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<br />1 <br /> <br />1 <br />1 <br /> <br />1 <br />1 <br /> <br /> <br /> <br />lJ <br /> <br /> <br />1 <br /> <br />axis that is subparallel to the mountain front and about 10 to 30 <br />miles east of it. The proximity of the axis to the mountains <br />results in a steep western limb and a gently sloped eastern limb. <br />The Foothills Belt is a transitional area about five to 10 <br />miles wide between these two major physiographic provinces. The <br />sedimentary beds adjacent to the Precambrian mountain front are <br />steeply dippling and occasionally overturned. The dip <br />progressively decreases in the younger formations as they outcrop <br />at greater distances from the mountain front. Between Lyons and <br />the northern Colorado border a series of Northwest-tending high- <br />angle bedrock faults offset the sedimentary beds. Draping of <br />sediments over these faults produces a series of en-echelon folds <br />and faults. Taken together, these intermediate-scale structure <br />deformations, regional deformations produced by the Front Range and <br />the Denver Basin, and more localized small-scale folding and <br />faulting, result in a generally complex geologic setting throughout <br />the Foothills Belt. <br />4.2 Local Stratigraphy <br />The important formations in this area are all upper Cretaceous <br />in age and are limited to the middle of the regional stratigraphic <br />column. They include the Dakota Group, the Ft. Benton Formation, <br />the Niobrara Formation and the Pierre Shale. The general <br />stratigraphic descriptions in this section are summarized from <br />three graduate theses that contained detailed lithologic <br />descriptions compiled during field mapping and section measurement <br />activities (Hunter; 1947, Masters, 1957). These documents provide <br />the best available specific lithologic information on Dowe Flats. <br />The most important stratigraphic unit in Dowe Flats are, from <br />oldest to youngest, the Dakota Group, containing the Lytle and <br />South Platte formations; the Ft. Benton Formation, the Niobrara <br />95 <br /> <br />