Pub Date : 2024-10-21DOI: 10.1016/j.geomorph.2024.109462
Storm surge barriers and closure dams influence estuarine morphology. Minimizing consequential ecological impacts requires a thorough understanding of the morphological adaptation mechanisms and associated time scales. Both are unraveled using three decades of morphological measurements on the adaptation of the Eastern Scheldt estuary (The Netherlands) to a storm surge barrier and closure dams. Both the storm surge barrier (through a decrease in cross-sectional area) and closure dams (inducing a reduction in surface area of the estuary) contributed to a reduction in tidal prism. As a smaller tidal prism implies a smaller equilibrium volume of the channels, the channels demand sediment to adjust. Consequently, by providing sediment to the channels, the intertidal flats erode. Erosion rates decreased while the sediment demand of the channels attenuated. This attenuation in sediment demand resulted mainly from tidal prism gains, caused by intertidal flat erosion and sea level rise. Erosion rates of the intertidal flats decreased further while they flattened to adapt to the reduced tidal velocities. Furthermore, storms caused erosion events, after which the long-term adaptation pace of intertidal flats suddenly reduced. Despite decreasing erosion, sea level rise enhances the drowning of intertidal flats in sediment-scarce estuarine systems, thereby pressuring these estuarine ecosystems and raising the need for mitigation measures.
{"title":"Response of estuarine morphology to storm surge barriers, closure dams and sea level rise","authors":"","doi":"10.1016/j.geomorph.2024.109462","DOIUrl":"10.1016/j.geomorph.2024.109462","url":null,"abstract":"<div><div>Storm surge barriers and closure dams influence estuarine morphology. Minimizing consequential ecological impacts requires a thorough understanding of the morphological adaptation mechanisms and associated time scales. Both are unraveled using three decades of morphological measurements on the adaptation of the Eastern Scheldt estuary (The Netherlands) to a storm surge barrier and closure dams. Both the storm surge barrier (through a decrease in cross-sectional area) and closure dams (inducing a reduction in surface area of the estuary) contributed to a reduction in tidal prism. As a smaller tidal prism implies a smaller equilibrium volume of the channels, the channels demand sediment to adjust. Consequently, by providing sediment to the channels, the intertidal flats erode. Erosion rates decreased while the sediment demand of the channels attenuated. This attenuation in sediment demand resulted mainly from tidal prism gains, caused by intertidal flat erosion and sea level rise. Erosion rates of the intertidal flats decreased further while they flattened to adapt to the reduced tidal velocities. Furthermore, storms caused erosion events, after which the long-term adaptation pace of intertidal flats suddenly reduced. Despite decreasing erosion, sea level rise enhances the drowning of intertidal flats in sediment-scarce estuarine systems, thereby pressuring these estuarine ecosystems and raising the need for mitigation measures.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-21DOI: 10.1016/j.geomorph.2024.109464
Mass transport Complexes (MTCs) form significant sediment accumulations in continental slopes, hold key insights for natural hazard prediction and offshore oil exploration. This paper uses high-definition 3D seismic data to reconstruct the seismic geomorphology and sedimentary dynamics of MTCs, meticulously exploring the depositional systems of the Tanaraki Basin, New Zealand. It deciphers by kinematic notation, seismic faciess, quantifies megaclast morphological characteristics, in conjunction with the basal slope and channel structure development as the migration or kinematics of MTCs. Five seismic facies categories and dynamic traits—compression ridges, thrust faults, slides, grooves and slope terraces are distinguished in MTCs. Based on attributes maps and geomorphological interpretations, MTCs is segmented into four zones, showing combined effects of levée, basal slopes, and megaclast clusters on its migration. Lithological and topographical variations along these features modulate erosion properties and MTCs mobility, with base height shifts guiding local migration trajectories. The results of megaclast parameters in Zones 1 and 3 tune our understanding of stress patterns and directionality shifts, highlighting the complex dynamics at play. Notably, the differential motion triggered by levees instigates longitudinal shear zones. At critical migration disparities, MTCs fracture at these weak points, discharging pore pressure and filling fractures with fines, birthing “promontory” formations marked by low-amplitude fills. This work, therefore, establishes a groundbreaking migratory model that synthesizes the impacts of levees height, rock type variability, and megaclasts accumulation intensity, depicting a fragmented migration pattern. This study not only enriches our grasp of MTCs behavior in deep-water contexts but also furnishes a robust scientific foundation and predictive tool for gauging the hazards that MTCs may pose to underwater structures, thus carrying substantial theoretical and applied significance.
{"title":"Mechanism and controlling factors of mass transport complexes migration: A case study of the mass transport complexes in the taranaki deep water basin, New Zealand","authors":"","doi":"10.1016/j.geomorph.2024.109464","DOIUrl":"10.1016/j.geomorph.2024.109464","url":null,"abstract":"<div><div>Mass transport Complexes (MTCs) form significant sediment accumulations in continental slopes, hold key insights for natural hazard prediction and offshore oil exploration. This paper uses high-definition 3D seismic data to reconstruct the seismic geomorphology and sedimentary dynamics of MTCs, meticulously exploring the depositional systems of the Tanaraki Basin, New Zealand. It deciphers by kinematic notation, seismic faciess, quantifies megaclast morphological characteristics, in conjunction with the basal slope and channel structure development as the migration or kinematics of MTCs. Five seismic facies categories and dynamic traits—compression ridges, thrust faults, slides, grooves and slope terraces are distinguished in MTCs. Based on attributes maps and geomorphological interpretations, MTCs is segmented into four zones, showing combined effects of levée, basal slopes, and megaclast clusters on its migration. Lithological and topographical variations along these features modulate erosion properties and MTCs mobility, with base height shifts guiding local migration trajectories. The results of megaclast parameters in Zones 1 and 3 tune our understanding of stress patterns and directionality shifts, highlighting the complex dynamics at play. Notably, the differential motion triggered by levees instigates longitudinal shear zones. At critical migration disparities, MTCs fracture at these weak points, discharging pore pressure and filling fractures with fines, birthing “promontory” formations marked by low-amplitude fills. This work, therefore, establishes a groundbreaking migratory model that synthesizes the impacts of levees height, rock type variability, and megaclasts accumulation intensity, depicting a fragmented migration pattern. This study not only enriches our grasp of MTCs behavior in deep-water contexts but also furnishes a robust scientific foundation and predictive tool for gauging the hazards that MTCs may pose to underwater structures, thus carrying substantial theoretical and applied significance.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-21DOI: 10.1016/j.geomorph.2024.109470
This paper aims to analyze and discuss what controls the geometry of incised alpine streams. For this, we construct a dataset comprising 39 cross-sections and the associated grain size measured in 10 rivers. We then examine each geometry to discuss the definition of bankfull and the associated hydraulics. We conclude that in these incised cross section, width remains nearly constant for a wide range of discharge, including discharges as low as discharge with an exceedance probability of 0.01 (discharge exceeded 3.65 days/yr). In particular, the hydraulics associated with geometric markers located in the lower part of each cross-section suggest that Parker's theory of a threshold forming Shields stress ratio τ*/τc* ≈ 1.5 established at bankfull for non-incised gravel bed rivers still keep its significance within the incised section. We suggest that the width W1.5 associated with the condition τ*/τc* ≈ 1.5 can be used as a reference width in alpine streams for river restoration or for risk management.
{"title":"Hydraulic geometry of Alpine streams channels","authors":"","doi":"10.1016/j.geomorph.2024.109470","DOIUrl":"10.1016/j.geomorph.2024.109470","url":null,"abstract":"<div><div>This paper aims to analyze and discuss what controls the geometry of incised alpine streams. For this, we construct a dataset comprising 39 cross-sections and the associated grain size measured in 10 rivers. We then examine each geometry to discuss the definition of bankfull and the associated hydraulics. We conclude that in these incised cross section, width remains nearly constant for a wide range of discharge, including discharges as low as discharge with an exceedance probability of 0.01 (discharge exceeded 3.65 days/yr). In particular, the hydraulics associated with geometric markers located in the lower part of each cross-section suggest that Parker's theory of a threshold forming Shields stress ratio τ*/τ<sub>c</sub>* ≈ 1.5 established at bankfull for non-incised gravel bed rivers still keep its significance within the incised section. We suggest that the width W<sub>1.5</sub> associated with the condition τ*/τ<sub>c</sub>* ≈ 1.5 can be used as a reference width in alpine streams for river restoration or for risk management.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-20DOI: 10.1016/j.geomorph.2024.109463
In regions with steep slopes, the classification of permanent gully (PG) into hillslope gullies (HG) and valley floor gullies (VG) was obvious before the study began. However, in the rolling hill region (slope < 5°), the difference between HG and VG was often overlooked. Moreover, there is no standardized approach for classifying gullies, which results in ambiguity regarding the impact of topography on various developmental stages of gullies and significantly impairs the effective management of gully erosion in the rolling hill region. We propose a remote sensing-based classification method to categorize 1081 PG into VG and HG in the cropland of the rolling hill region. The high-resolution satellite images (0.7 m) from 2010 and 2021 of all PGs were used to obtain the gully development rate and distribution patterns. Among these, 79 typical PGs were investigated using UAV to acquire high-resolution DEM (5 cm), which was used to analyze the relationship between the single or composite topographic factor and gully development rates. The results show that the proposed classification method can effectively recognize the VG and HG in the rolling hill region. The average length, area, and volume of the VG were found to be 2.31, 3.15, and 6.59 times that of the HG, respectively. The rate of gully head retreat, expansion area, and volume of the VG were also 1.59, 2.48, and 5.81 times faster than that of the HG, respectively. In HG and VG, the retreat rate of gully head (Δl) both showed a positive linear correlation with the distance from the gully head to the catchment divide (LA). The extension rate of gully area (Δa) was positively linearly and exponentially correlated with composite topographic factor SA (product of local slope (S) and contributing area above the gully head (A)). Additionally, the Δa of VG was strongly related to the shape and size of A, while the Δa of HG was strongly related to S. The gully volume expansion rate (ΔV) of both HG and VG was influenced by factors such as the existing size of the gully, the contributing area of the outlet (Ao), and the elevation difference from the outlet to the gully head (h). Hence, the changes in Δl and Δa for PG are primarily attributed to hydraulic erosion, while ΔV is influenced by both hydraulic and gravitational erosion. The study has shown the non-negligible influence of HG and VG in the rolling hill region. And the composite topographic factors can also better predict the PG development rate. This study contributes to the formulation of effective soil erosion prevention strategies and sustainable land management practices.
{"title":"Understanding the role of topography on valley floor gully and hillslope gully development in cropland of the rolling hill region of northeast China","authors":"","doi":"10.1016/j.geomorph.2024.109463","DOIUrl":"10.1016/j.geomorph.2024.109463","url":null,"abstract":"<div><div>In regions with steep slopes, the classification of permanent gully (PG) into hillslope gullies (HG) and valley floor gullies (VG) was obvious before the study began. However, in the rolling hill region (slope < 5°), the difference between HG and VG was often overlooked. Moreover, there is no standardized approach for classifying gullies, which results in ambiguity regarding the impact of topography on various developmental stages of gullies and significantly impairs the effective management of gully erosion in the rolling hill region. We propose a remote sensing-based classification method to categorize 1081 PG into VG and HG in the cropland of the rolling hill region. The high-resolution satellite images (0.7 m) from 2010 and 2021 of all PGs were used to obtain the gully development rate and distribution patterns. Among these, 79 typical PGs were investigated using UAV to acquire high-resolution DEM (5 cm), which was used to analyze the relationship between the single or composite topographic factor and gully development rates. The results show that the proposed classification method can effectively recognize the VG and HG in the rolling hill region. The average length, area, and volume of the VG were found to be 2.31, 3.15, and 6.59 times that of the HG, respectively. The rate of gully head retreat, expansion area, and volume of the VG were also 1.59, 2.48, and 5.81 times faster than that of the HG, respectively. In HG and VG, the retreat rate of gully head (Δ<em>l</em>) both showed a positive linear correlation with the distance from the gully head to the catchment divide (<em>L</em><sub><em>A</em></sub>). The extension rate of gully area (Δ<em>a</em>) was positively linearly and exponentially correlated with composite topographic factor <em>SA</em> (product of local slope (<em>S</em>) and contributing area above the gully head (<em>A</em>)). Additionally, the Δ<em>a</em> of VG was strongly related to the shape and size of <em>A</em>, while the Δ<em>a</em> of HG was strongly related to <em>S</em>. The gully volume expansion rate (Δ<em>V</em>) of both HG and VG was influenced by factors such as the existing size of the gully, the contributing area of the outlet (<em>A</em><sub><em>o</em></sub>), and the elevation difference from the outlet to the gully head (<em>h</em>). Hence, the changes in Δ<em>l</em> and Δ<em>a</em> for PG are primarily attributed to hydraulic erosion, while Δ<em>V</em> is influenced by both hydraulic and gravitational erosion. The study has shown the non-negligible influence of HG and VG in the rolling hill region. And the composite topographic factors can also better predict the PG development rate. This study contributes to the formulation of effective soil erosion prevention strategies and sustainable land management practices.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-17DOI: 10.1016/j.geomorph.2024.109461
Dust activity in Central Asia (CA) holds significant scientific interest due to their broad social and environmental impacts. Loess deposits in CA serve as crucial natural archives, recording regional atmospheric characteristics and dust dynamics. The oldest loess in CA has been discovered in southern Tajikistan. However, debates persist regarding the wind dynamics of the Tajikistan loess deposition, which motivates our current study. By analyzing grain sizes of the last glacial loess and previous loess records since 800 ka, we determined that the Tajikistan loess consisted of post-storm floating dust and fine-grained dust transported by the westerlies. The reduced grain sizes may indicate less frequent dust storms. Our results provided explanation for the influence of global ice volume changes on the dust dynamics in southern Tajikistan, primarily by modulating sea-level pressure differences between the Caspian Sea and Hindu Kush/Pamirs. These ice volume changes also intensified rapid atmospheric fluctuations in CA, suggesting a sensitive response of the latter to glacial boundary conditions. Moreover, although precipitation variations may influence dust activities, their impact appears to be minimal. Collectively, our findings offer vital insights into the formation of loess strata and the development of extensive modern loess landforms in southern CA.
中亚（CA）的沙尘活动具有广泛的社会和环境影响，因此在科学上具有重要意义。中亚地区的黄土沉积是重要的天然档案，记录着区域大气特征和沙尘动态。中亚最古老的黄土是在塔吉克斯坦南部发现的。然而，关于塔吉克斯坦黄土沉积的风力动态一直存在争议，这也是我们当前研究的动机。通过分析末次冰川期黄土的粒度和 800 ka 年以来的黄土记录，我们确定塔吉克斯坦黄土由风暴后的浮尘和西风带来的细粒尘埃组成。颗粒尺寸的减小可能表明沙尘暴的频率降低了。我们的研究结果解释了全球冰量变化对塔吉克斯坦南部沙尘动力学的影响，主要是通过调节里海和兴都库什/帕米尔之间的海平面压力差。这些冰量变化也加剧了中亚地区大气的快速波动，表明后者对冰川边界条件的敏感反应。此外，尽管降水变化可能会影响沙尘活动，但其影响似乎微乎其微。总之，我们的研究结果为了解黄土地层的形成和加利福尼亚南部广泛的现代黄土地貌的发展提供了重要的启示。
{"title":"Aeolian dust dynamics in southern Central Asia revealed by the multi-timescale loess records in southern Tajikistan","authors":"","doi":"10.1016/j.geomorph.2024.109461","DOIUrl":"10.1016/j.geomorph.2024.109461","url":null,"abstract":"<div><div>Dust activity in Central Asia (CA) holds significant scientific interest due to their broad social and environmental impacts. Loess deposits in CA serve as crucial natural archives, recording regional atmospheric characteristics and dust dynamics. The oldest loess in CA has been discovered in southern Tajikistan. However, debates persist regarding the wind dynamics of the Tajikistan loess deposition, which motivates our current study. By analyzing grain sizes of the last glacial loess and previous loess records since 800 ka, we determined that the Tajikistan loess consisted of post-storm floating dust and fine-grained dust transported by the westerlies. The reduced grain sizes may indicate less frequent dust storms. Our results provided explanation for the influence of global ice volume changes on the dust dynamics in southern Tajikistan, primarily by modulating sea-level pressure differences between the Caspian Sea and Hindu Kush/Pamirs. These ice volume changes also intensified rapid atmospheric fluctuations in CA, suggesting a sensitive response of the latter to glacial boundary conditions. Moreover, although precipitation variations may influence dust activities, their impact appears to be minimal. Collectively, our findings offer vital insights into the formation of loess strata and the development of extensive modern loess landforms in southern CA.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-17DOI: 10.1016/j.geomorph.2024.109459
<div><div>The use of analogues of previous river styles is highly significant for successful river restoration, yet some existing techniques available to assist practitioners are still not widely applied. We explore the use of Ground Penetrating Radar (GPR), to explore past river styles in an upland river valley in the UK, and explore the potential of the approach to reconstruct former channel pattern. Post-glacial evolution of upland floodplains has been influenced by temporal changes in vegetation, sediment supply and hydrological regime. Channel-floodplain morphodynamics over the Holocene were conditioned by glacial deposits, lateral interaction with slope processes and fluvial sediment reworking, changes in flow and sediment supply regimes driven by climatic change, and more recently direct and indirect anthropogenic activities, e.g. deforestation, floodplain land use and channel modification. Current drives towards river restoration often use floodplain topography as a guide to appraise such a planform state, however, reconstruction of former channel state is often restricted to surface features visible on historic maps and aerial photographs. This research focuses upon the floodplain of the upper Swindale Beck, Lake District, UK, which was recently restored to a planform design based on the recent meander pattern visible in floodplain topography. We show the potential of GPR to reconstruct a wider array of past channel pattern and evolution at a site characterised by largely aggradational conditions and consistent sediment supply from glacial deposits at the valley head. Analysis of GPR data from 40 intersecting GPR survey lines revealed several stratigraphic units, including gravel braidplains, berms, chutes and bars, several levels of larger channels and their layered fill as well as backwater deposits. These were interpreted as braided systems, dynamic wandering planform and single-thread meandering systems with spatial transitions conditioned by tributaries and valley slope. Optically Stimulated Luminescence (OSL) dates in combination with GIS analysis of valley slope, channel gradient and local valley floor aspect allowed the interpretation of individual evolutionary stages of river and floodplain development at Swindale over at least the last millennium and provides links to processes in the wider environment including the role of alluvial fans in supplying sediment and forcing channel migration. Such information can be particularly valuable for restoration projects to aid design of channel dimensions, planform configuration, channel gradient, substrate characteristics and connection with tributaries. While restoration generally aims to resemble a more natural reference state, specific targets may seek to improve a particular set of functionalities (e.g., ecological, flood and sediment management, recreational) which should be resilient to the consequences of ongoing climatic changes and should be achieved sustainably (e.g. locally so
{"title":"Using geophysical subsurface data for the reconstruction of valley-scale spatio-temporal floodplain evolution: Implications for upland river restoration","authors":"","doi":"10.1016/j.geomorph.2024.109459","DOIUrl":"10.1016/j.geomorph.2024.109459","url":null,"abstract":"<div><div>The use of analogues of previous river styles is highly significant for successful river restoration, yet some existing techniques available to assist practitioners are still not widely applied. We explore the use of Ground Penetrating Radar (GPR), to explore past river styles in an upland river valley in the UK, and explore the potential of the approach to reconstruct former channel pattern. Post-glacial evolution of upland floodplains has been influenced by temporal changes in vegetation, sediment supply and hydrological regime. Channel-floodplain morphodynamics over the Holocene were conditioned by glacial deposits, lateral interaction with slope processes and fluvial sediment reworking, changes in flow and sediment supply regimes driven by climatic change, and more recently direct and indirect anthropogenic activities, e.g. deforestation, floodplain land use and channel modification. Current drives towards river restoration often use floodplain topography as a guide to appraise such a planform state, however, reconstruction of former channel state is often restricted to surface features visible on historic maps and aerial photographs. This research focuses upon the floodplain of the upper Swindale Beck, Lake District, UK, which was recently restored to a planform design based on the recent meander pattern visible in floodplain topography. We show the potential of GPR to reconstruct a wider array of past channel pattern and evolution at a site characterised by largely aggradational conditions and consistent sediment supply from glacial deposits at the valley head. Analysis of GPR data from 40 intersecting GPR survey lines revealed several stratigraphic units, including gravel braidplains, berms, chutes and bars, several levels of larger channels and their layered fill as well as backwater deposits. These were interpreted as braided systems, dynamic wandering planform and single-thread meandering systems with spatial transitions conditioned by tributaries and valley slope. Optically Stimulated Luminescence (OSL) dates in combination with GIS analysis of valley slope, channel gradient and local valley floor aspect allowed the interpretation of individual evolutionary stages of river and floodplain development at Swindale over at least the last millennium and provides links to processes in the wider environment including the role of alluvial fans in supplying sediment and forcing channel migration. Such information can be particularly valuable for restoration projects to aid design of channel dimensions, planform configuration, channel gradient, substrate characteristics and connection with tributaries. While restoration generally aims to resemble a more natural reference state, specific targets may seek to improve a particular set of functionalities (e.g., ecological, flood and sediment management, recreational) which should be resilient to the consequences of ongoing climatic changes and should be achieved sustainably (e.g. locally so","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142531682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.geomorph.2024.109458
The continuous sedimentary records of the Beibuwan Basin preserve vital information on the interaction between Tethys and Pacific tectonic domains. The elusive interaction between the lithosphere and mantle significantly impacts the differential evolution of basins. However, the understanding of surface-mantle dynamic coupling beneath the Beibuwan Basin remains unclear. In this study, we analyze Cenozoic tectonic deformation, sedimentation, and mantle dynamic processes in the Beibuwan Basin in the northern South China Sea to clarify the nature of the tectonic-geomorphic transition during the late Eocene. Results show that the basin underwent late Eocene stratigraphic flexural folding, syn-rift transition from NE to EW orientated, and depocenter migration. The orientation of the primary controlling fault system during this period changed from NE-SW to NEE-SWW, the number of syn-depositional faults decreased from 368 to 172. The thickness of depocenters decreased from 5000 m to 1800 m, and the lacustrine Beibuwan Basin became shallower and wider. A comparison of the tectonic-structural history of the Beibuwan Basin with the history of plate subduction reconstructed from global geodynamic models shows that the late Eocene tectonic transition was closely related to changes in the stress field and the mantle wind related to oceanic plate subduction. We conclude that this enduring surface-mantle interaction associated with subduction of the Izanagi-Pacific mid-ocean ridge resulted in the late Eocene tectonic transition and geomorphic changes in the Beibuwan Basin.
{"title":"Late Eocene tectonic-geomorphic transition and its dynamic mechanism: Case study of the Beibuwan Basin, northern South China Sea","authors":"","doi":"10.1016/j.geomorph.2024.109458","DOIUrl":"10.1016/j.geomorph.2024.109458","url":null,"abstract":"<div><div>The continuous sedimentary records of the Beibuwan Basin preserve vital information on the interaction between Tethys and Pacific tectonic domains. The elusive interaction between the lithosphere and mantle significantly impacts the differential evolution of basins. However, the understanding of surface-mantle dynamic coupling beneath the Beibuwan Basin remains unclear. In this study, we analyze Cenozoic tectonic deformation, sedimentation, and mantle dynamic processes in the Beibuwan Basin in the northern South China Sea to clarify the nature of the tectonic-geomorphic transition during the late Eocene. Results show that the basin underwent late Eocene stratigraphic flexural folding, syn-rift transition from NE to EW orientated, and depocenter migration. The orientation of the primary controlling fault system during this period changed from NE-SW to NEE-SWW, the number of syn-depositional faults decreased from 368 to 172. The thickness of depocenters decreased from 5000 m to 1800 m, and the lacustrine Beibuwan Basin became shallower and wider. A comparison of the tectonic-structural history of the Beibuwan Basin with the history of plate subduction reconstructed from global geodynamic models shows that the late Eocene tectonic transition was closely related to changes in the stress field and the mantle wind related to oceanic plate subduction. We conclude that this enduring surface-mantle interaction associated with subduction of the Izanagi-Pacific mid-ocean ridge resulted in the late Eocene tectonic transition and geomorphic changes in the Beibuwan Basin.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.geomorph.2024.109456
The 494 km long Latvian coast consists of sandy sediments, which serve as an excellent proxy for past coastal events and environment. Our study explores these understudied sediments along the western coast of the Gulf of Riga and combines two sand quartz-wise methods: optically stimulated luminescence (OSL) dating and grain microtextures. We provide a new chronology and microsedimentary results to trace post-glacial storm events and discuss correlations within the Baltic Sea region and elsewhere in Europe. OSL ages reveal a wide time span between 10.38 ± 0.61 ka and 1.04 ± 0.05 ka BP, but their inconsistency in the profiles along with the onshore position of landforms and gravelly horizons argues for sediment relocation due to storm action. A first paleostorm phase is dated to between 7.6 ± 1.2 ka and 4.63 ± 0.27 ka, corresponding with a transgression of the Littorina Sea and the Holocene Thermal Maximum, and with a roughly estimated vertical sediment redeposition above 5 m similar with the recent storms in the region. Sedimentary record from microstudy supports intense storm activity, especially in sediments redeposited after 6.07 ± 0.51 ka, and it is seen through an increased number of cracked quartz grains, shiny grains and fresh surfaces combined with a limited number of V-shaped marks. Weaker storm action, recorded by a lower share of cracked grains in the sediments, occurred between 7.6 ± 1.2 ka and 6.07 ± 0.51 ka.
A second storm phase occurred at 1.44 ± 0.21 ka, corresponding with the post-Littorina, again with a performance of a weaker storm. Apart from the palaeostorm records, the beach ridges developed between 5.16 ± 0.33 ka and 4.47 ± 0.31 ka along with drier conditions when aeolian deposition took place twice: at 4.63 ± 0.27 ka and 1.55 ± 0.10 ka.
拉脱维亚 494 公里长的海岸由沙质沉积物组成，这些沉积物是过去海岸事件和环境的极佳替代物。我们的研究探索了里加湾西海岸这些未被充分研究的沉积物，并结合了两种砂质石英方法：光激发发光（OSL）测年和晶粒微质谱。我们提供了新的年代学和微沉积结果，以追溯冰川期后的风暴事件，并讨论了波罗的海地区和欧洲其他地区的相关性。OSL 年龄显示的时间跨度很大，介于 10.38 ± 0.61 ka 和 1.04 ± 0.05 ka BP 之间，但它们在剖面上的不一致性，以及地貌和砾石层的陆上位置，证明了风暴作用导致的沉积物迁移。第一个古风暴阶段的年代为 7.6 ± 1.2 ka 至 4.63 ± 0.27 ka，与 Littorina 海的横断和全新世热量最大期相对应，据粗略估计，5 米以上的垂直沉积物重新沉积与该地区最近的风暴相似。微观研究的沉积物记录支持强烈的风暴活动，特别是在 6.07 ± 0.51 ka 之后重新沉积的沉积物中，这可以从裂纹石英颗粒、闪亮颗粒和新鲜表面数量的增加以及数量有限的 V 形痕迹中看出。在 7.6 ± 1.2 ka 到 6.07 ± 0.51 ka 之间，出现了较弱的风暴作用，表现为沉积物中裂纹石英颗粒的数量减少。除了古风暴记录外，滩脊在 5.16 ± 0.33 ka 和 4.47 ± 0.31 ka 之间形成，当时的条件较为干燥，风化沉积发生了两次：4.63 ± 0.27 ka 和 1.55 ± 0.10 ka。
{"title":"Paleostorm redeposition and post-glacial coastal chronology in the eastern Baltic Sea, Latvia","authors":"","doi":"10.1016/j.geomorph.2024.109456","DOIUrl":"10.1016/j.geomorph.2024.109456","url":null,"abstract":"<div><div>The 494 km long Latvian coast consists of sandy sediments, which serve as an excellent proxy for past coastal events and environment. Our study explores these understudied sediments along the western coast of the Gulf of Riga and combines two sand quartz-wise methods: optically stimulated luminescence (OSL) dating and grain microtextures. We provide a new chronology and microsedimentary results to trace post-glacial storm events and discuss correlations within the Baltic Sea region and elsewhere in Europe. OSL ages reveal a wide time span between 10.38 ± 0.61 ka and 1.04 ± 0.05 ka BP, but their inconsistency in the profiles along with the onshore position of landforms and gravelly horizons argues for sediment relocation due to storm action. A first paleostorm phase is dated to between 7.6 ± 1.2 ka and 4.63 ± 0.27 ka, corresponding with a transgression of the Littorina Sea and the Holocene Thermal Maximum, and with a roughly estimated vertical sediment redeposition above 5 m similar with the recent storms in the region. Sedimentary record from microstudy supports intense storm activity, especially in sediments redeposited after 6.07 ± 0.51 ka, and it is seen through an increased number of cracked quartz grains, shiny grains and fresh surfaces combined with a limited number of V-shaped marks. Weaker storm action, recorded by a lower share of cracked grains in the sediments, occurred between 7.6 ± 1.2 ka and 6.07 ± 0.51 ka.</div><div>A second storm phase occurred at 1.44 ± 0.21 ka, corresponding with the post-Littorina, again with a performance of a weaker storm. Apart from the palaeostorm records, the beach ridges developed between 5.16 ± 0.33 ka and 4.47 ± 0.31 ka along with drier conditions when aeolian deposition took place twice: at 4.63 ± 0.27 ka and 1.55 ± 0.10 ka.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.1016/j.geomorph.2024.109455
Wind-blown coral sand movement is common in the marine coral sand island environment but received much less research attention compared to desert and coastal sands. We used the particle image velocimetry technique with wind tunnel experiments to determine the decay trends of the particle number density, nominal particle area density, and actual particle area density with height for wind-blown coral sands from the South China Sea. Then, a new morphology factor FM that consists of volume V, density ρs, drag coefficient CD, and projected area A of sand particles, was defined to evaluate the influences of particle characteristics on wind-blown sand movement and the results were compared with those of quartz sands from an inland desert. We found that the average FM of coral sands is more comparable to that of coarse quartz sands than smaller size groups. Coral sands tend to move nearer the surface during aeolian processes compared to smaller quartz ones due to their larger FM. The decay rate of particle number density of coral sands with height is similar to that of coarse (0.8–1 mm) quartz sands, but significantly larger than that of smaller quartz ones. The decay rate of the actual particle area density of coral sands with height is larger than that of their nominal particle area density, so that significant deviations may exist if a fixed particle size and spherical shape are assumed to study wind-blown particle movement. The present work contributes to understand the effect of particle characteristics on the wind-blown sand movement from a physical mechanism perspective for both desert quartz sands and marine coral sands.
风吹珊瑚沙运动在海洋珊瑚沙岛环境中很常见，但与沙漠和海岸沙相比，其研究关注度要低得多。我们利用颗粒图像测速技术和风洞实验，确定了南海风吹珊瑚沙的颗粒数密度、名义颗粒面积密度和实际颗粒面积密度随高度变化的衰减趋势。然后，定义了由沙粒体积 V、密度 ρs、阻力系数 CD 和投影面积 A 组成的新形态因子 FM，以评估颗粒特征对风吹沙运动的影响，并将结果与内陆沙漠石英沙的结果进行了比较。我们发现，珊瑚沙的平均调频与粗石英沙相比更接近。与较小的石英砂相比，珊瑚砂由于其较大的调频，在风化过程中往往更靠近地表。珊瑚砂的颗粒数密度随高度的衰减率与粗石英砂（0.8-1 毫米）相似，但明显大于小石英砂。珊瑚沙的实际颗粒面积密度随高度的衰减率大于其名义颗粒面积密度的衰减率，因此，如果假定研究风吹颗粒运动的颗粒大小和球形是固定的，则可能存在显著偏差。本研究有助于从物理机制的角度理解沙漠石英砂和海洋珊瑚砂的颗粒特征对风吹砂运动的影响。
{"title":"The variation of particle concentration with height of wind-blown coral sand","authors":"","doi":"10.1016/j.geomorph.2024.109455","DOIUrl":"10.1016/j.geomorph.2024.109455","url":null,"abstract":"<div><div>Wind-blown coral sand movement is common in the marine coral sand island environment but received much less research attention compared to desert and coastal sands. We used the particle image velocimetry technique with wind tunnel experiments to determine the decay trends of the particle number density, nominal particle area density, and actual particle area density with height for wind-blown coral sands from the South China Sea. Then, a new morphology factor <em>F</em><sub><em>M</em></sub> that consists of volume <em>V</em>, density <em>ρ</em><sub><em>s</em></sub>, drag coefficient <em>C</em><sub><em>D</em></sub>, and projected area <em>A</em> of sand particles, was defined to evaluate the influences of particle characteristics on wind-blown sand movement and the results were compared with those of quartz sands from an inland desert. We found that the average <em>F</em><sub><em>M</em></sub> of coral sands is more comparable to that of coarse quartz sands than smaller size groups. Coral sands tend to move nearer the surface during aeolian processes compared to smaller quartz ones due to their larger <em>F</em><sub><em>M</em></sub>. The decay rate of particle number density of coral sands with height is similar to that of coarse (0.8–1 mm) quartz sands, but significantly larger than that of smaller quartz ones. The decay rate of the actual particle area density of coral sands with height is larger than that of their nominal particle area density, so that significant deviations may exist if a fixed particle size and spherical shape are assumed to study wind-blown particle movement. The present work contributes to understand the effect of particle characteristics on the wind-blown sand movement from a physical mechanism perspective for both desert quartz sands and marine coral sands.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142531680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-12DOI: 10.1016/j.geomorph.2024.109453
Landslide volume plays a pivotal role in controlling landslide movement and potential damage. Although rainfall is widely recognized as one of the most important factors underlying landslide occurrence worldwide, its impact on landslide volume has been investigated only for individual landslide types. In this study, we show that rainfall characteristics and magnitude control the volume produced by both shallow and deep-seated landslides. A total of ten shallow and deep-seated landslides in Japan were compiled with volume, occurrence time, and rainfall data. Rainfall characteristics that triggered landslides were identified using the Soil Water Index and the three-layer tank model, which is a simple runoff model, and magnitude was quantified based on lag time. A strong positive correlation was found between lag time and landslide volume, indicating that landslide volume increases with increasing magnitude of rainfall to induce landslides. This study is the first attempt to suggest a relationship between rainfall magnitude and the volume produced by shallow and deep-seated landslides systematically and will promote the development of landslide risk management strategies.
{"title":"Rainfall characteristics and magnitude control the volume of shallow and deep-seated landslides: Inferences from analyses using a simple runoff model","authors":"","doi":"10.1016/j.geomorph.2024.109453","DOIUrl":"10.1016/j.geomorph.2024.109453","url":null,"abstract":"<div><div>Landslide volume plays a pivotal role in controlling landslide movement and potential damage. Although rainfall is widely recognized as one of the most important factors underlying landslide occurrence worldwide, its impact on landslide volume has been investigated only for individual landslide types. In this study, we show that rainfall characteristics and magnitude control the volume produced by both shallow and deep-seated landslides. A total of ten shallow and deep-seated landslides in Japan were compiled with volume, occurrence time, and rainfall data. Rainfall characteristics that triggered landslides were identified using the Soil Water Index and the three-layer tank model, which is a simple runoff model, and magnitude was quantified based on lag time. A strong positive correlation was found between lag time and landslide volume, indicating that landslide volume increases with increasing magnitude of rainfall to induce landslides. This study is the first attempt to suggest a relationship between rainfall magnitude and the volume produced by shallow and deep-seated landslides systematically and will promote the development of landslide risk management strategies.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142531681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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