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2.04.6 <br />deposition in the Eastern Piceance Basin. The coal deposits of the area were <br />deposited as the complex relationships of deltaic, fluvial, and barrier island <br />facies were intermittently modified by transgressive- regressive cycles of the <br />retreating Cretaceous shoreline. <br />The coal bearing member of the Mesaverde formation locally contains up to <br />nine mineable coal seams in the North Fork Valley, named in ascending <br />alphabetical order, within the stratigraphic interval 500 to 600 ft. above the <br />Rollins Sandstone Member (Dunrud, 1976). Mines recently operating in the <br />various coal seams are as follows: Somerset - C & B -2; Sanborn Creek - C & <br />B -2; Bowie No. 1 - D -2; Blue Ribbon and Hawks Nest - E -1; Bear - C & B -2; <br />Mountain Coal Company - F & B -2. Due to the depositional environment of <br />the coal bearing member, individual coal seams are not laterally continuous <br />nor do they maintain uniform thicknesses from differing locations throughout <br />the area. <br />The barren member of the Mesaverde formation is lithologically similar to the <br />coal bearing member with the exception of virtually no mineable coal seams. <br />In the North Fork area, the barren member is stratigraphically between the F <br />coal seam and the Ohio Creek conglomerate, and was estimated by Lee <br />(1912) to be 1500 ft. thick. The scarcity of coal deposits within the barren <br />member probably represents progradation of terrigenous, nonmarine <br />sediments deposited in response to the retreating shoreline. Hail (1972) <br />reports maximum thickness of the entire Mesaverde Formation to be about <br />2300 ft. <br />The Paleocene Ohio Creek Formation unconformably over lies the <br />Mesaverde formation. The Ohio Creek Formation consists of light -gray, <br />locally conglomeratic sandstone which ranges in thickness from locally 0 ft. to <br />a maximum of 200 ft. Where the conglomeratic facies is lacking or obscured <br />by surficial deposits, the Ohio Creek Formation is mapped within the <br />Mesaverde Formation (Hail, 1972). <br />The Eocene Wasatch Formation consists of variegated mudstone and <br /> - - - - siltstone with- interbedded - medium gray lenticular sandstone, which is-locally -- - -- -- <br />conglomeratic (Junge, 1978). Maximum thickness is reported to be <br />approximately 1600 ft. (Hail, 1972), although exposures are largely obscured <br />PR -12 2.04-15- 02/10 <br />' APPkcv 6 D <br />(/1(6 [I o <br />