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• <br />' Grand Junction Pipe <br />Surficial Geology Investigation <br />April 5, 2001 <br />Proposed South Fruits Gravel Pit Extension, Fruits, Colorado <br />Page 2 <br />' 3. WHITNEY, J.W., 1981, Surficial Geologic Map of the Grand Junction Quadrangle, Colorado and Utah, U.S.G.S. Misc. <br />Geol. Invest., Map I-1289. <br />' 4. LOHMAN, S.W., 1963, Geologic Map of the Grand Junction Area, Colorado, U.S.G.S. Misc. Geol, Invest., Map I-40d <br />5. LOHMAN, S.W., 1965, Geologic and Artesian Water Supply, Grand Junction Area, Colorado, Prof. Paper 451, 149 p. <br />6. SCHWOCHOW, S.D., 1978, Mineral Resources Survey of Mesa County, Colo. Geol. Survey Resource Series 2, 109 p. <br />' The general geology of this area wnsists of a thick series of gently dipping (4 to 8 degrees to the northeast) sedimentary beds, <br />covered with thin deposits of unconsolidated alluvial coarse grained and fine grained soils. This tract is believed to be <br />underlain by the Dakota Formation, which does not outcrop on this site. <br />' This tract is located approximately 2 miles northeast of the steep slopes and cliffs ofthe Colorado National Monument. The <br />Colorado National Monument is at the northeast portion of the Uncompahgre Uplift and the steep cliffs overlooking the <br />' Redlands and Colorado River are the surface expression of the Redland Fault Complex. The higher elevations of the <br />Colorado National Monument represent a vertical displacement in excess of 2000 feet. <br />' The site is located on the north, northeastern flank of the Uncompahgre Uplift, with the sedimentary beds dipping into the <br />Piceance Basin, to the north northeast. The structurnl geology on this particular site is rehrtvely uncomplicated, with the <br />site being located approximately 2 miles northeast of the Redlands Fault Complex and is at the southeast margin of the <br />Piceance Basin. Some minor faulting is located near the Colorado/Utah State Line, approximately 25 miles northwest of <br />' this site. This faulting is associated with several small, mapped anticline swctures. The structural geology on this particular <br />site is relatively uncomplicated. <br />SJTE GEOLOGY <br />' The trail is located within the geologically active flood plain of the Colorado River. This active flood plain is composed of <br />approximately 15 to 25 feet of unconsolidated soils which are underlain by a very thick sequence of sedimentary rocks. <br />' The Dakota Formation is believed to be the `bedrock' beneath this site but, does not outcrop on the north side of the Colorado <br />River in the Fruita Area. The Dakota Formation is part of a thick sequence of sedimentary rocks which gently dip or sbpe <br />toward the north northwest. This dip in this general area ranges from approximately 4 to 8 degrees from the horizontal. <br />' At the present ground surface, a Sandy gravel and gravel and cobble alluvial deposit was encountered. Numerous small Sand, <br />Silt and Clayey deposits are present on the ground surface, as a result of overbank flooding and normal river depositional <br />' processes. This coarse grained gravel and cobble deposit is the Present Terrace Deposit of the Colorado River. This gravel <br />and cobble deposit is believed to be between IS to 25 feet in thickness, based upon auger boring logs in this general area. <br />This is the gravel deposit which is to be extracted and processed. )n general, the upper 3 to 5 feet of the gravel and cobble <br />' is somewhat sandier and may contain some thin silt, sand and clayey deposits. The maximum cobble size is normally on the <br />range of 7 to 9 inches (square screened size) but the lower 4 to 6 feet of the deposit may contain occasional cobbles up to <br />12 to 16 inches in diameter. <br />The Dakota Formation is considered to be bedrock N this portion of the Grand Valley. The Dakota Formation is believed <br />to be less than 100 feet thick in this particular area, based upon exposures of the geologic rock section in the river bluff on <br />