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Manfred R Strecker - One of the best experts on this subject based on the ideXlab platform.
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climate driven sediment Aggradation and incision since the late pleistocene in the nw himalaya india
Earth and Planetary Science Letters, 2016Co-Authors: Saptarshi Dey, Dirk Scherler, Taylor F Schildgen, Hella Wittmann, Rasmus C Thiede, Bodo Bookhagen, Vikrant Jain, Manfred R StreckerAbstract:Abstract Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Kangra Basin (northwest Sub-Himalaya, India), upper Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on timescales of 103 to 105 yr. To evaluate the potential influence of climate change on these fluctuations, we compare the timing of Aggradation and incision phases recorded within remnant alluvial fans and terraces with climate archives. New surface-exposure dating of six terrace levels with in-situ cosmogenic 10Be indicates the onset of incision phases. Two terrace surfaces from the highest level (T1) sculpted into the oldest preserved alluvial fan (AF1) date back to 53.4 ± 3.2 ka and 43.0 ± 2.7 ka (1σ). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 18.6 ± 1.2 ka and 15.3 ± 0.9 ka , while terraces sculpted into the upper Pleistocene–Holocene fan (AF2) provide ages of 9.3 ± 0.4 ka (T3), 7.1 ± 0.4 ka (T4), 5.2 ± 0.4 ka (T5) and 3.6 ± 0.2 ka (T6). Together with previously published OSL ages yielding the timing of Aggradation, we find a correlation between variations in sediment transport with oxygen-isotope records from regions affected by the Indian Summer Monsoon. During periods of increased monsoon intensity and post-Last Glacial Maximum glacial retreat, Aggradation occurred in the Kangra Basin, likely due to high sediment flux, whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision.
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climatic controls on debris flow activity and sediment Aggradation the del medio fan nw argentina
Journal of Geophysical Research, 2016Co-Authors: Sara Savi, Dirk Scherler, Taylor F Schildgen, Stefanie Tofelde, Hella Wittmann, Jurgen Mey, Ricardo N Alonso, Manfred R StreckerAbstract:In the Central Andes, several studies on alluvial terraces and valley fills have linked sediment Aggradation to periods of enhanced sediment supply. However, debate continues over whether tectonic or climatic factors are most important in triggering the enhanced supply. The Del Medio catchment in the Humahuaca Basin (Eastern Cordillera, NW Argentina) is located within a transition zone between sub-humid and arid climates and hosts the only active debris-flow fan within this intermontane valley. By combining 10Be analyses of boulder and sediment samples within the Del Medio catchment, with regional morphometric measurements of nearby catchments, we identify the surface processes responsible for Aggradation in the Del Medio fan and their likely triggers. We find that the fan surface has been shaped by debris flows and channel avulsions during the last 400 years. Among potential tectonic, climatic, and autogenic factors that might influence deposition, our analyses point to a combination of several favorable factors that drive Aggradation. These are in particular the impact of occasional abundant rainfall on steep slopes in rock types prone to failure, located in a region characterized by relatively low rainfall amounts and limited transport capacity. These characteristics are primarily associated with the climatic transition zone between the humid foreland and the arid orogen interior, which creates an imbalance between sediment supply and sediment transfer. The conditions and processes that drive Aggradation in the Del Medio catchment today may provide a modern analog for the conditions and processes that drove Aggradation in other nearby tributaries in the past.
Dirk Scherler - One of the best experts on this subject based on the ideXlab platform.
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glacial influence on late pleistocene 10be derived paleo erosion rates in the north western himalaya india
Earth and Planetary Science Letters, 2020Co-Authors: Rene Kapannusch, Dirk Scherler, Georgina E King, Hella WittmannAbstract:Abstract Terrestrial cosmogenic nuclide concentrations in fluvial deposits allow estimation of paleo-erosion rates and reconstruction of the response of landscapes to climatic perturbations. In partly ice-covered landscapes, however, incorporation of subglacially-derived sediments that were shielded by ice from cosmic can lead to erroneous erosion rate calculations. Here, we combine in situ-produced 10Be-derived erosion rates, based on sand and pebbles from a fluvial fill terrace and the modern riverbed in the upper Yamuna catchment, with numerical ice flow modelling to quantify this bias. New luminescence and surface exposure ages suggest that Aggradation of the exposed deposits occurred between 29.9 ± 2.5 ka and 14.8 ± 2.8 ka. During most of the deposition, glaciers probably covered ∼19% of the catchment. 10Be concentrations of terrace sand samples differ from those of pebble samples. We obtained the lowest erosion rates from quartzite pebbles, which stem from low elevations, and the highest erosion rates from crystalline pebbles, which stem from high elevations in the Yamuna catchment. We explain these different erosion rates by differences in the steepness of the source areas, an effect that prevails throughout the entire Aggradation period despite significant former ice-cover. Sand samples, which are thought to be derived from all elevation parts of the catchment, however show lower 10Be concentrations during the Aggradation compared to present-day. We argue that this difference is due to a substantial subglacial origin of the sand during the Aggradation period, and not necessarily related to enhanced erosion. We conclude that Aggradation of the valley fill in the Yamuna catchment is most likely due to reduced discharge, and only marginally related to higher erosion rates during the late Pleistocene.
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climate driven sediment Aggradation and incision since the late pleistocene in the nw himalaya india
Earth and Planetary Science Letters, 2016Co-Authors: Saptarshi Dey, Dirk Scherler, Taylor F Schildgen, Hella Wittmann, Rasmus C Thiede, Bodo Bookhagen, Vikrant Jain, Manfred R StreckerAbstract:Abstract Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Kangra Basin (northwest Sub-Himalaya, India), upper Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on timescales of 103 to 105 yr. To evaluate the potential influence of climate change on these fluctuations, we compare the timing of Aggradation and incision phases recorded within remnant alluvial fans and terraces with climate archives. New surface-exposure dating of six terrace levels with in-situ cosmogenic 10Be indicates the onset of incision phases. Two terrace surfaces from the highest level (T1) sculpted into the oldest preserved alluvial fan (AF1) date back to 53.4 ± 3.2 ka and 43.0 ± 2.7 ka (1σ). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 18.6 ± 1.2 ka and 15.3 ± 0.9 ka , while terraces sculpted into the upper Pleistocene–Holocene fan (AF2) provide ages of 9.3 ± 0.4 ka (T3), 7.1 ± 0.4 ka (T4), 5.2 ± 0.4 ka (T5) and 3.6 ± 0.2 ka (T6). Together with previously published OSL ages yielding the timing of Aggradation, we find a correlation between variations in sediment transport with oxygen-isotope records from regions affected by the Indian Summer Monsoon. During periods of increased monsoon intensity and post-Last Glacial Maximum glacial retreat, Aggradation occurred in the Kangra Basin, likely due to high sediment flux, whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision.
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climate change versus landslide origin of fill terraces in a rapidly eroding bedrock landscape san gabriel river california
Geological Society of America Bulletin, 2016Co-Authors: Dirk Scherler, Edward J Rhodes, Michael P Lamb, Jean Philippe AvouacAbstract:Fill terraces along rivers represent the legacy of Aggradation periods that are most commonly attributed to climate change. In the North Fork of the San Gabriel River, an arid bedrock landscape in the San Gabriel Mountains, California, a series of prominent fill terraces was previously related to climate-change−induced pulses of hillslope sediment supply that temporarily and repeatedly overwhelmed river transport capacity during the Quaternary. Based on field observations, digital topographic analysis, and dating of Quaternary deposits, we suggest instead that valley Aggradation was spatially confined to the North Fork San Gabriel Canyon and was a consequence of the sudden supply of unconsolidated material to upstream reaches by one of the largest known landslides in the San Gabriel Mountains. New ^(10)Be-derived surface exposure ages from the landslide deposits, previously assumed to be early to middle Pleistocene in age, indicate at least three Holocene events at ca. 8−9 ka, ca. 4−5 ka, and ca. 0.5−1 ka. The oldest and presumably most extensive landslide predates the valley Aggradation period, which is constrained by existing ^(14)C ages and new luminescence ages to ca. 7−8 ka. The spatial distribution, morphology, and sedimentology of the river terraces are consistent with deposition from far-traveling debris flows that originated within, and mined, the landslide deposits. Valley Aggradation in the North Fork San Gabriel Canyon therefore resulted from locally enhanced sediment supply that temporarily overwhelmed river transport capacity, but the lack of similar deposits in other parts of the San Gabriel Mountains argues against a regional climatic signal. Our study highlights the potential for valley Aggradation by debris flows in arid bedrock landscapes downstream of landslides that occupy headwater areas.
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climatic controls on debris flow activity and sediment Aggradation the del medio fan nw argentina
Journal of Geophysical Research, 2016Co-Authors: Sara Savi, Dirk Scherler, Taylor F Schildgen, Stefanie Tofelde, Hella Wittmann, Jurgen Mey, Ricardo N Alonso, Manfred R StreckerAbstract:In the Central Andes, several studies on alluvial terraces and valley fills have linked sediment Aggradation to periods of enhanced sediment supply. However, debate continues over whether tectonic or climatic factors are most important in triggering the enhanced supply. The Del Medio catchment in the Humahuaca Basin (Eastern Cordillera, NW Argentina) is located within a transition zone between sub-humid and arid climates and hosts the only active debris-flow fan within this intermontane valley. By combining 10Be analyses of boulder and sediment samples within the Del Medio catchment, with regional morphometric measurements of nearby catchments, we identify the surface processes responsible for Aggradation in the Del Medio fan and their likely triggers. We find that the fan surface has been shaped by debris flows and channel avulsions during the last 400 years. Among potential tectonic, climatic, and autogenic factors that might influence deposition, our analyses point to a combination of several favorable factors that drive Aggradation. These are in particular the impact of occasional abundant rainfall on steep slopes in rock types prone to failure, located in a region characterized by relatively low rainfall amounts and limited transport capacity. These characteristics are primarily associated with the climatic transition zone between the humid foreland and the arid orogen interior, which creates an imbalance between sediment supply and sediment transfer. The conditions and processes that drive Aggradation in the Del Medio catchment today may provide a modern analog for the conditions and processes that drove Aggradation in other nearby tributaries in the past.
Jef Vandenberghe - One of the best experts on this subject based on the ideXlab platform.
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late quaternary Aggradation and incision in the headwaters of the yangtze river eastern tibetan plateau china
Geological Society of America Bulletin, 2021Co-Authors: Xianyan Wang, Xiaodong Miao, Jef VandenbergheAbstract:River Aggradation or incision at different spatial-temporal scales are governed by tectonics, climate change and surface processes which all adjust the ratio of sediment load to transport capacity ...
Frederik J Hilgen - One of the best experts on this subject based on the ideXlab platform.
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long eccentricity regulated climate control on fluvial incision and Aggradation in the palaeocene of north eastern montana usa
Sedimentology, 2020Co-Authors: Lars J Noorbergen, Antonio Turtu, Klaudia F Kuiper, C Kasse, Sverre Van Ginneken, Mark J Dekkers, Wout Krijgsman, Hemmo A Abels, Frederik J HilgenAbstract:Aggradation and fluvial incision controlled by downstream base-level changes at timescales of 10 to 500 kyr is incorporated in classic sequence stratigraphic models. However, upstream climate control on sediment supply and discharge variability causes fluvial incision and Aggradation as well. Orbital forcing often regulates climate change at 10 to 500 kyr timescales while tectonic processes such as flexural (un)loading exert a dominant control at timescales longer than 500 kyr. It remains challenging to attribute fluvial incision and Aggradation to upstream or downstream processes or disentangle allogenic from autogenic forcing, because time control is mostly limited in fluvial successions. The Palaeocene outcrops of the fluvial Lebo Shale Member in north-eastern Montana (Williston Basin, USA) constitute an exception. This study uses a distinctive tephra layer and two geomagnetic polarity reversals to create a 15 km long chronostratigraphic framework based on the correlation of twelve sections. Three Aggradation–incision sequences are identified with durations of approximately 400 kyr, suggesting a relation with long-eccentricity. This age control further reveals that incision occurred during the approach of – or during – a 405 kyr long-eccentricity minimum. A long-term relaxation of the hydrological cycle related to such an orbital phasing potentially exerts an upstream climate control on river incision. Upstream, an expanding vegetation cover is expected because of an increasingly constant moisture supply to source areas. Entrapping by vegetation led to a significantly reduced sediment supply relative to discharge, especially at times of low evapotranspiration. Hence, high discharges resulted in incision. This study assesses the long-eccentricity regulated climate control on fluvial Aggradation and incision in a new Aggradation–incision sequence model.
Hella Wittmann - One of the best experts on this subject based on the ideXlab platform.
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glacial influence on late pleistocene 10be derived paleo erosion rates in the north western himalaya india
Earth and Planetary Science Letters, 2020Co-Authors: Rene Kapannusch, Dirk Scherler, Georgina E King, Hella WittmannAbstract:Abstract Terrestrial cosmogenic nuclide concentrations in fluvial deposits allow estimation of paleo-erosion rates and reconstruction of the response of landscapes to climatic perturbations. In partly ice-covered landscapes, however, incorporation of subglacially-derived sediments that were shielded by ice from cosmic can lead to erroneous erosion rate calculations. Here, we combine in situ-produced 10Be-derived erosion rates, based on sand and pebbles from a fluvial fill terrace and the modern riverbed in the upper Yamuna catchment, with numerical ice flow modelling to quantify this bias. New luminescence and surface exposure ages suggest that Aggradation of the exposed deposits occurred between 29.9 ± 2.5 ka and 14.8 ± 2.8 ka. During most of the deposition, glaciers probably covered ∼19% of the catchment. 10Be concentrations of terrace sand samples differ from those of pebble samples. We obtained the lowest erosion rates from quartzite pebbles, which stem from low elevations, and the highest erosion rates from crystalline pebbles, which stem from high elevations in the Yamuna catchment. We explain these different erosion rates by differences in the steepness of the source areas, an effect that prevails throughout the entire Aggradation period despite significant former ice-cover. Sand samples, which are thought to be derived from all elevation parts of the catchment, however show lower 10Be concentrations during the Aggradation compared to present-day. We argue that this difference is due to a substantial subglacial origin of the sand during the Aggradation period, and not necessarily related to enhanced erosion. We conclude that Aggradation of the valley fill in the Yamuna catchment is most likely due to reduced discharge, and only marginally related to higher erosion rates during the late Pleistocene.
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climate driven sediment Aggradation and incision since the late pleistocene in the nw himalaya india
Earth and Planetary Science Letters, 2016Co-Authors: Saptarshi Dey, Dirk Scherler, Taylor F Schildgen, Hella Wittmann, Rasmus C Thiede, Bodo Bookhagen, Vikrant Jain, Manfred R StreckerAbstract:Abstract Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Kangra Basin (northwest Sub-Himalaya, India), upper Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on timescales of 103 to 105 yr. To evaluate the potential influence of climate change on these fluctuations, we compare the timing of Aggradation and incision phases recorded within remnant alluvial fans and terraces with climate archives. New surface-exposure dating of six terrace levels with in-situ cosmogenic 10Be indicates the onset of incision phases. Two terrace surfaces from the highest level (T1) sculpted into the oldest preserved alluvial fan (AF1) date back to 53.4 ± 3.2 ka and 43.0 ± 2.7 ka (1σ). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 18.6 ± 1.2 ka and 15.3 ± 0.9 ka , while terraces sculpted into the upper Pleistocene–Holocene fan (AF2) provide ages of 9.3 ± 0.4 ka (T3), 7.1 ± 0.4 ka (T4), 5.2 ± 0.4 ka (T5) and 3.6 ± 0.2 ka (T6). Together with previously published OSL ages yielding the timing of Aggradation, we find a correlation between variations in sediment transport with oxygen-isotope records from regions affected by the Indian Summer Monsoon. During periods of increased monsoon intensity and post-Last Glacial Maximum glacial retreat, Aggradation occurred in the Kangra Basin, likely due to high sediment flux, whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision.
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climatic controls on debris flow activity and sediment Aggradation the del medio fan nw argentina
Journal of Geophysical Research, 2016Co-Authors: Sara Savi, Dirk Scherler, Taylor F Schildgen, Stefanie Tofelde, Hella Wittmann, Jurgen Mey, Ricardo N Alonso, Manfred R StreckerAbstract:In the Central Andes, several studies on alluvial terraces and valley fills have linked sediment Aggradation to periods of enhanced sediment supply. However, debate continues over whether tectonic or climatic factors are most important in triggering the enhanced supply. The Del Medio catchment in the Humahuaca Basin (Eastern Cordillera, NW Argentina) is located within a transition zone between sub-humid and arid climates and hosts the only active debris-flow fan within this intermontane valley. By combining 10Be analyses of boulder and sediment samples within the Del Medio catchment, with regional morphometric measurements of nearby catchments, we identify the surface processes responsible for Aggradation in the Del Medio fan and their likely triggers. We find that the fan surface has been shaped by debris flows and channel avulsions during the last 400 years. Among potential tectonic, climatic, and autogenic factors that might influence deposition, our analyses point to a combination of several favorable factors that drive Aggradation. These are in particular the impact of occasional abundant rainfall on steep slopes in rock types prone to failure, located in a region characterized by relatively low rainfall amounts and limited transport capacity. These characteristics are primarily associated with the climatic transition zone between the humid foreland and the arid orogen interior, which creates an imbalance between sediment supply and sediment transfer. The conditions and processes that drive Aggradation in the Del Medio catchment today may provide a modern analog for the conditions and processes that drove Aggradation in other nearby tributaries in the past.