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<br />. <br /> <br /><< It'" f""\ <br />"l.~;j <br /> <br />gneisses, shales, sandstone, limestone, and unconsolidated <br />silts, clays, sand, and gravel. <br /> <br />The form of the Southern Rocky Mountain Physiographic Province <br />is elongate with north-south trending ranges. The ranges are <br />basically large up-warps eroded to Precambrian crystalline <br />cores and are flanked on the margins by steeply dipping <br />Hogbacks to gently dipping cuestas. For the most part, the <br />ranges are considered to be high level erosion surfaces. <br />The higher peaks (monadnocks) stand well above either a high <br />level pediment plain or low level peneplains. Both normal <br />and thrust faulting are typical throughout the Province. The <br />headwaters of the Arkansas River flow through a down-clropped <br />block or graben. <br /> <br />. <br /> <br />During the Pleistocene Epoch, the mountains were subjected <br />to glaciation with alpine glaciers repeatedly occupying and <br />sculpturing the rock. The advancing and retreating glaciers <br />left great mounds of terminal and lateral moraines and a <br />thinner cover of ground moraine. Broad flat meadows are <br />underlain by a relatively thin layer of glacial outwash. <br />Later erosion produced a variety of geomorphic features such <br />as talus slopes, alluvial fans, and terraces. <br /> <br />A noticeable geologic change occurs in the vicinity of Canon <br />City as this is the crystalline-sedimentary rock contact and <br />the boundary between the Southern Rocky Mountain Physiographic <br />Province and the Colorado Piedmont of the Great Plains <br />Physiographic Province. The plains east of Canon City <br />represent an erosional surface which contains numerous out- <br />crops of the underlying sedimentary bedrock. ~~a~ly--- <br />this portion of the Dlain~ i&-1o~d on the southern edge <br />v[ tile uenver Basin which gives the formations a general dip <br />of less than 10 degrees to the north. Exceptions to this <br />are local structures and other structures adjacent to mountain <br />fronts where the sediments are sharply upturned on the moun- <br />tain flanks. <br /> <br />b. Sites Geology <br /> <br />, <br /> <br />Ruedi Dam and Reservoir are located on Palezoic sediments <br />which flank the crystalline Sawatch Range. Regional dip is <br />to the west; however, local structures vary from this. Ruedi <br />Dam is constructed on the Permian-Pennsylvanian Maroon forma- <br />tion, which at the site is a red, poorly sorted sandstone <br />dipping to the west at .approximately 30-35 degrees. <br /> <br />. <br /> <br />rU-l2 <br />