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I I I I I I I I I I I I I I I I I I I '})l 144 grain sizes. of colluvium accumulation unstratified, slopes. The upper portions of slopes generally have only a thin veneer covering bedrock. Colluvium is mapped only where its is thi ck enough to fonn a di sti nct 1 andfonn, usually unconsoli dated, wedge-shaped deposi ts on the lower porti ons of Thicknesses of mapped colluvium range greatly, depending on slope' angle, proximity of a stream to the base of a slope, and the competence of the bedrock source. In areas where slopes are gentle and the rock fonnations are easily eroded, maximum thicknesses appear to be as great as 75 to 100 feet. In areas where exposures of resi stant rock fonn a hi gh angl e slope faci ng toward a stream fl owi ng along the base of the slope; maximum thicknesses appear to be only five to ten feet. Landslide Deposits (Qls) Extensive 1 andsl ide deposi ts occur along the 1 eft si de of the ri ver in the upper canyon section in the vicinity of Warner Point. No in-place bedrock was mapped in this area, and the, terrain is characterized. by a hummocky appearance. There is no indication of recent movement of these slides. Massive slumping is also evident upstream where sound Tertiary basalt flows overlie weak sedimentary rocks. Recent landslide activity can also be seen in the lower part of the study area downstream of Powell Park; There, occasional massive toppling has occurred as the weathering of weak shale beds has undennined overlying sandstone layers, releasing large blocks to slide down the slopes. Alluvial Deposts (Qa) In modern stream drainages, including the White River, interbedded gravel, sand, and silt fonn unconsolidated deposits in both active channels and small floodplains. 4-7