River chemistry, geology, geomorphology, and soils in the Amazon and Orinoco basins.

Abstract

To a first order, erosion processes are seen to occupy a continuum between weathering-limited (steep slopes, thin soils) and transport-limited (slight slopes, thick soils). Denudation rates for the former are lithology dependent, and significant removal of cation-rich, unstable, solid phases is expected. For the latter, erosion rates should depend on the regional lowering of the landscape; lithologic susceptibility to weathering should be a minor factor. The compositional trends of river dissolved and solid load can be approximated for different weathering regimes using soil chemistry data. -from Author