Abstract

Chemical weathering influences the detrital composition of sand-size sediment derived from source areas subject to different amounts of precipitation in the Coweeta Basin, North Carolina. Of the grain types studied, rock fragments are most sensitive to chemical degradation; therefore, their abundance is the best indicator of cumulative weathering effects. Destruction of sand-size rock fragments by chemical weathering is a function of both the intensity and duration of chemical weathering experienced by grains in regoliths of the source area. In the Coweeta Basin, the intensity of chemical weathering is directly related to the climate via effective precipitation in individual subbasins, whereas the duration of chemical weathering is inversely related to the relief ratio of the watershed. Therefore, soils in watersheds with low-relief ratios and high discharge per unit area experience the most extensive chemical weathering, and sediments derived from these watersheds contain the lowest percentage of rock fragments. The effects of climate alone cannot explain the systematic variation of rock fragment abundance in sediments from the Coweeta Basin. The compositional imprint left on these sediments by chemical weathering is a function of both climate and topographic slope in the sediment source area.

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