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<br />( ..' 1 ~.-: t '. ," <br /> <br />Geoloov and Phvsiooraohic Descriotionll <br /> <br />Highline Breaks watershed is located within the Colorado Piedmont section of the <br /> <br /> <br />Great Plains Physiographic Province (Fenneman, 1931). The Colorado Piedmont <br /> <br /> <br />represents an old erosion surface. It is a mature to old, broadly rolling, elevated plain <br /> <br /> <br />with local scarps. <br /> <br />Bedrock consists primarily of Cretaceous marine shales and limestones. These <br /> <br />formations dip slightly to the northwest, toward'the Denver structural basin. The <br /> <br />oldest formation that crops out in the watershed is the Upper Cretaceous Carlile <br /> <br />shale, which is found south of the Arkansas River at La Junta. Overlying the Carlile <br /> <br />Shale ffrom oldest to youngestt is the Fort Hays limestone and Smokey Hill shale <br /> <br />members of the Niobrara FormationT and the Pierre shale. <br /> <br />Shales and limestones have higher concentration of some minerals than other rock <br /> <br /> <br />types~. This is particularly true of minerals such as sulfur and trace minerals <br /> <br /> <br />such as arsenic, boron, and selenium (Turekina and Wedepohl, 1961). <br /> <br />Studies by Schultz and others (1980) also showed elevated sulfur and trace mineral <br /> <br />concentrations in studies done of the Upper Cretaceous Pierre shale and equivalent <br /> <br />formations. The sediment source areas for these formations was to the west. The <br /> <br />watershed area is far from the source area, so sediments in this area are almost <br /> <br />2a*5 <br />