Riccardo Maitan, A. Finotello, D. Tognin, A. D’Alpaos, Christopher R. Fielding, A. Ielpi, M. Ghinassi
Bend cutoff is a fundamental process shaping meandering rivers. Despite the widely accepted differentiation between neck and chute cutoffs, a significant knowledge gap persists regarding the factors responsible for the occurrence of each cutoff regime and the specific conditions triggering the regime. Here, we used field and photogrammetric data derived from a global set of 22 meandering rivers, stretching more than 5500 km in total river length, to disentangle the controlling factors behind the cutoff regime in meandering rivers. We found that whether a meandering river forms a chute rather than neck meander cutoff depends primarily on the variability of overbank discharges. Short-lived, high-magnitude overbank floods promote the formation of chute cutoffs, aided by (though not required) reduced riparian vegetation density, enhanced stream power, and flow confinement within the river valley. In contrast, neck cutoffs are prevalent in rivers characterized by limited variations in bankfull hydrology, typically associated with low-magnitude, long-lasting overbank floods. Distinct cutoff regimes also discernibly affected floodplain geomorphology, with a chute regime resulting in more frequent cutoff occurrences. Our results suggest that human-induced alterations of river hydrologic regime can potentially cause fundamental shifts in the cutoff behavior of meandering rivers, thus affecting sediment residence time and carbon fluxes in alluvial floodplains.
{"title":"Hydrologically driven modulation of cutoff regime in meandering rivers","authors":"Riccardo Maitan, A. Finotello, D. Tognin, A. D’Alpaos, Christopher R. Fielding, A. Ielpi, M. Ghinassi","doi":"10.1130/g51783.1","DOIUrl":"https://doi.org/10.1130/g51783.1","url":null,"abstract":"Bend cutoff is a fundamental process shaping meandering rivers. Despite the widely accepted differentiation between neck and chute cutoffs, a significant knowledge gap persists regarding the factors responsible for the occurrence of each cutoff regime and the specific conditions triggering the regime. Here, we used field and photogrammetric data derived from a global set of 22 meandering rivers, stretching more than 5500 km in total river length, to disentangle the controlling factors behind the cutoff regime in meandering rivers. We found that whether a meandering river forms a chute rather than neck meander cutoff depends primarily on the variability of overbank discharges. Short-lived, high-magnitude overbank floods promote the formation of chute cutoffs, aided by (though not required) reduced riparian vegetation density, enhanced stream power, and flow confinement within the river valley. In contrast, neck cutoffs are prevalent in rivers characterized by limited variations in bankfull hydrology, typically associated with low-magnitude, long-lasting overbank floods. Distinct cutoff regimes also discernibly affected floodplain geomorphology, with a chute regime resulting in more frequent cutoff occurrences. Our results suggest that human-induced alterations of river hydrologic regime can potentially cause fundamental shifts in the cutoff behavior of meandering rivers, thus affecting sediment residence time and carbon fluxes in alluvial floodplains.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139778304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Riccardo Maitan, A. Finotello, D. Tognin, A. D’Alpaos, Christopher R. Fielding, A. Ielpi, M. Ghinassi
Bend cutoff is a fundamental process shaping meandering rivers. Despite the widely accepted differentiation between neck and chute cutoffs, a significant knowledge gap persists regarding the factors responsible for the occurrence of each cutoff regime and the specific conditions triggering the regime. Here, we used field and photogrammetric data derived from a global set of 22 meandering rivers, stretching more than 5500 km in total river length, to disentangle the controlling factors behind the cutoff regime in meandering rivers. We found that whether a meandering river forms a chute rather than neck meander cutoff depends primarily on the variability of overbank discharges. Short-lived, high-magnitude overbank floods promote the formation of chute cutoffs, aided by (though not required) reduced riparian vegetation density, enhanced stream power, and flow confinement within the river valley. In contrast, neck cutoffs are prevalent in rivers characterized by limited variations in bankfull hydrology, typically associated with low-magnitude, long-lasting overbank floods. Distinct cutoff regimes also discernibly affected floodplain geomorphology, with a chute regime resulting in more frequent cutoff occurrences. Our results suggest that human-induced alterations of river hydrologic regime can potentially cause fundamental shifts in the cutoff behavior of meandering rivers, thus affecting sediment residence time and carbon fluxes in alluvial floodplains.
{"title":"Hydrologically driven modulation of cutoff regime in meandering rivers","authors":"Riccardo Maitan, A. Finotello, D. Tognin, A. D’Alpaos, Christopher R. Fielding, A. Ielpi, M. Ghinassi","doi":"10.1130/g51783.1","DOIUrl":"https://doi.org/10.1130/g51783.1","url":null,"abstract":"Bend cutoff is a fundamental process shaping meandering rivers. Despite the widely accepted differentiation between neck and chute cutoffs, a significant knowledge gap persists regarding the factors responsible for the occurrence of each cutoff regime and the specific conditions triggering the regime. Here, we used field and photogrammetric data derived from a global set of 22 meandering rivers, stretching more than 5500 km in total river length, to disentangle the controlling factors behind the cutoff regime in meandering rivers. We found that whether a meandering river forms a chute rather than neck meander cutoff depends primarily on the variability of overbank discharges. Short-lived, high-magnitude overbank floods promote the formation of chute cutoffs, aided by (though not required) reduced riparian vegetation density, enhanced stream power, and flow confinement within the river valley. In contrast, neck cutoffs are prevalent in rivers characterized by limited variations in bankfull hydrology, typically associated with low-magnitude, long-lasting overbank floods. Distinct cutoff regimes also discernibly affected floodplain geomorphology, with a chute regime resulting in more frequent cutoff occurrences. Our results suggest that human-induced alterations of river hydrologic regime can potentially cause fundamental shifts in the cutoff behavior of meandering rivers, thus affecting sediment residence time and carbon fluxes in alluvial floodplains.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139837742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kangkang Li, Xiaoguang Qin, G. Plunkett, David Brown, Bing Xu, Lei Zhang, Zhaoyan Gu, Guijin Mu, H. Jia, Zhiqiang Yin, Jiaqi Liu
Reconstruction of hydrological fluctuations in arid regions has proven challenging due to a lack of reliable chronologic constraints on sparse geological archives. The aim of this study was to establish an independent record of hydrologic changes in the hyper-arid Tarim Basin (TB; northwest China) with high spatiotemporal resolution. We present comprehensive radiocarbon and tree-ring data sets of subfossilized plant remains in the TB compiled from geomorphological investigations of the paleochannels of the Tarim River (TR), the longest endorheic river in China, crossing the world’s second-largest shifting sand desert. Results show that the late medieval configuration of the TR basin was characterized by enhanced hydrological connectivity, as indicated by the formation of significant riparian forests in the desert regions at ca. 1170 CE. A distinct low-flow interval (ca. 1500−1650 CE) is identified for the first time, refining the period of a wetter-than-present TB. The present-day organization of streams in the lower TR was proto-formed after the dry period, possibly led by episodic flood-induced diversion. Our study describes the centennial-scale dynamics in the TR flow over the past millennium, offering a robust long-term context for hydrological assessment in the extensive drylands of the Asian interior.
{"title":"Hydrological fluctuations in the Tarim Basin, northwest China, over the past millennium","authors":"Kangkang Li, Xiaoguang Qin, G. Plunkett, David Brown, Bing Xu, Lei Zhang, Zhaoyan Gu, Guijin Mu, H. Jia, Zhiqiang Yin, Jiaqi Liu","doi":"10.1130/g51962.1","DOIUrl":"https://doi.org/10.1130/g51962.1","url":null,"abstract":"Reconstruction of hydrological fluctuations in arid regions has proven challenging due to a lack of reliable chronologic constraints on sparse geological archives. The aim of this study was to establish an independent record of hydrologic changes in the hyper-arid Tarim Basin (TB; northwest China) with high spatiotemporal resolution. We present comprehensive radiocarbon and tree-ring data sets of subfossilized plant remains in the TB compiled from geomorphological investigations of the paleochannels of the Tarim River (TR), the longest endorheic river in China, crossing the world’s second-largest shifting sand desert. Results show that the late medieval configuration of the TR basin was characterized by enhanced hydrological connectivity, as indicated by the formation of significant riparian forests in the desert regions at ca. 1170 CE. A distinct low-flow interval (ca. 1500−1650 CE) is identified for the first time, refining the period of a wetter-than-present TB. The present-day organization of streams in the lower TR was proto-formed after the dry period, possibly led by episodic flood-induced diversion. Our study describes the centennial-scale dynamics in the TR flow over the past millennium, offering a robust long-term context for hydrological assessment in the extensive drylands of the Asian interior.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139778083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kangkang Li, Xiaoguang Qin, G. Plunkett, David Brown, Bing Xu, Lei Zhang, Zhaoyan Gu, Guijin Mu, H. Jia, Zhiqiang Yin, Jiaqi Liu
Reconstruction of hydrological fluctuations in arid regions has proven challenging due to a lack of reliable chronologic constraints on sparse geological archives. The aim of this study was to establish an independent record of hydrologic changes in the hyper-arid Tarim Basin (TB; northwest China) with high spatiotemporal resolution. We present comprehensive radiocarbon and tree-ring data sets of subfossilized plant remains in the TB compiled from geomorphological investigations of the paleochannels of the Tarim River (TR), the longest endorheic river in China, crossing the world’s second-largest shifting sand desert. Results show that the late medieval configuration of the TR basin was characterized by enhanced hydrological connectivity, as indicated by the formation of significant riparian forests in the desert regions at ca. 1170 CE. A distinct low-flow interval (ca. 1500−1650 CE) is identified for the first time, refining the period of a wetter-than-present TB. The present-day organization of streams in the lower TR was proto-formed after the dry period, possibly led by episodic flood-induced diversion. Our study describes the centennial-scale dynamics in the TR flow over the past millennium, offering a robust long-term context for hydrological assessment in the extensive drylands of the Asian interior.
{"title":"Hydrological fluctuations in the Tarim Basin, northwest China, over the past millennium","authors":"Kangkang Li, Xiaoguang Qin, G. Plunkett, David Brown, Bing Xu, Lei Zhang, Zhaoyan Gu, Guijin Mu, H. Jia, Zhiqiang Yin, Jiaqi Liu","doi":"10.1130/g51962.1","DOIUrl":"https://doi.org/10.1130/g51962.1","url":null,"abstract":"Reconstruction of hydrological fluctuations in arid regions has proven challenging due to a lack of reliable chronologic constraints on sparse geological archives. The aim of this study was to establish an independent record of hydrologic changes in the hyper-arid Tarim Basin (TB; northwest China) with high spatiotemporal resolution. We present comprehensive radiocarbon and tree-ring data sets of subfossilized plant remains in the TB compiled from geomorphological investigations of the paleochannels of the Tarim River (TR), the longest endorheic river in China, crossing the world’s second-largest shifting sand desert. Results show that the late medieval configuration of the TR basin was characterized by enhanced hydrological connectivity, as indicated by the formation of significant riparian forests in the desert regions at ca. 1170 CE. A distinct low-flow interval (ca. 1500−1650 CE) is identified for the first time, refining the period of a wetter-than-present TB. The present-day organization of streams in the lower TR was proto-formed after the dry period, possibly led by episodic flood-induced diversion. Our study describes the centennial-scale dynamics in the TR flow over the past millennium, offering a robust long-term context for hydrological assessment in the extensive drylands of the Asian interior.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139837921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
João C. Duarte, Nicolas Riel, F. Rosas, Anton Popov, Christian Schuler, B. Kaus
Subduction initiation is a cornerstone of the Wilson cycle. It marks the turning point in an ocean’s lifetime, allowing its lithosphere to be recycled into the mantle. However, formation of new subduction zones in Atlantic-type oceans is challenging, given that it commonly involves the action of an external force, such as the slab pull from a nearby subduction zone, a far-field compression, or the impact of a plume. Notwithstanding, the Atlantic already has two subduction zones, the Lesser Antilles and the Scotia arcs. These subduction zones have been forced from the nearby Pacific subduction zones. The Gibraltar arc is another place where a subduction zone is invading the Atlantic. This corresponds to a direct migration of a subduction zone that developed in the closing Mediterranean Basin. Nevertheless, few authors consider the Gibraltar subduction to be still active because it has significantly slowed down in the past millions of years. Here, we use new gravity-driven geodynamic models that reproduce the evolution of the Western Mediterranean, show how the Gibraltar arc formed, and test if it is still active. The results suggest that the arc will propagate farther into the Atlantic after a period of quiescence. The models also show how a subduction zone starting in a closing ocean (Ligurian Ocean) can migrate into a new opening ocean (Atlantic) through a narrow oceanic corridor. Subduction invasion is likely a common mechanism of subduction initiation in Atlantic-type oceans and a fundamental process in the recent geological evolution of Earth.
{"title":"Gibraltar subduction zone is invading the Atlantic","authors":"João C. Duarte, Nicolas Riel, F. Rosas, Anton Popov, Christian Schuler, B. Kaus","doi":"10.1130/g51654.1","DOIUrl":"https://doi.org/10.1130/g51654.1","url":null,"abstract":"Subduction initiation is a cornerstone of the Wilson cycle. It marks the turning point in an ocean’s lifetime, allowing its lithosphere to be recycled into the mantle. However, formation of new subduction zones in Atlantic-type oceans is challenging, given that it commonly involves the action of an external force, such as the slab pull from a nearby subduction zone, a far-field compression, or the impact of a plume. Notwithstanding, the Atlantic already has two subduction zones, the Lesser Antilles and the Scotia arcs. These subduction zones have been forced from the nearby Pacific subduction zones. The Gibraltar arc is another place where a subduction zone is invading the Atlantic. This corresponds to a direct migration of a subduction zone that developed in the closing Mediterranean Basin. Nevertheless, few authors consider the Gibraltar subduction to be still active because it has significantly slowed down in the past millions of years. Here, we use new gravity-driven geodynamic models that reproduce the evolution of the Western Mediterranean, show how the Gibraltar arc formed, and test if it is still active. The results suggest that the arc will propagate farther into the Atlantic after a period of quiescence. The models also show how a subduction zone starting in a closing ocean (Ligurian Ocean) can migrate into a new opening ocean (Atlantic) through a narrow oceanic corridor. Subduction invasion is likely a common mechanism of subduction initiation in Atlantic-type oceans and a fundamental process in the recent geological evolution of Earth.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139780295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
João C. Duarte, Nicolas Riel, F. Rosas, Anton Popov, Christian Schuler, B. Kaus
Subduction initiation is a cornerstone of the Wilson cycle. It marks the turning point in an ocean’s lifetime, allowing its lithosphere to be recycled into the mantle. However, formation of new subduction zones in Atlantic-type oceans is challenging, given that it commonly involves the action of an external force, such as the slab pull from a nearby subduction zone, a far-field compression, or the impact of a plume. Notwithstanding, the Atlantic already has two subduction zones, the Lesser Antilles and the Scotia arcs. These subduction zones have been forced from the nearby Pacific subduction zones. The Gibraltar arc is another place where a subduction zone is invading the Atlantic. This corresponds to a direct migration of a subduction zone that developed in the closing Mediterranean Basin. Nevertheless, few authors consider the Gibraltar subduction to be still active because it has significantly slowed down in the past millions of years. Here, we use new gravity-driven geodynamic models that reproduce the evolution of the Western Mediterranean, show how the Gibraltar arc formed, and test if it is still active. The results suggest that the arc will propagate farther into the Atlantic after a period of quiescence. The models also show how a subduction zone starting in a closing ocean (Ligurian Ocean) can migrate into a new opening ocean (Atlantic) through a narrow oceanic corridor. Subduction invasion is likely a common mechanism of subduction initiation in Atlantic-type oceans and a fundamental process in the recent geological evolution of Earth.
{"title":"Gibraltar subduction zone is invading the Atlantic","authors":"João C. Duarte, Nicolas Riel, F. Rosas, Anton Popov, Christian Schuler, B. Kaus","doi":"10.1130/g51654.1","DOIUrl":"https://doi.org/10.1130/g51654.1","url":null,"abstract":"Subduction initiation is a cornerstone of the Wilson cycle. It marks the turning point in an ocean’s lifetime, allowing its lithosphere to be recycled into the mantle. However, formation of new subduction zones in Atlantic-type oceans is challenging, given that it commonly involves the action of an external force, such as the slab pull from a nearby subduction zone, a far-field compression, or the impact of a plume. Notwithstanding, the Atlantic already has two subduction zones, the Lesser Antilles and the Scotia arcs. These subduction zones have been forced from the nearby Pacific subduction zones. The Gibraltar arc is another place where a subduction zone is invading the Atlantic. This corresponds to a direct migration of a subduction zone that developed in the closing Mediterranean Basin. Nevertheless, few authors consider the Gibraltar subduction to be still active because it has significantly slowed down in the past millions of years. Here, we use new gravity-driven geodynamic models that reproduce the evolution of the Western Mediterranean, show how the Gibraltar arc formed, and test if it is still active. The results suggest that the arc will propagate farther into the Atlantic after a period of quiescence. The models also show how a subduction zone starting in a closing ocean (Ligurian Ocean) can migrate into a new opening ocean (Atlantic) through a narrow oceanic corridor. Subduction invasion is likely a common mechanism of subduction initiation in Atlantic-type oceans and a fundamental process in the recent geological evolution of Earth.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139840149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A big mantle wedge (BMW) is defined as the broad region of upper mantle above a stagnant slab in the mantle transition zone (MTZ). It is a common and significant structure within Earth’s interior at modern convergent plate margins as revealed by seismic data yet rarely identified in fossil convergent systems. We propose the existence of a BMW beneath the Western Mongolia Collage during the early to middle Paleozoic based on a comprehensive chronology of geological events that characterized the accretionary orogen in this region. The trench-arc system initially developed above a NE-dipping subduction zone, with subduction-related arc magmatism clustered at ca. 530−490 Ma and accumulations of flysch-like sequences from the Cambrian to early Silurian constituting the accretionary wedge of the Altai Zone. The westward migration of the arc was likely driven by slab rollback and trench retreat, leading to gradual formation of a BMW as the slab stagnated at the MTZ. The BMW influenced the tectonic evolution of the entire Western Mongolia Collage, inducing Ordovician−Silurian intraplate magmatism in regions inboard of the migrating magmatic arc and the potential opening of the Mongol-Okhotsk Ocean. Westward movement of the trench-arc continued until the Devonian, resulting in back-arc basin formation in the Chinese Altai and intraplate magmatism in the Hovd and Lake Zones of the Western Mongolia Collage, forming a trench−arc−back-arc and intraplate tectonic system. Mantle flow within the BMW is inferred to have impacted magmatism, basin migration, and the stress and thermal state of the overriding plate.
大地幔楔（BMW）被定义为地幔过渡带（MTZ）中停滞板块上方的广阔上地幔区域。地震数据显示，大地幔楔是现代汇聚板块边缘地球内部常见的重要结构，但在化石汇聚系统中却很少被发现。我们根据该地区增生造山运动地质事件的综合年表，提出在古生代早、中期，西蒙古褶皱带下存在一个 BMW。海沟-弧系统最初发育于东北倾俯冲带之上，与俯冲相关的弧岩浆活动聚集于约 530-490 Ma，并在约 530-490 Ma 处堆积。530-490 Ma，寒武纪至志留纪早期的萤石样序列堆积构成了阿尔泰区的增生楔。弧的西移很可能是由板块后退和海沟退缩驱动的，随着板块在MTZ的停滞，逐渐形成了BMW。BMW影响了整个蒙古西褶皱带的构造演化，在岩浆弧西移的内侧地区诱发了奥陶纪-志留纪板内岩浆活动，并有可能开辟蒙古-鄂霍次克洋。海沟-弧的西移一直持续到泥盆纪，在中国阿尔泰形成了弧后盆地，在蒙古西部褶皱的霍夫德区和湖泊区形成了板内岩浆活动，形成了海沟-弧-弧后-板内构造体系。据推断，BMW内部的岩浆流动对岩浆活动、盆地迁移以及凌空板块的应力和热力状态产生了影响。
{"title":"Recognizing big mantle wedges in deep time: Constraints from the Western Mongolia Collage in Central Asia","authors":"X. Cui, Peter A. Cawood, Min Sun, Guochun Zhao","doi":"10.1130/g51841.1","DOIUrl":"https://doi.org/10.1130/g51841.1","url":null,"abstract":"A big mantle wedge (BMW) is defined as the broad region of upper mantle above a stagnant slab in the mantle transition zone (MTZ). It is a common and significant structure within Earth’s interior at modern convergent plate margins as revealed by seismic data yet rarely identified in fossil convergent systems. We propose the existence of a BMW beneath the Western Mongolia Collage during the early to middle Paleozoic based on a comprehensive chronology of geological events that characterized the accretionary orogen in this region. The trench-arc system initially developed above a NE-dipping subduction zone, with subduction-related arc magmatism clustered at ca. 530−490 Ma and accumulations of flysch-like sequences from the Cambrian to early Silurian constituting the accretionary wedge of the Altai Zone. The westward migration of the arc was likely driven by slab rollback and trench retreat, leading to gradual formation of a BMW as the slab stagnated at the MTZ. The BMW influenced the tectonic evolution of the entire Western Mongolia Collage, inducing Ordovician−Silurian intraplate magmatism in regions inboard of the migrating magmatic arc and the potential opening of the Mongol-Okhotsk Ocean. Westward movement of the trench-arc continued until the Devonian, resulting in back-arc basin formation in the Chinese Altai and intraplate magmatism in the Hovd and Lake Zones of the Western Mongolia Collage, forming a trench−arc−back-arc and intraplate tectonic system. Mantle flow within the BMW is inferred to have impacted magmatism, basin migration, and the stress and thermal state of the overriding plate.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139844650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A big mantle wedge (BMW) is defined as the broad region of upper mantle above a stagnant slab in the mantle transition zone (MTZ). It is a common and significant structure within Earth’s interior at modern convergent plate margins as revealed by seismic data yet rarely identified in fossil convergent systems. We propose the existence of a BMW beneath the Western Mongolia Collage during the early to middle Paleozoic based on a comprehensive chronology of geological events that characterized the accretionary orogen in this region. The trench-arc system initially developed above a NE-dipping subduction zone, with subduction-related arc magmatism clustered at ca. 530−490 Ma and accumulations of flysch-like sequences from the Cambrian to early Silurian constituting the accretionary wedge of the Altai Zone. The westward migration of the arc was likely driven by slab rollback and trench retreat, leading to gradual formation of a BMW as the slab stagnated at the MTZ. The BMW influenced the tectonic evolution of the entire Western Mongolia Collage, inducing Ordovician−Silurian intraplate magmatism in regions inboard of the migrating magmatic arc and the potential opening of the Mongol-Okhotsk Ocean. Westward movement of the trench-arc continued until the Devonian, resulting in back-arc basin formation in the Chinese Altai and intraplate magmatism in the Hovd and Lake Zones of the Western Mongolia Collage, forming a trench−arc−back-arc and intraplate tectonic system. Mantle flow within the BMW is inferred to have impacted magmatism, basin migration, and the stress and thermal state of the overriding plate.
大地幔楔（BMW）被定义为地幔过渡带（MTZ）中停滞板块上方的广阔上地幔区域。地震数据显示，大地幔楔是现代汇聚板块边缘地球内部常见的重要结构，但在化石汇聚系统中却很少被发现。我们根据该地区增生造山运动地质事件的综合年表，提出在古生代早、中期，西蒙古褶皱带下存在一个 BMW。海沟-弧系统最初发育于东北倾俯冲带之上，与俯冲相关的弧岩浆活动聚集于约 530-490 Ma，并在约 530-490 Ma 处堆积。530-490 Ma，寒武纪至志留纪早期的萤石样序列堆积构成了阿尔泰区的增生楔。弧的西移很可能是由板块后退和海沟退缩驱动的，随着板块在MTZ的停滞，逐渐形成了BMW。BMW影响了整个蒙古西褶皱带的构造演化，在岩浆弧西移的内侧地区诱发了奥陶纪-志留纪板内岩浆活动，并有可能开辟蒙古-鄂霍次克洋。海沟-弧的西移一直持续到泥盆纪，在中国阿尔泰形成了弧后盆地，在蒙古西部褶皱的霍夫德区和湖泊区形成了板内岩浆活动，形成了海沟-弧-弧后-板内构造体系。据推断，BMW内部的岩浆流动对岩浆活动、盆地迁移以及凌空板块的应力和热力状态产生了影响。
{"title":"Recognizing big mantle wedges in deep time: Constraints from the Western Mongolia Collage in Central Asia","authors":"X. Cui, Peter A. Cawood, Min Sun, Guochun Zhao","doi":"10.1130/g51841.1","DOIUrl":"https://doi.org/10.1130/g51841.1","url":null,"abstract":"A big mantle wedge (BMW) is defined as the broad region of upper mantle above a stagnant slab in the mantle transition zone (MTZ). It is a common and significant structure within Earth’s interior at modern convergent plate margins as revealed by seismic data yet rarely identified in fossil convergent systems. We propose the existence of a BMW beneath the Western Mongolia Collage during the early to middle Paleozoic based on a comprehensive chronology of geological events that characterized the accretionary orogen in this region. The trench-arc system initially developed above a NE-dipping subduction zone, with subduction-related arc magmatism clustered at ca. 530−490 Ma and accumulations of flysch-like sequences from the Cambrian to early Silurian constituting the accretionary wedge of the Altai Zone. The westward migration of the arc was likely driven by slab rollback and trench retreat, leading to gradual formation of a BMW as the slab stagnated at the MTZ. The BMW influenced the tectonic evolution of the entire Western Mongolia Collage, inducing Ordovician−Silurian intraplate magmatism in regions inboard of the migrating magmatic arc and the potential opening of the Mongol-Okhotsk Ocean. Westward movement of the trench-arc continued until the Devonian, resulting in back-arc basin formation in the Chinese Altai and intraplate magmatism in the Hovd and Lake Zones of the Western Mongolia Collage, forming a trench−arc−back-arc and intraplate tectonic system. Mantle flow within the BMW is inferred to have impacted magmatism, basin migration, and the stress and thermal state of the overriding plate.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139784724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin S. Murphy, J. Caine, P. Bedrosian, Jade Crosbie
Three-dimensional magnetotelluric (MT) imaging in central Colorado revealed a set of north-striking high-conductivity tracks at lower-crustal (50−20 km) depths, with conductive finger-like structures rising off these tracks into the middle crust (20−5 km depth). We interpret these features to represent saline aqueous fluids and partial melt that are products of active extensional tectonomagmatism. These conductors are distributed over a wider region than the narrow corridor along which Rio Grande rift structures are traditionally mapped at the surface, and they consequently demarcate regions of the lower crust where accommodation of bulk extensional strain has concentrated conductive phases. Our observations reveal limitations in existing models of Rio Grande rift activity and may reflect unrecognized spatiotemporal variations in rift system evolution globally.
{"title":"Geoelectric evidence for a wide spatial footprint of active extension in central Colorado","authors":"Benjamin S. Murphy, J. Caine, P. Bedrosian, Jade Crosbie","doi":"10.1130/g51517.1","DOIUrl":"https://doi.org/10.1130/g51517.1","url":null,"abstract":"Three-dimensional magnetotelluric (MT) imaging in central Colorado revealed a set of north-striking high-conductivity tracks at lower-crustal (50−20 km) depths, with conductive finger-like structures rising off these tracks into the middle crust (20−5 km depth). We interpret these features to represent saline aqueous fluids and partial melt that are products of active extensional tectonomagmatism. These conductors are distributed over a wider region than the narrow corridor along which Rio Grande rift structures are traditionally mapped at the surface, and they consequently demarcate regions of the lower crust where accommodation of bulk extensional strain has concentrated conductive phases. Our observations reveal limitations in existing models of Rio Grande rift activity and may reflect unrecognized spatiotemporal variations in rift system evolution globally.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139848427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Coastal marsh loss is commonly attributed to changes in external forcings, such as an increase in sea-level rise rate or a reduction in sediment supply. Here we show that extensive marsh loss can be caused by internal mechanisms alone, and specifically by autogenic tidal choking. This occurs when the marsh fills in, increasing tidal dissipation by bed friction and eventually decreasing the tidal range in its landward section. The reduced tidal range decreases sediment import on the marsh platform and increases ponding, both of which lead to interior marsh loss even with modest sea-level rise rates. This process is predicted to occur in dissipative microtidal marshes, which are experiencing some of the fastest rates of marsh loss worldwide. Considering this mechanism is essential to understanding the relationship between marsh loss, sea-level rise, and sediment supply and to eventually predicting future marsh evolution.
{"title":"Tidal dissipation morphodynamic feedback triggers loss of microtidal marshes","authors":"S. Zapp, G. Mariotti","doi":"10.1130/g51798.1","DOIUrl":"https://doi.org/10.1130/g51798.1","url":null,"abstract":"Coastal marsh loss is commonly attributed to changes in external forcings, such as an increase in sea-level rise rate or a reduction in sediment supply. Here we show that extensive marsh loss can be caused by internal mechanisms alone, and specifically by autogenic tidal choking. This occurs when the marsh fills in, increasing tidal dissipation by bed friction and eventually decreasing the tidal range in its landward section. The reduced tidal range decreases sediment import on the marsh platform and increases ponding, both of which lead to interior marsh loss even with modest sea-level rise rates. This process is predicted to occur in dissipative microtidal marshes, which are experiencing some of the fastest rates of marsh loss worldwide. Considering this mechanism is essential to understanding the relationship between marsh loss, sea-level rise, and sediment supply and to eventually predicting future marsh evolution.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139790042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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