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<br />35 <br /> <br />by gravity-induced slope failure (Fig. 5.6). At other localities, <br /> <br />...... <br />W <br />00 <br />0) <br /> <br />soil had slumped into channels as the result of disturbance by live- <br /> <br />stock, with cattle being the most destructive. After the August 15 <br /> <br />storm, some of the steepest slopes had lost nearly all of their soil <br /> <br />cover (Fig. 5.7). <br /> <br />Considering the above observations and studies, it appears <br /> <br />that no single erosional process is dominant. In upper portions of <br /> <br />basins, sediment is derived through the process of rill development <br /> <br />and from removal of sediment accumulated in channels as the result <br /> <br />of soil creep. In lower portions of basins, sediment is derived <br /> <br />from the removal of sediment accumulated in channels due to soil <br /> <br />creep and from bank failures of incised alluvial fill. Consequently, <br /> <br />all portions of the basins are undergoing active erosion. <br /> <br />5.2.5 <br /> <br />Soils <br /> <br />Soil depth studies were conducted in six of the eight <br /> <br />basins with the goal of finding inter- and intrabasin relationships. <br /> <br />Soil depth is the thickness of the layer of residual material derived <br /> <br />from underlying weather, yet structurally distinct, bedrock <br /> <br />(Appendix) . <br /> <br />The soils are derived from two lithologies in the Mancos Shale: <br /> <br />shale and sandstone. Field observations indicate that portions 'of <br /> <br />the badlands are underlain predominantly by shale, of which Basins <br /> <br />A, N, and Q are examples. The remainder of the badlands are <br /> <br />underlain by interbedded shale and sandstone, of which Basins S, T, <br /> <br />and U are examples. Soil texture analyses by Lusby, et al. (1963) <br /> <br />show that soils derived from shales are clay-rich, while soils derived <br />from interbedded shale and sandstone are mixtures of clay and sand. <br />