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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union
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Volume 6, issue 3
Earth Surf. Dynam., 6, 611-635, 2018
https://doi.org/10.5194/esurf-6-611-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Earth Surf. Dynam., 6, 611-635, 2018
https://doi.org/10.5194/esurf-6-611-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 27 Jul 2018

Research article | 27 Jul 2018

Temporal variability in detrital 10Be concentrations in a large Himalayan catchment

Elizabeth H. Dingle1, Hugh D. Sinclair1, Mikaël Attal1, Ángel Rodés2, and Vimal Singh3 Elizabeth H. Dingle et al.
  • 1School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, UK
  • 2Scottish Universities Environmental Research Centre (SUERC), Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride, G75 0QF, UK
  • 3Department of Geology, University of Delhi, Delhi 110007, India
  • * Invited contribution by Elizabeth H. Dingle, recipient of the EGU Geomorphology Outstanding Student Poster and PICO Award 2017.

Abstract. Accurately quantifying sediment fluxes in large rivers draining tectonically active landscapes is complicated by the stochastic nature of sediment inputs. Cosmogenic 10Be concentrations measured in modern river sands have been used to estimate 102- to 104-year sediment fluxes in these types of catchments, where upstream drainage areas are often in excess of 10000km2. It is commonly assumed that within large catchments, the effects of stochastic sediment inputs are buffered such that 10Be concentrations at the catchment outlet are relatively stable in time. We present 18 new 10Be concentrations of modern river and dated Holocene terrace and floodplain deposits from the Ganga River near to the Himalayan mountain front (or outlet). We demonstrate that 10Be concentrations measured in modern Ganga River sediments display a notable degree of variability, with concentrations ranging between  ∼ 9000 and 19000atomsg−1. We propose that this observed variability is driven by two factors. Firstly, by the nature of stochastic inputs of sediment (e.g. the dominant erosional process, surface production rates, depth of landsliding, degree of mixing) and, secondly, by the evacuation timescale of individual sediment deposits which buffer their impact on catchment-averaged concentrations. Despite intensification of the Indian Summer Monsoon and subsequent doubling of sediment delivery to the Bay of Bengal between  ∼ 11 and 7ka, we also find that Holocene sediment 10Be concentrations documented at the Ganga outlet have remained within the variability of modern river concentrations. We demonstrate that, in certain systems, sediment flux cannot be simply approximated by converting detrital concentration into mean erosion rates and multiplying by catchment area as it is possible to generate larger volumetric sediment fluxes whilst maintaining comparable average 10Be concentrations.

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We present 18 new cosmogenic radionuclide samples collected from modern river sand and dated Holocene terrace and floodplain deposits from the Ganga River at the Himalayan mountain front, which display a notable degree of temporal variability. This variability is explored using field observations and numerical and statistical analysis. We propose that the observed variability is driven by the nature of stochastic inputs of sediment and the evacuation timescales of individual sediment deposits.
We present 18 new cosmogenic radionuclide samples collected from modern river sand and dated...
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