Erosion rates on different timescales derived from cosmogenic 10Be and river loads: implications for landscape evolution in the Rhenish Massif, Germany |
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| Authors: | H Meyer R Hetzel H Strauss |
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| Institution: | 1. Geologisch-Pal?ontologisches Institut, Westf?lische Wilhelms-Universit?t M??nster, Corrensstr. 24, 48149, M??nster, Germany
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| Abstract: | We determined erosion rates on timescales of 101–104 years for two catchments in the northeastern Rhenish Massif, in order to unravel the Quaternary landscape evolution in a
Variscan mountain range typical of central Europe. Spatially averaged erosion rates derived from in situ produced 10Be concentrations in stream sediment of the Aabach and M?hne watersheds range from 47 ± 6 to 65 ± 14 mm/ka and integrate over
the last 9–13 ka. These erosion rates are similar to local rates of river incision and rock uplift in the Quaternary and to
average denudation rates since the Mesozoic derived from fission track data. This suggests that rock uplift is balanced by
denudation, i.e., the landscape is in a steady state. Short-term erosion rates were derived from suspended and dissolved river
loads subsequent to (1) correcting for atmospheric and anthropogenic inputs, (2) establishing calibration curves that relate
the amount of suspended load to discharge, and (3) estimating the amount of bedload. The resulting solid mass fluxes (suspended
and bedload) agree with those derived from the sediment volume trapped in three reservoirs. However, resulting geogenic short-term
erosion rates range from 9 to 25 mm/ka and are only about one-third of the rates derived from 10Be. Model simulations in combination with published sediment yield data suggest that this discrepancy is caused by at least
three factors: (1) phases with higher precipitation and/or lower evapotranspiration, (2) rare flood events not captured in
the short-term records, and (3) prolonged periods of climatic deterioration with increased erosion and sediment transport
on hillslopes. |
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