Pub Date : 2024-10-30DOI: 10.1016/j.geomorph.2024.109488
Willian R. Assis , Danilo S. Borges , Erick M. Franklin
We inquire into the morphodynamics of barchans under seasonal flows. For that, we carried out grain-scale numerical computations of a subaqueous barchan exposed to two-directional flows, and we varied the angle and frequency of oscillations. We show that when the frequency is lower than the inverse of the characteristic time for barchan formation, the dune adapts to the new flow direction and recovers the barchan shape while losing less grains than under one-directional flow. For higher frequencies, the dune has not enough time for adaptation and becomes more round while losing more grains. For both cases, we show, for the first time, the typical dynamics of grains (trajectories and forces). In particular, the round barchans are similar to the so-called occluded dunes observed on Mars, where seasons have very high frequencies compared to the dune timescale, different from Earth. Our results represent a possible explanation for that shape.
{"title":"On the effect of two-direction seasonal flows on barchans and the origin of occluded dunes","authors":"Willian R. Assis , Danilo S. Borges , Erick M. Franklin","doi":"10.1016/j.geomorph.2024.109488","DOIUrl":"10.1016/j.geomorph.2024.109488","url":null,"abstract":"<div><div>We inquire into the morphodynamics of barchans under seasonal flows. For that, we carried out grain-scale numerical computations of a subaqueous barchan exposed to two-directional flows, and we varied the angle and frequency of oscillations. We show that when the frequency is lower than the inverse of the characteristic time for barchan formation, the dune adapts to the new flow direction and recovers the barchan shape while losing less grains than under one-directional flow. For higher frequencies, the dune has not enough time for adaptation and becomes more round while losing more grains. For both cases, we show, for the first time, the typical dynamics of grains (trajectories and forces). In particular, the round barchans are similar to the so-called occluded dunes observed on Mars, where seasons have very high frequencies compared to the dune timescale, different from Earth. Our results represent a possible explanation for that shape.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109488"},"PeriodicalIF":3.1,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593555","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 : 2024-10-29DOI: 10.1016/j.geomorph.2024.109468
Nuocheng Li , Zhanju Lin , Huini Wang , Fujun Niu , Xingwen Fan , Jing Luo , Wenjiao Li , Xuyang Wu
With the global climate change, glaciers on the Qinghai-Tibet Plateau (QTP) and its adjacent mountainous regions are retreating rapidly, leading to an increase in active rock glaciers (ARGs) in front of glaciers. As crucial components of water resources in alpine regions and indicators of permafrost boundaries, ARGs reflect climatic and environmental changes on the QTP and its adjacent mountainous regions. However, the extensive scale of rock glacier development poses a challenge to field investigations and sampling, and manual visual interpretation requires substantial effort. Consequently, research on rock glacier cataloging and distribution characteristics across the entire area is scarce. This study statistically analyzed the geometric characteristics of ARGs using high-resolution GF-2 satellite images. It examined their spatial distribution and relationship with local factors. The findings reveal that 34,717 ARGs, covering an area of approximately 6873.54 km2, with an average area of 0.19 ± 0.24 km2, a maximum of 0.0012 km2, and a minimum of 4.6086 km2, were identified primarily in north-facing areas at elevations of 4300–5300 m and slopes of 9°–25°, predominantly in the Karakoram Mountains and the Himalayas. Notably, the largest concentration of ARGs was found on north-facing shady slopes, constituting about 42 % of the total amount, due to less solar radiation and lower near-surface temperatures favorable for interstitial ice preservation. This research enriches the foundational data on ARG distribution across the QTP and its adjacent mountainous regions, offering significant insights into the response mechanisms of rock glacier evolution to environmental changes and their environmental and engineering impacts.
{"title":"Inventory of active rock glaciers and their distribution characteristics on the Qinghai-Tibet Plateau and its adjacent mountainous regions","authors":"Nuocheng Li , Zhanju Lin , Huini Wang , Fujun Niu , Xingwen Fan , Jing Luo , Wenjiao Li , Xuyang Wu","doi":"10.1016/j.geomorph.2024.109468","DOIUrl":"10.1016/j.geomorph.2024.109468","url":null,"abstract":"<div><div>With the global climate change, glaciers on the Qinghai-Tibet Plateau (QTP) and its adjacent mountainous regions are retreating rapidly, leading to an increase in active rock glaciers (ARGs) in front of glaciers. As crucial components of water resources in alpine regions and indicators of permafrost boundaries, ARGs reflect climatic and environmental changes on the QTP and its adjacent mountainous regions. However, the extensive scale of rock glacier development poses a challenge to field investigations and sampling, and manual visual interpretation requires substantial effort. Consequently, research on rock glacier cataloging and distribution characteristics across the entire area is scarce. This study statistically analyzed the geometric characteristics of ARGs using high-resolution GF-2 satellite images. It examined their spatial distribution and relationship with local factors. The findings reveal that 34,717 ARGs, covering an area of approximately 6873.54 km<sup>2</sup>, with an average area of 0.19 ± 0.24 km<sup>2</sup>, a maximum of 0.0012 km<sup>2</sup>, and a minimum of 4.6086 km<sup>2</sup>, were identified primarily in north-facing areas at elevations of 4300–5300 m and slopes of 9°–25°, predominantly in the Karakoram Mountains and the Himalayas. Notably, the largest concentration of ARGs was found on north-facing shady slopes, constituting about 42 % of the total amount, due to less solar radiation and lower near-surface temperatures favorable for interstitial ice preservation. This research enriches the foundational data on ARG distribution across the QTP and its adjacent mountainous regions, offering significant insights into the response mechanisms of rock glacier evolution to environmental changes and their environmental and engineering impacts.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109468"},"PeriodicalIF":3.1,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571898","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 : 2024-10-29DOI: 10.1016/j.geomorph.2024.109466
C. Palmiotto , F. Muccini , E. Ficini , M.F. Loreto , M. Cuffaro
Oceanic geodiversity provides essential information on the dynamics of the Earth. Here, we focus on the geodiversity of three oceanic back-arc spreading centers: the Mariana Spreading Center, the Central-Southern Lau Basin spreading centers, and the East Scotia Ridge. We defined a method to identify their axial zones, obtaining spreading center depths along the basins. Results improve global plate boundary models and morphology variations, revealing that the average depths along the Mariana, East Scotia, and Lau Basin spreading ridges are 4.5, 3.5, and 2 km, respectively. We also measured new spreading rates based on five magnetic profiles crossing the three back-arc spreading centers, contributing to plate kinematic models. Furthermore, we computed subduction rates, including hinge velocities along the Mariana, South Sandwich, and Tonga Subductions, to understand the existing interactions between the subducting slab hinge motion and the kinematics of their related back-arc spreading centers. Our bathymetric, magnetic, and kinematic data show several differences among the Mariana, the East Scotia, and the Lau spreading centers, stressing the oceanic geodiversity in a similar geodynamic context. Our results also suggest a strong correlation between axial depth and full spreading rates along the back-arc spreading centers, a geological correspondence that allows a similar description of these divergent plate boundaries within the mid-ocean ridge classification. Finally, we show how hinge kinematics affects the relationship between convergence along subduction zones and back-arc spreading rates. All our findings contribute to understand how the oceanic geodiversity is directly related to geodynamic processes, increasing the knowledge of global tectonics.
{"title":"Oceanic geodiversity along back-arc spreading centers reveals analogies with mid-ocean ridges","authors":"C. Palmiotto , F. Muccini , E. Ficini , M.F. Loreto , M. Cuffaro","doi":"10.1016/j.geomorph.2024.109466","DOIUrl":"10.1016/j.geomorph.2024.109466","url":null,"abstract":"<div><div>Oceanic geodiversity provides essential information on the dynamics of the Earth. Here, we focus on the geodiversity of three oceanic back-arc spreading centers: the Mariana Spreading Center, the Central-Southern Lau Basin spreading centers, and the East Scotia Ridge. We defined a method to identify their axial zones, obtaining spreading center depths along the basins. Results improve global plate boundary models and morphology variations, revealing that the average depths along the Mariana, East Scotia, and Lau Basin spreading ridges are 4.5, 3.5, and 2 km, respectively. We also measured new spreading rates based on five magnetic profiles crossing the three back-arc spreading centers, contributing to plate kinematic models. Furthermore, we computed subduction rates, including hinge velocities along the Mariana, South Sandwich, and Tonga Subductions, to understand the existing interactions between the subducting slab hinge motion and the kinematics of their related back-arc spreading centers. Our bathymetric, magnetic, and kinematic data show several differences among the Mariana, the East Scotia, and the Lau spreading centers, stressing the oceanic geodiversity in a similar geodynamic context. Our results also suggest a strong correlation between axial depth and full spreading rates along the back-arc spreading centers, a geological correspondence that allows a similar description of these divergent plate boundaries within the mid-ocean ridge classification. Finally, we show how hinge kinematics affects the relationship between convergence along subduction zones and back-arc spreading rates. All our findings contribute to understand how the oceanic geodiversity is directly related to geodynamic processes, increasing the knowledge of global tectonics.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109466"},"PeriodicalIF":3.1,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142560773","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 : 2024-10-29DOI: 10.1016/j.geomorph.2024.109469
Pascal Bertran , Eric Andrieux , Sophie Leleu , Zoe Sicard-Delage , Benjamin Fores , Rachid Ouchaou , Pierre Weill , Jean-Yves Reynaud
The architecture and chronology of Late Pleistocene to Holocene alluvial deposits in the lower Garonne have been studied in details based on data (boreholes, trenches, ground-penetrating radar profiles, numerical dating) collected in quarries and during archaeological surveys. The preserved alluvial bodies, dated between ca. 38 ka and present, show that the river retained a meandering or anabranching pattern throughout this period, associated with the formation of lateral accretion packages and scroll bars in the convexity of meanders. Valley incision in connection to the LGM low sea level reached up to 19 m in the study area, and occurred between ca. 26 and 18 ka. Since ca. 18 ka, the lateral migration of meanders widened the plain without any significant incision of the Oligocene marl bedrock. The Early-Middle Holocene was characterized by the development of highly sinuous meanders, while sinuosity decreased in a late phase including the Little Ice Age. Comparison with other lowland European rivers shows that the persistence of a meandering or anabranching pattern during MIS 2 is not an isolated case. The documented examples are associated with rivers typified by low valley slope, or situated in southern regions unaffected by permafrost and characterized by dense vegetation. The latter conditions would not have led to a drastic change in river discharge and bedload transport during the Last Glacial, as was the case for more northerly rivers where braiding seems to have been common.
根据在采石场和考古调查中收集到的数据（钻孔、沟槽、探地雷达剖面图、数字测年法），对加龙河下游晚更新世至全新世冲积层的结构和年代学进行了详细研究。保存下来的冲积体的年代在大约 38 ka 年到现在之间，表明河流在这一时期一直保持着蜿蜒或无支流的模式，这与横向增生包和蜿蜒凸起处的涡条的形成有关。在研究区域内，与 LGM 低海平面有关的河谷侵蚀高达 19 米，发生在约 26 至 18 ka 之间。自大约自约 18 ka 时起，蜿蜒河道的横向迁移拓宽了平原，但没有对全新世泥灰岩基岩造成明显的侵蚀。全新世早中期的特点是蜿蜒曲折的蜿蜒河道的发展，而在包括小冰河时期在内的晚期，蜿蜒度有所下降。与欧洲其他低地河流的比较表明，在 MIS 2 期间，蜿蜒或无支流模式的持续存在并非个例。记录在案的例子都与河谷坡度较低的河流有关，或者与位于未受永久冻土影响且植被茂密的南部地区的河流有关。后一种情况在末次冰期不会导致河流排泄量和床面负荷迁移发生急剧变化，而在更靠北的河流中，辫状河似乎很常见。
{"title":"The Late Pleistocene - Holocene meandering lower Garonne River, southwest France: Architecture of the valley fill and chronology, comparison with other European rivers","authors":"Pascal Bertran , Eric Andrieux , Sophie Leleu , Zoe Sicard-Delage , Benjamin Fores , Rachid Ouchaou , Pierre Weill , Jean-Yves Reynaud","doi":"10.1016/j.geomorph.2024.109469","DOIUrl":"10.1016/j.geomorph.2024.109469","url":null,"abstract":"<div><div>The architecture and chronology of Late Pleistocene to Holocene alluvial deposits in the lower Garonne have been studied in details based on data (boreholes, trenches, ground-penetrating radar profiles, numerical dating) collected in quarries and during archaeological surveys. The preserved alluvial bodies, dated between ca. 38 ka and present, show that the river retained a meandering or anabranching pattern throughout this period, associated with the formation of lateral accretion packages and scroll bars in the convexity of meanders. Valley incision in connection to the LGM low sea level reached up to 19 m in the study area, and occurred between ca. 26 and 18 ka. Since ca. 18 ka, the lateral migration of meanders widened the plain without any significant incision of the Oligocene marl bedrock. The Early-Middle Holocene was characterized by the development of highly sinuous meanders, while sinuosity decreased in a late phase including the Little Ice Age. Comparison with other lowland European rivers shows that the persistence of a meandering or anabranching pattern during MIS 2 is not an isolated case. The documented examples are associated with rivers typified by low valley slope, or situated in southern regions unaffected by permafrost and characterized by dense vegetation. The latter conditions would not have led to a drastic change in river discharge and bedload transport during the Last Glacial, as was the case for more northerly rivers where braiding seems to have been common.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109469"},"PeriodicalIF":3.1,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661887","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 : 2024-10-29DOI: 10.1016/j.geomorph.2024.109467
Cihan Bayrakdar , Zeynel Çılğın , Faize Sarış , Serdar Yeşilyurt , Ferhat Keserci , Yusuf Büyükdeniz , Onur Halis , Christof Vockenhuber , Susan Ivy-Ochs , Naki Akçar
Glacial landforms in the southwestern part of the Anatolian Peninsula are found at lower elevations than the rest, suggesting that glaciers were present during the Late Pleistocene. Karadağ, located west of the Western Taurus Mountains, provides evidence of the climatic conditions that facilitated this extensive glaciation. It is characterized by numerous peaks exceeding 2300 m above sea level (asl), with the highest peak reaching 2418 m, making it the region's largest glaciation area. This high mountain mass is composed mainly of limestone and dolomite. This study focuses on the glacial landforms in Karadağ to reconstruct the Late Pleistocene glacial chronology and palaeoclimate of the Western Taurus Mountains. We employed detailed UAV photogrammetry, extensive fieldwork and mapping, surface exposure dating with cosmogenic 36Cl, meteorological measurements, palaeoglacier reconstruction, and palaeo-equilibrium line altitude (pELA) calculations. Karadağ, a topographic barrier to humid air masses from the Mediterranean Sea, ranks as the second wettest area in the Western Taurus Mountains. At a meteorological station we installed in Karadağ, an annual precipitation of 1700 mm or more was recorded, highlighting its significant precipitation. In Karadağ, we have identified two glacial valleys with a maximum length of 4.5 km and six cirques. The glaciers reached their maximum extent around 22.4 ± 2.8 ka during the Last Glacial Maximum (LGM), facilitated by the lowering of the pELA to 2090 m. During the LGM, the glaciers covered an area of approximately 3.5 km2 and reached a maximum thickness of about 140 m. Sample TRKR 10 at 2015 m probably belongs to the LGM period. Although a single sample does not conclude definitive conclusions, the presence of the moraine at its highest position indicates the maximum thickness of the glacier. Following the LGM, two more significant glacier advances occurred during the Lateglacial (15.5 ± 2.7 ka) and the Younger Dryas (12.4 ± 1.1 ka). During the late Pleistocene glaciations, and especially during the LGM, Karadağ probably received more precipitation than today, leading to the formation of glaciers at relatively lower elevations than on the Anatolian Peninsula.
{"title":"Late pleistocene glacial history of Mount Karadağ, SW Türkiye","authors":"Cihan Bayrakdar , Zeynel Çılğın , Faize Sarış , Serdar Yeşilyurt , Ferhat Keserci , Yusuf Büyükdeniz , Onur Halis , Christof Vockenhuber , Susan Ivy-Ochs , Naki Akçar","doi":"10.1016/j.geomorph.2024.109467","DOIUrl":"10.1016/j.geomorph.2024.109467","url":null,"abstract":"<div><div>Glacial landforms in the southwestern part of the Anatolian Peninsula are found at lower elevations than the rest, suggesting that glaciers were present during the Late Pleistocene. Karadağ, located west of the Western Taurus Mountains, provides evidence of the climatic conditions that facilitated this extensive glaciation. It is characterized by numerous peaks exceeding 2300 m above sea level (asl), with the highest peak reaching 2418 m, making it the region's largest glaciation area. This high mountain mass is composed mainly of limestone and dolomite. This study focuses on the glacial landforms in Karadağ to reconstruct the Late Pleistocene glacial chronology and palaeoclimate of the Western Taurus Mountains. We employed detailed UAV photogrammetry, extensive fieldwork and mapping, surface exposure dating with cosmogenic <sup>36</sup>Cl, meteorological measurements, palaeoglacier reconstruction, and palaeo-equilibrium line altitude (pELA) calculations. Karadağ, a topographic barrier to humid air masses from the Mediterranean Sea, ranks as the second wettest area in the Western Taurus Mountains. At a meteorological station we installed in Karadağ, an annual precipitation of 1700 mm or more was recorded, highlighting its significant precipitation. In Karadağ, we have identified two glacial valleys with a maximum length of 4.5 km and six cirques. The glaciers reached their maximum extent around 22.4 ± 2.8 ka during the Last Glacial Maximum (LGM), facilitated by the lowering of the pELA to 2090 m. During the LGM, the glaciers covered an area of approximately 3.5 km<sup>2</sup> and reached a maximum thickness of about 140 m. Sample TRKR 10 at 2015 m probably belongs to the LGM period. Although a single sample does not conclude definitive conclusions, the presence of the moraine at its highest position indicates the maximum thickness of the glacier. Following the LGM, two more significant glacier advances occurred during the Lateglacial (15.5 ± 2.7 ka) and the Younger Dryas (12.4 ± 1.1 ka). During the late Pleistocene glaciations, and especially during the LGM, Karadağ probably received more precipitation than today, leading to the formation of glaciers at relatively lower elevations than on the Anatolian Peninsula.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109467"},"PeriodicalIF":3.1,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142560772","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 : 2024-10-29DOI: 10.1016/j.geomorph.2024.109487
Sebastián Vivero , Christophe Lambiel
Due to the ongoing degradation of permafrost and the associated impacts on the stability of periglacial mountain slopes, there is a need to improve our understanding of the dynamics of rock glaciers over relatively short timescales. There is also a growing interest in the hydrological role of rock glaciers and other ice-debris landforms, as they can potentially store valuable amounts of ice. Despite the acceleration in rock glacier velocities observed primarily in the European Alps, annual and inter-annual changes in surface elevation and volume have so far escaped detailed quantification in monitoring programs. In this study, annual and biannual uncrewed aerial vehicle (UAV) surveys combined with structure-from-motion (SfM) photogrammetric techniques are used to derive high-resolution surface kinematics, elevation and volume changes of three rock glaciers in the Western Swiss Alps. Between 2016 and 2021, detailed digital elevation model (DEM) differencing revealed a high variability of mean annual elevation changes, reaching up to −0.19 ± 0.02 m/yr (2020−2021) at the Yettes Condjà B rock glacier, while elevation changes at the Les Cliosses rock glacier ranged from −0.05 ± 0.02 m/yr (2016–2017) to +0.014 ± 0.008 m/yr (2021−2021). In addition, the multi-temporal and very high-resolution topographic datasets revealed the presence of distinct rock glacier features, including superimposed lobes, lateral levees and flow divides, that could not be identified previously with traditional in-situ measurements and observations. Our results in terms of elevation and surface velocity changes highlight the importance of detailed and regular high-resolution monitoring for understanding the rapid evolution of active glaciers under the current degradation of mountain permafrost.
{"title":"Annual surface elevation changes of rock glaciers and their geomorphological significance: Examples from the Swiss Alps","authors":"Sebastián Vivero , Christophe Lambiel","doi":"10.1016/j.geomorph.2024.109487","DOIUrl":"10.1016/j.geomorph.2024.109487","url":null,"abstract":"<div><div>Due to the ongoing degradation of permafrost and the associated impacts on the stability of periglacial mountain slopes, there is a need to improve our understanding of the dynamics of rock glaciers over relatively short timescales. There is also a growing interest in the hydrological role of rock glaciers and other ice-debris landforms, as they can potentially store valuable amounts of ice. Despite the acceleration in rock glacier velocities observed primarily in the European Alps, annual and inter-annual changes in surface elevation and volume have so far escaped detailed quantification in monitoring programs. In this study, annual and biannual uncrewed aerial vehicle (UAV) surveys combined with structure-from-motion (SfM) photogrammetric techniques are used to derive high-resolution surface kinematics, elevation and volume changes of three rock glaciers in the Western Swiss Alps. Between 2016 and 2021, detailed digital elevation model (DEM) differencing revealed a high variability of mean annual elevation changes, reaching up to −0.19 ± 0.02 m/yr (2020−2021) at the Yettes Condjà B rock glacier, while elevation changes at the Les Cliosses rock glacier ranged from −0.05 ± 0.02 m/yr (2016–2017) to +0.014 ± 0.008 m/yr (2021−2021). In addition, the multi-temporal and very high-resolution topographic datasets revealed the presence of distinct rock glacier features, including superimposed lobes, lateral levees and flow divides, that could not be identified previously with traditional in-situ measurements and observations. Our results in terms of elevation and surface velocity changes highlight the importance of detailed and regular high-resolution monitoring for understanding the rapid evolution of active glaciers under the current degradation of mountain permafrost.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109487"},"PeriodicalIF":3.1,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571852","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 : 2024-10-28DOI: 10.1016/j.geomorph.2024.109483
Yingying Chen , Yiquan Li , Xianyan Wang , Rongqing Zhang , Wen Lai , Hanzhi Zhang , Hengzhi Lyu , Huayu Lu
Drainage divide migration, influenced by tectonic processes and climate change, significantly shapes geomorphological dynamics and sediment dispersal patterns. However, observing this phenomenon directly is challenging due to its prolonged and dynamic nature. While some researchers have employed simulations to investigate divide migration, these studies often lack the necessary empirical geological validation. The Qinling Mountains in central China, characterized by tectonic uplift and the subsidence of the Weihe Basin, serve as an exceptional natural laboratory for examining the intricate dynamics of the drainage divide between the Yellow and Yangtze Rivers. This study examines the migration history of the Qinling divide since the Cenozoic by analyzing detrital rutile UPb geochronology from Cenozoic strata within the Weihe Basin. Our results show that rutile UPb age peaks in the sediments deposited during the Eocene to Early Miocene are principally distributed at 110–300 Ma, 350–680 Ma, 800–840 Ma, and greater than 1000 Ma. From the Late Miocene to the Pliocene, the UPb age of detrital rutile is mainly distributed at 110–300 Ma and 350–680 Ma. The source signal change revealed by the Weihe Basin deposit sequence in the Late Miocene due to the gradual northward migration of the drainage divide. By examining the chronological evolution of detrital rutile UPb ages within the basin, we shed light on the trajectory of the Qinling divide's migration, offering new insights into the landscape evolution under the influence of tectonics and climate factors since the Cenozoic.
{"title":"Drainage divide migration between the Yellow and Yangtze Rivers at Eastern Qinling Mountains (central China): Insights from U-Pb ages of detrital rutile","authors":"Yingying Chen , Yiquan Li , Xianyan Wang , Rongqing Zhang , Wen Lai , Hanzhi Zhang , Hengzhi Lyu , Huayu Lu","doi":"10.1016/j.geomorph.2024.109483","DOIUrl":"10.1016/j.geomorph.2024.109483","url":null,"abstract":"<div><div>Drainage divide migration, influenced by tectonic processes and climate change, significantly shapes geomorphological dynamics and sediment dispersal patterns. However, observing this phenomenon directly is challenging due to its prolonged and dynamic nature. While some researchers have employed simulations to investigate divide migration, these studies often lack the necessary empirical geological validation. The Qinling Mountains in central China, characterized by tectonic uplift and the subsidence of the Weihe Basin, serve as an exceptional natural laboratory for examining the intricate dynamics of the drainage divide between the Yellow and Yangtze Rivers. This study examines the migration history of the Qinling divide since the Cenozoic by analyzing detrital rutile U<img>Pb geochronology from Cenozoic strata within the Weihe Basin. Our results show that rutile U<img>Pb age peaks in the sediments deposited during the Eocene to Early Miocene are principally distributed at 110–300 Ma, 350–680 Ma, 800–840 Ma, and greater than 1000 Ma. From the Late Miocene to the Pliocene, the U<img>Pb age of detrital rutile is mainly distributed at 110–300 Ma and 350–680 Ma. The source signal change revealed by the Weihe Basin deposit sequence in the Late Miocene due to the gradual northward migration of the drainage divide. By examining the chronological evolution of detrital rutile U<img>Pb ages within the basin, we shed light on the trajectory of the Qinling divide's migration, offering new insights into the landscape evolution under the influence of tectonics and climate factors since the Cenozoic.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109483"},"PeriodicalIF":3.1,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553112","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 : 2024-10-25DOI: 10.1016/j.geomorph.2024.109473
Xin He, Minghui Yu
Geomorphic abnormal responses of consecutive river bends to human activities, such as reservoir constructions and bank protection projects, have not been understood sufficiently. Based on the measured hydrological and topographic data, and remote sensing data, we investigated the morphological adjustments of 17 typical consecutive bends with different curvatures (the ratio of bend width B and bend radius R at the bend apex ranging from 0.22 to 1.96) in the Jingjiang Reach after the Three Gorges Dam (TGD) (2004–2021). The results show that these bends generally experienced inner bank scouring (IBS) and outer bank deposition (OBD). The distance to the dam affects the mechanism of IBS, from being primarily controlled by the water scouring intensity near the dam to the bend curvature and the regime adjustment of the upstream bend. Our results also show that the locations of IBS and OBD in the bends are related to the bend curvature. In sharp bends (B/R > 0.5), IBS occurs in the upper half of the bend, accompanied by OBD near the bend apex. In moderate bends (B/R ≤ 0.5), IBS occurs throughout the whole bend, with OBD near the bend entrance. A higher curvature bend tends to experience greater scouring of the inner bank near the bend apex. Moreover, the effect of upstream bends on downstream bends is revealed. In response to IBS and OBD in the upstream bend, the thalweg at the entrance shifts towards the inner bank, further promoting IBS in the downstream bend. OBD in the downstream bend is intensified by the residual reverse circulation of upstream bend. The results of this study can enhance the understanding of the evolution of meandering rivers in response to human activities, and may serve as a rational reference for managing the meandering rivers downstream of cascade reservoirs.
{"title":"Human interventions alter meandering channels evolution: Insights from the inner bank scouring and outer bank deposition in the Jingjiang Reach after the operation of the Three Gorges Dam","authors":"Xin He, Minghui Yu","doi":"10.1016/j.geomorph.2024.109473","DOIUrl":"10.1016/j.geomorph.2024.109473","url":null,"abstract":"<div><div>Geomorphic abnormal responses of consecutive river bends to human activities, such as reservoir constructions and bank protection projects, have not been understood sufficiently. Based on the measured hydrological and topographic data, and remote sensing data, we investigated the morphological adjustments of 17 typical consecutive bends with different curvatures (the ratio of bend width <em>B</em> and bend radius <em>R</em> at the bend apex ranging from 0.22 to 1.96) in the Jingjiang Reach after the Three Gorges Dam (TGD) (2004–2021). The results show that these bends generally experienced inner bank scouring (IBS) and outer bank deposition (OBD). The distance to the dam affects the mechanism of IBS, from being primarily controlled by the water scouring intensity near the dam to the bend curvature and the regime adjustment of the upstream bend. Our results also show that the locations of IBS and OBD in the bends are related to the bend curvature. In sharp bends (<em>B</em>/<em>R</em> > 0.5), IBS occurs in the upper half of the bend, accompanied by OBD near the bend apex. In moderate bends (<em>B</em>/<em>R</em> ≤ 0.5), IBS occurs throughout the whole bend, with OBD near the bend entrance. A higher curvature bend tends to experience greater scouring of the inner bank near the bend apex. Moreover, the effect of upstream bends on downstream bends is revealed. In response to IBS and OBD in the upstream bend, the thalweg at the entrance shifts towards the inner bank, further promoting IBS in the downstream bend. OBD in the downstream bend is intensified by the residual reverse circulation of upstream bend. The results of this study can enhance the understanding of the evolution of meandering rivers in response to human activities, and may serve as a rational reference for managing the meandering rivers downstream of cascade reservoirs.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109473"},"PeriodicalIF":3.1,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552653","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 : 2024-10-24DOI: 10.1016/j.geomorph.2024.109482
Christopher J. Baish , Alanna Post , Ashton M. Shortridge , Randall J. Schaetzl , Parker Hopkins , Anthony Bowman , Isabella Rabac , Bernard Frantz , Andrew O. Finley
We build on previous work which explained the origin of myriad gullies and incised channels on the dry, sandy uplands of northern Lower Michigan by invoking widespread permafrost. Indicators of permafrost (ice-wedge casts and patterned ground) are known from many sites across the region. Our study area, within an extensive reentrant of the retreating Laurentide Ice Sheet, had been particularly well positioned, geographically, for permafrost. Our goal was to characterize the geomorphic characteristics of the gullies on 72 large ridges, to address the hypothesis that they had formed in association with permafrost. Across the study area, thousands of dry, narrow channels and gullies occur in dense networks, typically with channels aligned directly downslope, in parallel drainage patterns. Most of the gullies exhibit only a minimal amount of incision (ca. 2–3 m), a nearly straight longitudinal profile, and lack a clear depositional fan at their mouth. Even where small fans are present, they are subtle and exhibit little down-fan textural sorting, as would be present in larger, more mature fluvial systems. Gully morphologies did not exhibit strong morphological differences as a function of aspect, as we would have expected for an erosional, periglacial system forming on fairly steep slopes. Nonetheless, in these sandy/gravelly sediments, we could find no other scenario that would have allowed for runoff and gully formation, except ice-rich permafrost that limited infiltration and promoted saturation of the active layer, and eventually, runoff. We conclude that the gullies formed via thermo-erosion into ice-rich permafrost, involving mostly fluvial processes but also some slope failure. Even though thermo-erosion can rapidly form deep gullies, our study area has mainly weak gully forms, perhaps because: (1) permafrost existed here only briefly, (2) the landscape was so cold and the permafrost so ice-rich that runoff was rare, (3) the permafrost on the sandy slopes remained somewhat permeable, limiting runoff, and/or (4) the paleoclimate was so dry that little water was available for sediment transport. We could find no evidence that the gullies developed within preexisting polygonal networks, as is happening today in polar regions under a warming climate. Thus, our study has implications for areas of the Arctic and Antarctic that are, today, experiencing rapid hydrological changes.
{"title":"Thousands of shallow, relict gullies indicate thermo-erosion on the sandy uplands of northern Lower Michigan during the Late Pleistocene","authors":"Christopher J. Baish , Alanna Post , Ashton M. Shortridge , Randall J. Schaetzl , Parker Hopkins , Anthony Bowman , Isabella Rabac , Bernard Frantz , Andrew O. Finley","doi":"10.1016/j.geomorph.2024.109482","DOIUrl":"10.1016/j.geomorph.2024.109482","url":null,"abstract":"<div><div>We build on previous work which explained the origin of myriad gullies and incised channels on the dry, sandy uplands of northern Lower Michigan by invoking widespread permafrost. Indicators of permafrost (ice-wedge casts and patterned ground) are known from many sites across the region. Our study area, within an extensive reentrant of the retreating Laurentide Ice Sheet, had been particularly well positioned, geographically, for permafrost. Our goal was to characterize the geomorphic characteristics of the gullies on 72 large ridges, to address the hypothesis that they had formed in association with permafrost. Across the study area, thousands of dry, narrow channels and gullies occur in dense networks, typically with channels aligned directly downslope, in parallel drainage patterns. Most of the gullies exhibit only a minimal amount of incision (ca. 2–3 m), a nearly straight longitudinal profile, and lack a clear depositional fan at their mouth. Even where small fans are present, they are subtle and exhibit little down-fan textural sorting, as would be present in larger, more mature fluvial systems. Gully morphologies did not exhibit strong morphological differences as a function of aspect, as we would have expected for an erosional, periglacial system forming on fairly steep slopes. Nonetheless, in these sandy/gravelly sediments, we could find no other scenario that would have allowed for runoff and gully formation, except ice-rich permafrost that limited infiltration and promoted saturation of the active layer, and eventually, runoff. We conclude that the gullies formed via thermo-erosion into ice-rich permafrost, involving mostly fluvial processes but also some slope failure. Even though thermo-erosion can rapidly form deep gullies, our study area has mainly weak gully forms, perhaps because: (1) permafrost existed here only briefly, (2) the landscape was so cold and the permafrost so ice-rich that runoff was rare, (3) the permafrost on the sandy slopes remained somewhat permeable, limiting runoff, and/or (4) the paleoclimate was so dry that little water was available for sediment transport. We could find no evidence that the gullies developed within preexisting polygonal networks, as is happening today in polar regions under a warming climate. Thus, our study has implications for areas of the Arctic and Antarctic that are, today, experiencing rapid hydrological changes.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109482"},"PeriodicalIF":3.1,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529707","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 : 2024-10-24DOI: 10.1016/j.geomorph.2024.109460
Andrea Brenna, Giacomo Poletto, Nicola Surian
In dynamic rivers the assessment of flood hazard related to geomorphological dynamics assumes crucial importance. Recently, some geomorphological approaches have been developed to assess channel dynamics in response to floods. In this study we explore the River Morphodynamic Corridors which include the current active channel and areas of the alluvial plain that may be (re)activated by channel dynamics during floods. In order to assess the effectiveness of such corridors for mapping flood hazard, we delineated the morphodynamic corridors along a river network of 74 km in the Cordevole River catchment (Italy) and compared the corridors with the channel changes that were triggered by a high-magnitude event (Vaia Storm) that hit the study area in October 2018. We observed that the morphodynamic corridors are capable to define areas where channel dynamics are most likely to occur and have proven satisfactorily effective in predicting channel widenings triggered by a severe flood. The results show that it is crucial to adopt different procedures for corridor delineation based on channel width, i.e., for small streams (width < 30 m) a more precautionary approach should be adopted that considers the entire alluvial plain as an area potentially affected by channel dynamics. The study highlighted an inherent limitation of the approach, since erosion that can affect valley slopes or fluvial terraces (i.e., widening of the alluvial plain) is not taken into account. This application represents the first validation of the River Morphodynamic Corridors approach through comparison with observed flood channel changes. Through this analysis, it can be inferred that, notwithstanding its relatively simple procedure, the approach allows a robust mapping and delineation of flood hazard due to river channel dynamics. The River Morphodynamic Corridors, when applied jointly with hydraulic model for assessing inundation processes, allow an overall assessment of flood hazard, particularly in dynamic river contexts.
{"title":"Assessing the effectiveness of “River Morphodynamic Corridors” for flood hazard mapping","authors":"Andrea Brenna, Giacomo Poletto, Nicola Surian","doi":"10.1016/j.geomorph.2024.109460","DOIUrl":"10.1016/j.geomorph.2024.109460","url":null,"abstract":"<div><div>In dynamic rivers the assessment of flood hazard related to geomorphological dynamics assumes crucial importance. Recently, some geomorphological approaches have been developed to assess channel dynamics in response to floods. In this study we explore the River Morphodynamic Corridors which include the current active channel and areas of the alluvial plain that may be (re)activated by channel dynamics during floods. In order to assess the effectiveness of such corridors for mapping flood hazard, we delineated the morphodynamic corridors along a river network of 74 km in the Cordevole River catchment (Italy) and compared the corridors with the channel changes that were triggered by a high-magnitude event (Vaia Storm) that hit the study area in October 2018. We observed that the morphodynamic corridors are capable to define areas where channel dynamics are most likely to occur and have proven satisfactorily effective in predicting channel widenings triggered by a severe flood. The results show that it is crucial to adopt different procedures for corridor delineation based on channel width, i.e., for small streams (width < 30 m) a more precautionary approach should be adopted that considers the entire alluvial plain as an area potentially affected by channel dynamics. The study highlighted an inherent limitation of the approach, since erosion that can affect valley slopes or fluvial terraces (i.e., widening of the alluvial plain) is not taken into account. This application represents the first validation of the River Morphodynamic Corridors approach through comparison with observed flood channel changes. Through this analysis, it can be inferred that, notwithstanding its relatively simple procedure, the approach allows a robust mapping and delineation of flood hazard due to river channel dynamics. The River Morphodynamic Corridors, when applied jointly with hydraulic model for assessing inundation processes, allow an overall assessment of flood hazard, particularly in dynamic river contexts.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"467 ","pages":"Article 109460"},"PeriodicalIF":3.1,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529711","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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