Title
Sediment production and delivery in the Amazon River basin quantified by in situ-produced cosmogenic nuclides and recent river loads
Date Issued
01 May 2011
Access level
metadata only access
Resource Type
journal article
Author(s)
Wittmann H.
von Blanckenburg F.
Maurice L.
Filizola N.
Kubik P.W.
Institut de recherche pour le développement
Abstract
We use cosmogenic nuclide-derived denudation rates from in situ-produced 10Be in river sediment to determine sediment production rates for the central Amazon River and its major tributaries. Recent developments have shown that this method allows calculating denudation rates in large depositional basins despite intermediate sediment storage, with the result that fluxes of the sediment-producing hinterland can now be linked to those discharged at the basins' outlet. In rivers of the central Amazonian plain, sediment of finer grain sizes (125-500 μm) yields a weighted cosmogenic nuclide-derived denudation rate of 0.24 ± 0.02 mm/yr that is comparable to the integrated rate of all main Andean-draining rivers (0.37 ± 0.06 mm/yr), which are the Beni, Napo, Mamoré, Ucayali, and Marañón rivers. Coarser-grained sediment (>500 μm) of central Amazonian rivers is indicative of a source from the tectonically stable cratonic headwaters of the Guyana and Brazilian shields, for which the denudation rate is 0.01-0.02 mm/yr. Respective sediment loads can be calculated by converting these cosmogenic nuclide-derived rates using their sediment-producing areas. For the Amazon River at Óbidos, a sediment production rate of ~610 Mt/yr results; non-Andean source areas contribute only ~45 Mt/yr. A comparison with published modern sediment fluxes shows similarities within a factor of ~2 with an average gauging-derived sediment load of ~1000 Mt/yr at Óbidos, for example. We attribute this similar trend in cosmogenic versus modern sediment loads first to the absence of long-term deposition within the basin and second to the buffering capability of the large Amazon floodplain. The buffering capability dampens short-term, high-amplitude fluctuations (climatic variability in source areas and anthropogenic soil erosion) by the time the denudation rate signal of the hinterland is transmitted to the outlet of the basin. © 2011 Geological Society of America.
Start page
934
End page
950
Volume
123
Issue
5
Language
English
OCDE Knowledge area
Geología Mineralogía Oceanografía, Hidrología, Recursos hídricos
Scopus EID
2-s2.0-79953788910
Source
Bulletin of the Geological Society of America
ISSN of the container
00167606
Sources of information: Directorio de Producción Científica Scopus