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SEDIMENT BUDGETS IN CATCHMENT–ALLUVIAL FAN SYSTEMS OF THE NORTHERN TIAN SHAN (CHINA): IMPLICATIONS FOR MASS-BALANCE ESTIMATES, DENUDATION AND SEDIMENTATION RATES IN OROGENIC SYSTEMS

Abstract : Mass balances are often used to calculate sediment fluxes in sedimentary basins and denudation rates in adjacent topographies on intermediate to long timescales (from a few tens of thousand to a million years). In this study, we focus on simple Quaternary catchment–alluvial fan systems in the northern Tian Shan Range and its foreland basin to discuss some ideas about sediment production, storage, release, and bypass in relatively short (100 km long) sediment routing systems. Based on a geometrical reconstruction of the fans, we estimated the volumes of sediments exported out of the range and deposited in its alluvial piedmont during the Middle-Late Pleistocene and the Holocene. This work shows that the two areas clearly present evidence of a temporary but significant storage of sediments during the Pleistocene. These sediments were then excavated and delivered farther into the foreland basin during the Holocene. The difference between the volumes of materials released from the range and piedmont areas and the volume stored in the contemporaneous fans downstream indicates that the latter did not trap the whole sediment load transported by the rivers. The alluvial fans were bypassed by 27 to 78% of this load toward the downstream alluvial plain. It implies a major volumetric partitioning of the deposits between the fans and the alluvial plain, with a sedimentation rate about twenty times higher in the fans than in the plain. However, this volumetric partitioning might only occur during periods with a very specific hydrological regime such as the Holocene deglaciation. Eventually, the peculiar sediment storage and release pattern within the range and piedmont areas during the Pleistocene and Holocene complicates the calculation of mean paleodenudation rates using either sediment budgets or in situ produced cosmogenic nuclides.
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https://hal-insu.archives-ouvertes.fr/insu-01406440
Contributor : Isabelle Dubigeon <>
Submitted on : Thursday, December 1, 2016 - 11:02:37 AM
Last modification on : Saturday, March 28, 2020 - 2:04:56 AM

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  • HAL Id : insu-01406440, version 1

Citation

Laurie Barrier, Laure Guerit, Marc Jolivet, Stephane Dominguez, François Métivier, et al.. SEDIMENT BUDGETS IN CATCHMENT–ALLUVIAL FAN SYSTEMS OF THE NORTHERN TIAN SHAN (CHINA): IMPLICATIONS FOR MASS-BALANCE ESTIMATES, DENUDATION AND SEDIMENTATION RATES IN OROGENIC SYSTEMS. Source to Sink: a long term perspective of sediment budgets and sources characterization, Géosciences-Rennes, Nov 2016, Rennes, France. pp.37. ⟨insu-01406440⟩

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