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- 5 - ~, ~ ~ Cherry Creek channel gradients are approximately as fcllows: frcr~ the lower end of the ',atershed upstream to the canyon section near FranktoWTI, 2S to 3S feet per mile; through the canyon reach, 35 to 130 feet per mile; and from the qanyon section upstream along the major upper tributary streans, 3S to 60 feet per mile. Other tributary channels range in slope from about 3S feet per mile along lower reaches to ZOO feet per mile along upper reaches. J. I I . Geology.- The bedrock formations which crop out in the Frankto,,~- Parker Watershed are of Upper Cretaceous age or younger. The structure of the formations is simple with the strata generally having a very gentle dip in a northeasterly direction. The principal bedrock forrrrations are the Denver forraation of Upper Cretaceous and Early Paleocene age, the Dawson arkose of Late Paleocene and Early Eocene age, and the Castle Rock conglomerate of Lower Oligocene age. I: , . . The Denver formation consists of crab-colored andesitic sandstone, siltstone, sandy shale, and some clay shale and conglomerate. The Dawson arkose consists mainly of light-colored, loosely cemented, arkosic sandstone with some thin beds of greenish clay and shale. A bed of reddish clay lies near the base. This bed is being quarried for refractory clay at several places within the watershed. The Castle Rock conglomerate is a hard coarse-grained conglomeratic arkose. Hear the contact of the Dawson and the Castle Rock, thin hard volcanic beds consisting of pink to gray rhyolite and welded tuff are present in &"all localized areas. These volcanic rocks are being quarried for building stone and riprap at a few localities along the west side of the watershed. I ~. I ~ Outcrops of the Denver formation occur only in a relatively small area along the valley of Cherry Creek from the lower end of the watershed south to the vicinity of Parker, Colorado. The Dawson arkose is present from this point southward to the upper end of the watershed and underlies the major portion of the watershed area. The Castle Rock conglomerate and the volcanic rocks cap the mesas and buttes in a mnall area in the central part of the watershed. Unconsolidated sand and gravel deposits of Pleistocene age occur in terraces along the larger stream valleys. Thin alluvial deposits of Recent age mantle the lower terraces and. valley bottoms. Thin eolian deposits consisting of silt, clay, and fine sand are widespread in the upper area. Much cf the upland area in the lower watershed is mantled v,i th some'-Ihat thicker eolian rlepo"i t", cons; at; ng mainly of fine sand and some silt and clay.