Erosion bedrock

Fig. 9-3 Conceptual model to describe the interaction between chemical weathering of bedrock and down-slope transport of solid erosion products. It is assumed that chemical weathering is required to generate loose solid erosion products of the bedrock. Solid curve portrays a hypothetical relationship between soil thickness and rate of chemical weathering of bedrock. Dotted lines correspond to different potential transport capacities. Low potential transport capacity is expected on a flat terrain, whereas high transport is expected on steep terrain. For moderate capacity, C and F are equilibrium points. (Modified with permission from R. F. Stallard, River chemistry, geology, geomorphology, and soils in the Amazon and Orinoco basins. In J. I. Drever, ed. (1985), "The Chemistry of Weathering," D. Reidel Publishing Co., Dordrecht, The Netherlands.)...

Fig. 9-8 Histogram of dissolved solids of samples from the Orinoco and Amazon River basins and corresponding denudation rates for morpho-tectonic regions in the humid tropics of South America (Stal-lard, 1985). The approximate denudation scale is calculated as the product of dissolved solids concentrations, mean armual runoff (1 m/yr), and a correction factor to account for large ratios of suspended load in rivers that drain mountain belts and for the greater than average annual precipitation in the lowlands close to the equator. The correction factor was treated as a linear function of dissolved solids and ranged from 2 for the most dilute rivers (dissolved solids less than lOmg/L) to 4 for the most concentrated rivers (dissolved solids more than 1000 mg/L). Bedrock density is assumed to be 2.65 g/cm. (Reproduced with permission from R. F. Stallard (1988). Weathering and erosion in the humid tropics. In A. Lerman and M. Meybeck, Physical and Chemical Weathering in Geochemical Cycles," pp. 225-246, Kluwer Academic Publishers, Dordrecht, The Netherlands.)...

In regions where the erosion regime is weathering limited, susceptibility of the bedrock to chemical and physical weathering controls erosion rates. This susceptibility relates directly to the chemical and physical properties of the rock. Susceptibility also depends on local climate. Moreover, weathering rates are affected by the... 

Detritus from a paleolandscape contains information on the paleorelief (in fact, the paleohypsometry), of its former catchment, through its probability distribution of cooling ages, provided the paleoerosion rate can be estimated, and some assumption about the spatial uniformity of erosion (and bedrock abundance of the thermochronometric mineral) can be made. The former could potentially be estimated from mineral-pair methods, such as using coupled apatite He and apatite FT ages from the same clast, or from AERs of bedrock samples that record the erosion rate through the time interval in question. In general, the latter constraint must be assumed, however. 

Stuart, 2002). A relatively recent development has been the use of thermochronologic data for modem stream sediment samples to hmit the bedrock cooling age distribution and relief (Stock and Montgomery, 1996) or average erosion rate (Brewer, 2001 Bullener al., 2001) for the stream s catchment. Such studies may yield a sense of how rehef developed over time within specific catchments, and catchment-to-catchment variations may, in turn, reveal the nature of topographic change over time. 

Figure 6 Glacial chemical-erosion rates, as measured by the cationic fluxes, for a range of glaciers worldwide as a function of specific annual runoff. Higher cationic fluxes for a given specific runoff are associated with carbonate/carbonate-rich (C-rich) and basaltic bedrock lithologies. Lower fluxes are associated with other sedimentary (sed) and plutonic/metamorphic bedrocks (Pl/m) (after Hodson et aL, 2000) (reproduced by permission of John Wiley Sons from Earth Surf.

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