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<br /> <br />All the other materials in the bottom 200 feet of the Smoky Hill <br />Member are dark gray to black, pyritiferous, cancerous, marine <br />' shales. A second 20-foot thick limestone bed was mapped at Dowe <br />Flats and measured in the Little Thompson outcrop at the interval <br />' from 200 to approximately 220 <br />A fi <br />l li <br />t <br />b <br />d <br />h <br />i feet above the <br />b <br />25 bottom of Smoky Hill. <br />h <br />k <br /> na <br />mes <br />one <br />e <br />, w <br />t <br />a ase about <br />6 e Smo <br />y <br />feet above t <br /> Hill Member, was also located in both field efforts; however, its <br />' k <br /> thic <br />ness was measured as 12 feet by Mailed (1962) and 93 feet by <br />Quam (1932). Based upon interpretation of geophysical logs form <br />t oil exploration wells drilled 10 to 15 miles south and east of the <br />site (Lowman 1977), the 93 foot value appears to be more realistic. <br />The fact that the limestones in the Smoky Hill Member are not <br />discussed in regional geologic summary papers indicates that hey <br />are local in nature and probably disappear to the north and south. <br />The lower Pierre Shale is the uppermost unit considered in <br />this report. Only the lower 500 feet of the Pierre Shale are found <br />in Dowe Flats; the remainder has been eroded away. The lower <br />' portions of Pierre Shale are homogeneous dark brown to gray-black <br />marine shale that weathers to a buff color. The basal portion of <br />' the Pierre Shale, immediately above the Niobrara Formation, is <br />sandy, but he sand content decreases in the main portion of the <br />' shale. <br />' 9.3 Local Structure <br />The area surrounding Dowe Flats is structurally complex with <br />several types of structure features of differing scales overprinted <br />upon each other. Despite detailed studies, interpretations, and <br />reinterpretations, the origin and exact relationship between all of <br />' the structure features remains unclear. <br />The regional Dakota hogback that parallels the eastern side of <br />' the Front Range through central and northern Colorado forms the <br />48 <br />1 <br />