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Glacial influence on late Pleistocene 10Be-derived paleo-erosion rates in the north-western Himalaya, India

Kapannusch, René ; Scherler, Dirk ; King, Georgina ; Wittmann, Hella

Earth and planetary science letters, 2020-10, Vol.547, p.116441, Article 116441 [Periódico revisado por pares]

Elsevier B.V

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  • Título:
    Glacial influence on late Pleistocene 10Be-derived paleo-erosion rates in the north-western Himalaya, India
  • Autor: Kapannusch, René ; Scherler, Dirk ; King, Georgina ; Wittmann, Hella
  • Assuntos: climate change ; cosmogenic nuclides ; Himalaya ; late Pleistocene ; paleo-erosion rates
  • É parte de: Earth and planetary science letters, 2020-10, Vol.547, p.116441, Article 116441
  • Descrição: 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. •Paleo-erosion rates from a ∼135-m high river terrace in the Yamuna catchment.•New luminescence and surface exposure ages from the river terrace.•Aggradation occurred during marine isotope stage 2, when discharge was reduced.•Lower [10Be] in terrace sand compared to river sand can be explained by ice cover.
  • Editor: Elsevier B.V
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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