A Rouse-based method to integrate the chemical composition of river sediments: Application to the Ganga basin | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  A Rouse-based method to integrate the chemical composition of river sediments: Application to the Ganga basin

Type de publication:

Journal Article

Source:

Journal of Geophysical Research-Earth Surface, Volume 116 (2011)

ISBN:

0148-0227

URL:

http://onlinelibrary.wiley.com/doi/10.1029/2010JF001947/abstract

Mots-clés:

UMR 7154 ; Géochimie et cosmochimie ; Composition of the continental crust ; Floodplain dynamics ; Geochemical modeling ; Hydrology and fluvial processes ; Major and trace element geochemistry

Résumé:

<p>[1] The Ganga River is one of the main conveyors of sediments produced by Himalayan erosion. Determining the flux of elements transported through the system is essential to understand the dynamics of the basin. This is hampered by the chemical heterogeneity of sediments observed both in the water column and under variable hydrodynamic conditions. Using Acoustic Doppler Current Profiler (ADCP) acquisitions with sediment depth profile sampling of the Ganga in Bangladesh we build a simple model to derive the annual flux and grain size distributions of the sediments. The model shows that ca. 390 (±30) Mt of sediments are transported on average each year through the Ganga at Haring Bridge (Bangladesh). Modeled average sediment grain size parameters D50 and D84 are 27 (±4) and 123 (±9) μm, respectively. Grain size parameters are used to infer average chemical compositions of the sediments owing to a strong grain size chemical composition relation. The integrated sediment flux is characterized by low Al/Si and Fe/Si ratios that are close to those inferred for the Himalayan crust. This implies that only limited sequestration occurs in the Gangetic floodplain. The stored sediment flux is estimated to c.a. 10% of the initial Himalayan sediment flux by geochemical mass balance. The associated, globally averaged sedimentation rates in the floodplain are found to be ca. 0.08 mm/yr and yield average Himalayan erosion rate of ca. 0.9 mm/yr. This study stresses the need to carefully address the average composition of river sediments before solving large-scale geochemical budgets.</p>

Notes:

Times Cited: 14 Mugnier, Jean-Louis/E-7241-2011; galy, valier/I-6185-2012; Gaillardet, Jerome/F-9096-2010 Gaillardet, Jerome/0000-0001-7982-1159 15