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confluence with the South Platte River, <br />9• The basin slopes to the east from an elevation of 1+,260 feet <br />m.s.l., at Mount Evans to approximately 5,300 feet, m.s.l., at the mouth <br />of Bear. Creek. The slope of the tributary streams rising in the mountains <br />usually exceeds 200 feet per mile, while slopes in excess of 500 feet per <br />mile are common. Sufficient topographic data are not at hand to permit <br />plotting an accurate stream profile. From data available, the average <br />slope of Bear Creek from its source to Evergreen appears to be about 230 <br />feet per mile, from Evergreen to Idledale about 110 feet per mile, from <br />Idledale to Morrison approximately 200 feet per mile, while from Morrison <br />to the mouth the slope is about 45 feet per mile. <br />1.0. Geology. -- The eastern tip of the Bear Creek Basin is on the <br />extreme western edge of what is known as the Colorado Piedmont, a late <br />mature to old elevated plain, of the Great Plains Province. The remainder <br />of the basin is in the Georgetown District of the Southern RockyMountain <br />Province, and is crossed by that range of mountains known as the Colorado <br />Front Range, The basin, exclusive of the eastern tip, consists of pre- - <br />Cambrian granite and gneiss, the latter being penetrated by a great number <br />of dikes, principally of pegmatite and diorite. Along the eastern edge of <br />the gneiss, a portion of the strata was strongly affected by a great uplift <br />in post - Cretaceous times. Then the mountains were, in a large part, <br />peneplained., with the result that the sharply dipping formations of <br />Carboniferous, Jurassic, and Cretaceous periods rise to the surface as <br />hogback ridges. The eastern tip of the basin is comprised of flat - -lying <br />deposits of the Tertiary age known as the Denver formation. Alpine glaci- <br />ation occurred in the western portion of the basin during the Pleistocene <br />age. <br />11, Minerals.- Coal is the only mineral of importance found within <br />the Bear Creek Basin. The coal beds which occur in the lower part of the <br />Laramie formation are found, chiefly, in that part of the basin that lies <br />I.W <br />