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<br /> <br />. <br /> <br />chare.ct~riz~d ~y sharp topographic!l.l relief resUltingfrQlllthe. <br />presence of 0 a veir resistanj; rock layer, j;he Castle !tock, <br />congloDlera;t;e. Canyon walls and mesa fronts, 200 to 400 feet <br />high, are common in this belt.. Cherry Creek and some of its <br />tributarie.s have cut narrow canyons through this belt. In the <br />reach from near Franktown to .nearJ>arker, Cherry Creek cou,rses <br />through a broad valley bordered :by steep to rolJ,ing ridges and. <br />hills. . Downstream from Parker, the, uplands become less r.oU€lh . <br />and the basin lies in a roJ,ling plains.area. The basin slopes. <br />northward from elevations Of. a~out 7700 feet at the 'source of <br />Cherry Cr.eek to about 5170 feet at. the confluence with the <br />South Platte River. The geological structure of the basin <br />consists of strata of upper Cretaceous age or younger, generally <br />having a very gentle dip in a northeasterly direction away from <br />the mountains. The Dawson arkose underlies the basin upstream <br />from Parker. J;t consists mai~y of light-colored loosely- <br />cemented arkosic sandstone. The Castle Rock conglomerate is a <br />hard coarse-grained conglomeratic arkose. Near the contact of <br />the Dawson arkose and the Castle Rock conglomerate are found the <br />only igneous rocks in the basin, consisting of thin hard beds <br />of pink to gray rhyolite and welded tuff in localized areas. The <br />Castle Rock conglomerate and the volcanic rocks cap the mesa.s and <br />buttes in the belt across the central basin. Much of the upland <br />area is mantled with somewhat thicker eolian deposits consisting <br />mainly of fine sand and some silt and clay. The soils are (lerived <br />principally from the Dawson and Denver fomations. The stream,. <br />bed soils are dark grayish-brown sandy loams and clay loams with <br />sandy loam to clay loam subsoil. The high plains soils. are <br />grayish-brown sandy loam to clay loam underlain by sandy loams <br />to clays. The Denver formation predominates from Parker to the <br />mouth of Cherry Creek. It is composed of drab-colored andesitic <br />sandstone, siltstone, sandy shale,and some clay shale and <br />conglomerate. Unconsolidated sand and gravel. deposits of Pleistocene <br />age occur in terraces along the larger stream valleys.. Thin alluvial <br />deposits of Recent age mantle the lower terraces and valley bottoms, <br />and thin eolian deposits of silt,.clay, .and fine sand are wid~spread <br />in the upper area. Rough broken lands and sandy or gravelly forest <br />soils, comprising about 40 percent of the basin area upstream from <br />Parker, are characterized by cover of less than 2 feet, with <br />numerous rock outcrops. <br /> <br />6. STREAM CHARACTERISTICS <br /> <br />a. Sand Creek basin.. The stream valleys in the Sand. Creek <br />basin upstream from Buckley Field are ,narrow and steep-sided, <br />averaging one-fourth mile wide or less. From Buckley Field <br /> <br />6 <br /> <br />. <br />