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www.solid-earth-discuss.net/3/541/2011/
doi:10.5194/sed-3-541-2011
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Erosion rates deduced from Seasonal mass balance along an active braided river in Tianshan
1Institut de physique du globe de Paris – Sorbonne Paris Cité, Université Paris Diderot, CNRS, UMR7154, 1 rue Jussieu, 75238 Paris Cedex 05, France
2Key Laboratory of Water Environment and Resource, Tianjin Normal University, 393 Binshui west road, Tianjin 300387, China
3The States Key laboratory of Cryospheric Science, Cold and Arid Region Environmental and Engineering and Research Institute, Chinese Academy of Sciences 260 Donggang west road, Lanzhou, China
4Département de Géologie, UMR8538, CNRS, Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris, France
Abstract. We report measurements performed during two complete flow seasons on the Urumqi River, a proglacial mountain stream in the northeastern ank of the Tianshan, an active mountain range in Central Asia. This survey of flow dynamics and sediment transport (dissolved, suspended and bed loads), together with a 25-year record of daily discharge, enables the assessment of secular denudation rates on this high mountain catchment of Central Asia. Our results show that chemical weathering accounts for more than one third of the total denudation rate. Sediment transported as bed load cannot be neglected in the balance given that sand and gravel transport accounts for one third of the solid load of the river. Overall, the mean denudation rates are low, averaging 46 t × km−2 × yr−1 (17–18 m Myr−1). We furthermore analyse the hydrologic record to show that the long-term sediment budget is not dominated by extreme and rare events but by the total amount of rainfall or annual runoff. The rates we obtain are in agreement with rates obtained from the mass balance reconstruction of the Plio-Quaternary gravely deposits of the foreland but signicantly lower than the rates recently obtained from cosmogenic dating of river sand. We show that the resolution of this incompatibility has an important consequence for our understanding of the interplay between erosion and tectonics in the semi-humid ranges of Central Asia.
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Notice on Discussion StatusCitation: Liu, Y., Métivier, F., Gaillardet, J., Ye, B., Meunier, P., Narteau, C., Lajeunesse, E., Han, T., and Malverti, L.: Erosion rates deduced from Seasonal mass balance along an active braided river in Tianshan, Solid Earth Discuss., 3, 541-589, doi:10.5194/sed-3-541-2011, 2011. Bibtex EndNote Reference Manager XML
