Transport-limited Erosion on the Lowlands

Vast tracts of the South American and West African lowlands have predominantly transport-limited denudation regimes (Stallard, 1988). These regions represent the flattest and youngest erosional/ depositional surfaces of the late Neogene. On the shield, the substrate is crystalline basement, while in the intracratonic basins, the Andean foreland basin, and the coastal plains, much of the sedimentary substrate consists of strongly pre-weathered fluvio-lacustrine sediment (Stallard, 1985, 1988  

Where easily weathered lithologies such as carbonates and evaporites are near the surface, such as in the lower Amazon valley, their contribution to the rivers appears minor, probably because thick residual soil covers have developed. This indicates that susceptibility to weathering is indeed less important in controlling lowland erosion rates. Carbonate platforms, such as southern Florida and the Yucatan in North America, are exceptions because of deep-water circulation throughout the carbonate karst. 

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