Two prominent hypotheses have been offered on the relationship oftecton-ics to chemical weathering intensity and long-term climate regulation. Some researchers have presented evidence, mainly from the Amazon and Congo River watersheds, that there is a strong relief effect on weathering rates; high relief is correlative with high denudation rates, whereas the lowest rates occur in the flat lowlands (Stallard 1995a, 1995b; Edmond et al. 1995; Gaillar-det et al. 1995). These authors distinguish between weathering and transport-limited erosional regimes. For the former, the rate of transport exceeds the rate of chemical weathering (high slopes), whereas for the latter the reverse is true, so thick soils develop with low denudation rates.
The other main hypothesis is centered on the increase in mechanical erosion and hence chemical erosion driven by uplift, an idea apparently first suggested by T. C. Chamberlain (1899; see Raymo 1991) as an explanation of the initiation of the ice ages. These proposals will be examined more closely in the following discussion, also touching on related issues regarding the interrelation of rock chemistry and tectonics to the carbon sink with respect to the atmosphere/ocean system.
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