty, Stephen E. Kaczmarek, Christopher Beyer, Adrian Immenhauser","doi":"10.1111/sed.13228","DOIUrl":"https://doi.org/10.1111/sed.13228","url":null,"abstract":"Saddle dolomite is a Ca–Mg carbonate characterized by curved crystal faces, curved cleavage and sweeping extinction under cross‐polarized light. Saddle dolomite and, generally, Ca–Mg carbonates with curved crystal faces, are often assigned to the burial (hydrothermal) realm and serve as proxy archives for hydrogeochemical processes in sedimentary basins and orogens. At present, the physicochemical conditions leading to the formation of these peculiar warped carbonates are unclear, and the mechanisms inducing the curvature of their crystal lattice are debated. This study uses laboratory experiments to assess the factors controlling the formation of carbonates with curved crystal faces as a function of fluid temperature, reactant size, fluid salinity and fluid Mg : Ca. Results show that a range of magnesium calcites with curved surfaces form at elevated temperatures (<jats:italic>ca</jats:italic> 220°C) from calcium‐rich fluids (Mg : Ca = 0.43) within a wide range of fluid salinities (5 to 40 wt.%). Magnesium calcites that nucleate epitaxially on rhombohedral or saddle dolomite substrates exhibit warped surfaces, while those that nucleate on calcite seeds form flat surfaces. Although the two crystal habits can co‐occur, Mg‐calcites with curved crystal faces (Mg : Ca of 0.35 to 0.40) tend to be more calcium‐rich than those with flat faces (Mg : Ca of 0.58 to 0.74). In experiments with higher fluid temperature (230°C), calcite reactants undergo replacement by dolomite exhibiting planar crystal faces. The results collectively indicate that the formation of Ca–Mg carbonates with warped surfaces is likely related to a combination of geochemical and physical parameters and various threshold limits, as opposed to one specific parameter, for example, elevated fluid temperature, as is commonly reported in the literature. Although most of the present experimental precipitates are disordered magnesian calcites with bent crystal faces, it is reasonable, at the level of a tentative working hypothesis, that these represent precursors of many ancient saddle dolomites commonly found in burial settings.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"138 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192891","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}
Sruthi P. Sreenivasan, Melinda Kumar Bera, Arpita Samanta
Since diagnostic primary depositional sedimentary structures and depth‐dependent grain‐size trends are rarely preserved, building a comprehensive sequence stratigraphic framework for the vast majority of the Phanerozoic carbonate platform sequences is pending. Among the two most important sequence stratigraphic surfaces, while the subaerial unconformity can be reliably identified by either karst development or the appearance of siliciclastic materials, the demarcation of the maximum flooding surface remains difficult in lithologically uniform shallow marine carbonate sequences. The present study attempts to identify the globally documented maximum flooding surface within the body of the negative carbon isotope excursion of the Palaeocene–Eocene Thermal Maximum recorded in the shallow marine carbonate platform sequences. The results show that, along with the carbonate microfacies, the yttrium to holmium ratio (Y/Ho ratio) of the carbonate fraction reliably records the sea‐level changes. A Y/Ho ratio between 70 and 80 demarcates the stratigraphic position of the maximum sea‐level state (the most open marine condition in the studied interval) and maximum flooding surface in the studied sections. Since the Y/Ho ratios remain relatively stable throughout diagenesis, they can be used for maximum flooding surface identification in shallow marine carbonate platform sequences. The possibility exists that the same method can also be applied to the mixed siliciclastic–carbonate systems.
{"title":"Recognition of a cryptic maximum flooding surface in shallow marine carbonate sequences using geochemical (Y/Ho) proxy data","authors":"Sruthi P. Sreenivasan, Melinda Kumar Bera, Arpita Samanta","doi":"10.1111/sed.13229","DOIUrl":"https://doi.org/10.1111/sed.13229","url":null,"abstract":"Since diagnostic primary depositional sedimentary structures and depth‐dependent grain‐size trends are rarely preserved, building a comprehensive sequence stratigraphic framework for the vast majority of the Phanerozoic carbonate platform sequences is pending. Among the two most important sequence stratigraphic surfaces, while the subaerial unconformity can be reliably identified by either karst development or the appearance of siliciclastic materials, the demarcation of the maximum flooding surface remains difficult in lithologically uniform shallow marine carbonate sequences. The present study attempts to identify the globally documented maximum flooding surface within the body of the negative carbon isotope excursion of the Palaeocene–Eocene Thermal Maximum recorded in the shallow marine carbonate platform sequences. The results show that, along with the carbonate microfacies, the yttrium to holmium ratio (Y/Ho ratio) of the carbonate fraction reliably records the sea‐level changes. A Y/Ho ratio between 70 and 80 demarcates the stratigraphic position of the maximum sea‐level state (the most open marine condition in the studied interval) and maximum flooding surface in the studied sections. Since the Y/Ho ratios remain relatively stable throughout diagenesis, they can be used for maximum flooding surface identification in shallow marine carbonate platform sequences. The possibility exists that the same method can also be applied to the mixed siliciclastic–carbonate systems.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"8 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192894","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}
Minsik Kim, Byongsuk Chun, Elizabeth Chamberlain, Wonsuck Kim
Mud deposition is acknowledged as a significant contributor to delta architecture, yet its role is often oversimplified as a constant parameter in models of delta formation. A better understanding of mud retention on deltas would resolve remaining questions regarding delta growth. This study explores how spatiotemporally varied mud retention facilitates sustained delta growth in defiance of the concept of autoretreat, that is, the idea that shoreline progradation rates decline as a delta grows due to the expansion of subaqueous and subaerial delta surfaces. This research is inspired by prior field observations of the river‐dominated Mississippi Delta, USA, where the shoreline of a ca 6000 to 8000 km2 subdelta prograded at a constant rate for roughly a millennium, despite its expanding delta surface, compaction and sea‐level rise. For this, a laterally averaged one‐dimensional numerical model is leveraged to test hypotheses that enhanced mud retention with time in: (i) the delta bottomset; and (ii) the delta plain (floodplain) supports a constant rate of shoreline progradation in a maturing delta. Results demonstrate that enhanced mud retention in both the bottomset and delta plain facilitates sustained delta growth. Neither component by itself can replicate the case study. Yet, with these two integrated components, the model reproduces the cross‐section and linearly prograding pattern observed in the Mississippi Delta. The findings provide an autogenic mechanism for sustained delta growth and support the importance of mud as a fundamental building block of deltas that should be incorporated in delta‐growth models of engineered river diversions.
{"title":"Enhanced mud retention as an autogenic mechanism for sustained delta growth: Insight from records of the Lafourche subdelta of the Mississippi River","authors":"Minsik Kim, Byongsuk Chun, Elizabeth Chamberlain, Wonsuck Kim","doi":"10.1111/sed.13230","DOIUrl":"https://doi.org/10.1111/sed.13230","url":null,"abstract":"Mud deposition is acknowledged as a significant contributor to delta architecture, yet its role is often oversimplified as a constant parameter in models of delta formation. A better understanding of mud retention on deltas would resolve remaining questions regarding delta growth. This study explores how spatiotemporally varied mud retention facilitates sustained delta growth in defiance of the concept of autoretreat, that is, the idea that shoreline progradation rates decline as a delta grows due to the expansion of subaqueous and subaerial delta surfaces. This research is inspired by prior field observations of the river‐dominated Mississippi Delta, USA, where the shoreline of a <jats:italic>ca</jats:italic> 6000 to 8000 km<jats:sup>2</jats:sup> subdelta prograded at a constant rate for roughly a millennium, despite its expanding delta surface, compaction and sea‐level rise. For this, a laterally averaged one‐dimensional numerical model is leveraged to test hypotheses that enhanced mud retention with time in: (i) the delta bottomset; and (ii) the delta plain (floodplain) supports a constant rate of shoreline progradation in a maturing delta. Results demonstrate that enhanced mud retention in both the bottomset and delta plain facilitates sustained delta growth. Neither component by itself can replicate the case study. Yet, with these two integrated components, the model reproduces the cross‐section and linearly prograding pattern observed in the Mississippi Delta. The findings provide an autogenic mechanism for sustained delta growth and support the importance of mud as a fundamental building block of deltas that should be incorporated in delta‐growth models of engineered river diversions.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"62 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192896","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}
Sonia Campos‐Soto, Bernadette Tessier, Dominique Mouazé, M. Isabel Benito, I. Emma Quijada, Pablo Suarez‐Gonzalez
Despite the valuable palaeoecological and palaeoenvironmental information provided by vertebrate tracks, those made in semi‐liquid sediments have been largely overlooked because they are assumed to be preserved as a mass of disrupted sediment and to have a low preservation potential. Nevertheless, understanding their mechanisms of formation, infilling and preservation is crucial since they could be more abundant in the fossil record than expected or be misinterpreted as other soft‐sediment deformation structures. To solve these aspects, this study analyses consecutive cross‐sections performed along a human track made by a shod foot in semi‐liquid sediments in the upper intertidal flats of the Bay of Mont‐Saint‐Michel (north‐west France) and monitored until its complete burial. These were compared with cross‐sections of tracks made in a flume tank. Cross‐sections reveal that the sediment structures associated with these tracks reflect the mechanism of their formation and infilling, and even the footstep dynamics. These structures comprise: (i) marginal rims that developed at both sides of tracks during foot penetration; (ii) upward deformation structures produced during foot withdrawal; (iii) a syn‐track infilling, which almost entirely fills the tracks during the withdrawal, formed by sediment collapsed from the track walls or by liquefied sediment; (iv) a post‐track infilling that fills the tracks completely during their subsequent flooding. This work demonstrates that these tracks have a high preservation potential in tidal settings, especially if they are made after the peak of a spring tide period, and undergo desiccation and consolidation during neap tides, which prevents their erosion and favours their burial by sediment. The identification of the above‐mentioned structures in fossil counterparts provides useful palaeoenvironmental information, because they allow discriminating these tracks from those made in sediments with less water content and from other soft‐sediment deformation structures (i.e. convolute bedding and balls‐and pillows) with which they share strong resemblances.
{"title":"Formation and preservation of vertebrate tracks in semi‐liquid sediments: Insights from tidal flats and laboratory experiments","authors":"Sonia Campos‐Soto, Bernadette Tessier, Dominique Mouazé, M. Isabel Benito, I. Emma Quijada, Pablo Suarez‐Gonzalez","doi":"10.1111/sed.13224","DOIUrl":"https://doi.org/10.1111/sed.13224","url":null,"abstract":"Despite the valuable palaeoecological and palaeoenvironmental information provided by vertebrate tracks, those made in semi‐liquid sediments have been largely overlooked because they are assumed to be preserved as a mass of disrupted sediment and to have a low preservation potential. Nevertheless, understanding their mechanisms of formation, infilling and preservation is crucial since they could be more abundant in the fossil record than expected or be misinterpreted as other soft‐sediment deformation structures. To solve these aspects, this study analyses consecutive cross‐sections performed along a human track made by a shod foot in semi‐liquid sediments in the upper intertidal flats of the Bay of Mont‐Saint‐Michel (north‐west France) and monitored until its complete burial. These were compared with cross‐sections of tracks made in a flume tank. Cross‐sections reveal that the sediment structures associated with these tracks reflect the mechanism of their formation and infilling, and even the footstep dynamics. These structures comprise: (i) marginal rims that developed at both sides of tracks during foot penetration; (ii) upward deformation structures produced during foot withdrawal; (iii) a <jats:italic>syn‐track infilling</jats:italic>, which almost entirely fills the tracks during the withdrawal, formed by sediment collapsed from the track walls or by liquefied sediment; (iv) a <jats:italic>post‐track infilling</jats:italic> that fills the tracks completely during their subsequent flooding. This work demonstrates that these tracks have a high preservation potential in tidal settings, especially if they are made after the peak of a spring tide period, and undergo desiccation and consolidation during neap tides, which prevents their erosion and favours their burial by sediment. The identification of the above‐mentioned structures in fossil counterparts provides useful palaeoenvironmental information, because they allow discriminating these tracks from those made in sediments with less water content and from other soft‐sediment deformation structures (i.e. convolute bedding and balls‐and pillows) with which they share strong resemblances.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"75 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192921","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}
Renaldo Gastineau, Stéphanie Girardclos, Katrina Kremer, Flavio S. Anselmetti
River regulations have resulted in changes in the hydrology and particle budgets of fluvial systems. Since the 19th century, many rivers have been significantly modified to control flood hazards, to gain land from swamp areas for agricultural purposes, and to stabilize river‐levels and lake‐levels to facilitate navigation. These dramatic changes of the river courses have impacted the sediment budgets and grain‐size dissemination along them as well as the sediment distribution at the delta mouths in the downstream lakes, which could lead to slope instabilities. Deposits of such catastrophic lacustrine mass movements caused by delta collapses have been, for instance, observed in Lake Brienz (Switzerland), where relatively thick (0.5 to 1.3 m) and voluminous (>1 million m3) megaturbidites are stacked in the deep basin witnessing these processes. This study uses sediment cores and seismic data to reconstruct the megaturbidites' history in Lake Brienz. Data reveal that mass‐movement deposits, originating from the Aare Delta, one of the two main inflows, have mean ages of 1853, 1905, 1942 and 1996 ce and that they were unprecedented in, at least, half a millennium. The fact that the numbers of floods and earthquakes have not changed radically over this time period implies that human impact is the most likely explanation for these failure events. Therefore, the recurrent delta collapses are attributed to the focused sediment accumulation at the front of the channelized inflow in the proximal delta region, caused by the modification of the Aare River through its straightening and channelization during the late 19th century. These findings indicate that river regulation can affect delta sedimentation, leading to autocyclic delta collapses. Those collapses, in turn, can potentially generate tsunami waves, representing an additional natural hazard for shoreline communities.
{"title":"Human‐initiated autocyclic delta failures","authors":"Renaldo Gastineau, Stéphanie Girardclos, Katrina Kremer, Flavio S. Anselmetti","doi":"10.1111/sed.13226","DOIUrl":"https://doi.org/10.1111/sed.13226","url":null,"abstract":"River regulations have resulted in changes in the hydrology and particle budgets of fluvial systems. Since the 19th century, many rivers have been significantly modified to control flood hazards, to gain land from swamp areas for agricultural purposes, and to stabilize river‐levels and lake‐levels to facilitate navigation. These dramatic changes of the river courses have impacted the sediment budgets and grain‐size dissemination along them as well as the sediment distribution at the delta mouths in the downstream lakes, which could lead to slope instabilities. Deposits of such catastrophic lacustrine mass movements caused by delta collapses have been, for instance, observed in Lake Brienz (Switzerland), where relatively thick (0.5 to 1.3 m) and voluminous (>1 million m<jats:sup>3</jats:sup>) megaturbidites are stacked in the deep basin witnessing these processes. This study uses sediment cores and seismic data to reconstruct the megaturbidites' history in Lake Brienz. Data reveal that mass‐movement deposits, originating from the Aare Delta, one of the two main inflows, have mean ages of 1853, 1905, 1942 and 1996 <jats:sc>ce</jats:sc> and that they were unprecedented in, at least, half a millennium. The fact that the numbers of floods and earthquakes have not changed radically over this time period implies that human impact is the most likely explanation for these failure events. Therefore, the recurrent delta collapses are attributed to the focused sediment accumulation at the front of the channelized inflow in the proximal delta region, caused by the modification of the Aare River through its straightening and channelization during the late 19th century. These findings indicate that river regulation can affect delta sedimentation, leading to autocyclic delta collapses. Those collapses, in turn, can potentially generate tsunami waves, representing an additional natural hazard for shoreline communities.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"2 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142192897","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}
Fengtao Guo, Peter McCabe, Zhiqiang Feng, Zhongmin Zhang, Weilong Peng
Lake systems are among the largest integrated depositional complexes in the continental realm. Their interplay with tectonics and climate often complicates the interpretation of depositional processes, usually resulting in a complex facies architecture that is challenging to correlate regionally. The Lower to Middle Permian Roseneath–Epsilon–Murteree strata of the Cooper Basin in Australia represent a glacially influenced fluvial–deltaic lake system, which hosts substantial petroleum resources. Despite their potential, the Roseneath–Epsilon–Murteree strata are inadequately understood in terms of regional facies architecture and their palaeogeographical implications. Using a multidisciplinary approach with robust data, including cores, petrology, wireline logs and geochemistry, the sedimentary evolution of the Roseneath–Epsilon–Murteree strata is described within a new basin‐wide sequence stratigraphic framework defined by key surfaces identified from cores and wireline logs. Detailed facies analysis of over 1400 m of cores and wireline logs from nine wells identified twelve lithofacies and eight facies associations, revealing various depositional processes and environments. The Roseneath–Epsilon–Murteree strata are interpreted as having formed in a fluvial–deltaic–lacustrine system influenced by a cold climate. First‐order and second‐order maximum flooding surfaces define a regional sequence stratigraphic framework, subdividing the Roseneath–Epsilon–Murteree strata into four sequence units (SU1, SU2, SU3 and SU4), deposited during four phases (I, II, III and IV). Cyclic stacking patterns observed in both cores and wireline logs reveal two transgressive–regressive cycles. Palaeogeographical maps of the four depositional phases suggest that the Roseneath–Epsilon–Murteree strata were dominated by a lacustrine system with some delta and mire deposits. Rivers primarily drained towards the south/south‐west from the Gidgealpa, Merrimelia, Packsaddle and Innamincka ridges (‘GMI Trend’) as indicated by decreasing sandstone percentages and increasing gross unit isopach maps. The deposition of the Roseneath–Epsilon–Murteree strata was primarily controlled by basin subsidence. Additionally, palaeoclimate trends and extensive glaciation in the Permian played important roles in providing sediments and affecting lake level changes. The lake system recorded by the Roseneath–Epsilon–Murteree strata serves as an analogue for other fluvial–deltaic–lacustrine systems in basins worldwide. A multidisciplinary approach, similar to the one utilized in this study, can help to elucidate their evolution and aid in resource prediction.
{"title":"Depositional environments of complex lake systems – palaeogeographical evolution and main controls: A case study of the Lower to Middle Permian Roseneath–Epsilon–Murteree strata, Cooper Basin, Australia","authors":"Fengtao Guo, Peter McCabe, Zhiqiang Feng, Zhongmin Zhang, Weilong Peng","doi":"10.1111/sed.13223","DOIUrl":"https://doi.org/10.1111/sed.13223","url":null,"abstract":"Lake systems are among the largest integrated depositional complexes in the continental realm. Their interplay with tectonics and climate often complicates the interpretation of depositional processes, usually resulting in a complex facies architecture that is challenging to correlate regionally. The Lower to Middle Permian Roseneath–Epsilon–Murteree strata of the Cooper Basin in Australia represent a glacially influenced fluvial–deltaic lake system, which hosts substantial petroleum resources. Despite their potential, the Roseneath–Epsilon–Murteree strata are inadequately understood in terms of regional facies architecture and their palaeogeographical implications. Using a multidisciplinary approach with robust data, including cores, petrology, wireline logs and geochemistry, the sedimentary evolution of the Roseneath–Epsilon–Murteree strata is described within a new basin‐wide sequence stratigraphic framework defined by key surfaces identified from cores and wireline logs. Detailed facies analysis of over 1400 m of cores and wireline logs from nine wells identified twelve lithofacies and eight facies associations, revealing various depositional processes and environments. The Roseneath–Epsilon–Murteree strata are interpreted as having formed in a fluvial–deltaic–lacustrine system influenced by a cold climate. First‐order and second‐order maximum flooding surfaces define a regional sequence stratigraphic framework, subdividing the Roseneath–Epsilon–Murteree strata into four sequence units (SU1, SU2, SU3 and SU4), deposited during four phases (I, II, III and IV). Cyclic stacking patterns observed in both cores and wireline logs reveal two transgressive–regressive cycles. Palaeogeographical maps of the four depositional phases suggest that the Roseneath–Epsilon–Murteree strata were dominated by a lacustrine system with some delta and mire deposits. Rivers primarily drained towards the south/south‐west from the Gidgealpa, Merrimelia, Packsaddle and Innamincka ridges (‘GMI Trend’) as indicated by decreasing sandstone percentages and increasing gross unit isopach maps. The deposition of the Roseneath–Epsilon–Murteree strata was primarily controlled by basin subsidence. Additionally, palaeoclimate trends and extensive glaciation in the Permian played important roles in providing sediments and affecting lake level changes. The lake system recorded by the Roseneath–Epsilon–Murteree strata serves as an analogue for other fluvial–deltaic–lacustrine systems in basins worldwide. A multidisciplinary approach, similar to the one utilized in this study, can help to elucidate their evolution and aid in resource prediction.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"168 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141873131","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}
Ziv Mor, Gil Noy, Haggai Eyal, Ido Sirota, Roie Ezraty, Efrat Morin, Nadav G. Lensky
Thick‐bedded halite sequences in the geological record are characterized by lateral variations, reflecting spatiotemporal variations in environmental forcing. Although temporal variations have been examined over seasonal scales or longer durations, there is a paucity of information regarding the dynamics of halite deposition at shorter durations of days and hours. Additionally, the influence of water discharges and surface salinity gradients remains poorly understood. Here, for the first time, in situ, hourly to weekly halite accumulation rates were measured on the Dead Sea floor (ca 20 m water depth), the only modern deep and hypersaline water body. Novel underwater photography methods were developed to directly observe halite precipitation at the lake floor, coeval with monitoring of the environmental drives, i.e. evaporation, meteorological and limnological conditions. Two fundamental environments were explored: a diluted plume environment arising from spring discharge; and a mixed hypersaline environment. The focus was on deposition during winter when the halite accumulation rate is highest, and the relationship between evaporation and halite accumulation is most straightforward since the water column is vertically uniform. Significant spatial variations in halite accumulation were found between the two environments, along with hourly variations in each environment. In the mixed hypersaline environment, over intra‐diurnal timescales, evaporation plays a more significant role in halite precipitation, whereas temperature has a greater impact on seasonal changes. In the diluted plume environment, the stability of the buoyant plume controls the rate of halite deposition; during windstorms, the plume is stirred, with higher surface water salinity and higher rate of halite accumulation. However, under calm winds, the plume is stable, with diluted surface water, and the rate of halite accumulation is a few times lower. Following these new findings, the implications for the interpretation of halite deposits are discussed.
{"title":"Hourly to weekly variations in halite precipitation from the hypersaline Dead Sea: The role of evaporation, water cooling and freshwater plume stability","authors":"Ziv Mor, Gil Noy, Haggai Eyal, Ido Sirota, Roie Ezraty, Efrat Morin, Nadav G. Lensky","doi":"10.1111/sed.13220","DOIUrl":"https://doi.org/10.1111/sed.13220","url":null,"abstract":"Thick‐bedded halite sequences in the geological record are characterized by lateral variations, reflecting spatiotemporal variations in environmental forcing. Although temporal variations have been examined over seasonal scales or longer durations, there is a paucity of information regarding the dynamics of halite deposition at shorter durations of days and hours. Additionally, the influence of water discharges and surface salinity gradients remains poorly understood. Here, for the first time, <jats:italic>in situ</jats:italic>, hourly to weekly halite accumulation rates were measured on the Dead Sea floor (<jats:italic>ca</jats:italic> 20 m water depth), the only modern deep and hypersaline water body. Novel underwater photography methods were developed to directly observe halite precipitation at the lake floor, coeval with monitoring of the environmental drives, i.e. evaporation, meteorological and limnological conditions. Two fundamental environments were explored: a diluted plume environment arising from spring discharge; and a mixed hypersaline environment. The focus was on deposition during winter when the halite accumulation rate is highest, and the relationship between evaporation and halite accumulation is most straightforward since the water column is vertically uniform. Significant spatial variations in halite accumulation were found between the two environments, along with hourly variations in each environment. In the mixed hypersaline environment, over intra‐diurnal timescales, evaporation plays a more significant role in halite precipitation, whereas temperature has a greater impact on seasonal changes. In the diluted plume environment, the stability of the buoyant plume controls the rate of halite deposition; during windstorms, the plume is stirred, with higher surface water salinity and higher rate of halite accumulation. However, under calm winds, the plume is stable, with diluted surface water, and the rate of halite accumulation is a few times lower. Following these new findings, the implications for the interpretation of halite deposits are discussed.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"22 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141746489","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}
Jeff Peakall, JAMES L. Best, Jaco H. Baas, Paul B. Wignall, David M. Hodgson, Piotr Łapcik
Sole structures on the base of turbidites, and other bed types, are typically classified into scour marks and tool marks, such as flutes, grooves, skim marks and prod marks. Yet, there are a range of other common sole marks that are unrelated to scouring or tools, and whose origin is poorly understood. Prominent among these sole structures are longitudinal ridges and furrows, and ‘dinosaur leather’ structures associated with mud ripples. Herein, these features are described and it is argued that they are the product of deformation of the substrate during a sediment gravity flow event. In these flow‐induced interfacial deformation structures (FIDS), a soft cohesive substrate undergoes deformation in response to a buoyant force induced by the denser basal component of an overriding flow, and the flow interacts with this buoyant deformation through shear to remould the substrate. Variations in the relative strength of these buoyant and shear‐induced forces explain the wide range of FIDS that can form. This FIDS model reinterprets the formation of longitudinal ridges and furrows, which have previously been classified as scour marks, and explains their distinctive spatial patterns. Furthermore, the new model builds on the seminal work of Dżułyński and colleagues in the 1960s and 1970s, who identified that these structures contain key palaeocurrent information, and it is argued that such information is largely under‐utilized. Importantly, alongside their utility as palaeocurrent indicators, FIDS provide insights into the rheology of the substrate at the time of their formation, and thus the nature of basal flow conditions in the formative flows.
{"title":"Flow‐induced interfacial deformation structures (FIDS): Implications for the interpretation of palaeocurrents, flow dynamics and substrate rheology","authors":"Jeff Peakall, JAMES L. Best, Jaco H. Baas, Paul B. Wignall, David M. Hodgson, Piotr Łapcik","doi":"10.1111/sed.13219","DOIUrl":"https://doi.org/10.1111/sed.13219","url":null,"abstract":"Sole structures on the base of turbidites, and other bed types, are typically classified into scour marks and tool marks, such as flutes, grooves, skim marks and prod marks. Yet, there are a range of other common sole marks that are unrelated to scouring or tools, and whose origin is poorly understood. Prominent among these sole structures are longitudinal ridges and furrows, and ‘dinosaur leather’ structures associated with mud ripples. Herein, these features are described and it is argued that they are the product of deformation of the substrate during a sediment gravity flow event. In these flow‐induced interfacial deformation structures (FIDS), a soft cohesive substrate undergoes deformation in response to a buoyant force induced by the denser basal component of an overriding flow, and the flow interacts with this buoyant deformation through shear to remould the substrate. Variations in the relative strength of these buoyant and shear‐induced forces explain the wide range of FIDS that can form. This FIDS model reinterprets the formation of longitudinal ridges and furrows, which have previously been classified as scour marks, and explains their distinctive spatial patterns. Furthermore, the new model builds on the seminal work of Dżułyński and colleagues in the 1960s and 1970s, who identified that these structures contain key palaeocurrent information, and it is argued that such information is largely under‐utilized. Importantly, alongside their utility as palaeocurrent indicators, FIDS provide insights into the rheology of the substrate at the time of their formation, and thus the nature of basal flow conditions in the formative flows.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":"1 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141742413","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：