Laserfiche WebLink
and is divided into four main members - <br />Bearing (Bowie) member, the Upper Coal <br />(Undifferentiated) member. <br />the Rollins Sandstone, the Lower Coal <br />Bearing (Paonta) member, and the Barren <br />The Rollins Sandstone member is a 120- to 300-font-thick, massive, <br />cross-bedded, medium- to fine-grained, buff to white sandstone. This <br />sandstone is regionally extensive and resistant in outcrop and forms prominent <br />cliffs. This member is used regionally as a marker horizon to define the top <br />of the Mancos Shale and the bottom of the coal-bearing horizons. <br />The Lower Coal Bearing. (Bowie) member consists of 260 to 350 feet of <br />interbedded gray shales, thin to thick' lenticular beds of buff-colored, fine- <br />to medium-grained sandstones, and coals. The top of the member is usually <br />capped by a massive buff-colored sandstone up to 90 feet in thickness. This <br />sandstone, however, appears not to be a single persistent bed, but is actually <br />several thick lenticular sandstones occurring at progressively lower <br />stratigraphic horizons from east to west. <br />Three coal beds exist in the Lower Coal Bearing member - the A (Old King) <br />horizon, the B (Somerset) horizon, and the C (Bear) horizon. The A horizon is <br />immediately above the Rollins sandstone and is not currently mined. The <br />B horizon contains two coal seams and occurs about 20 to 120 feet above the <br />Rollins sandstone. The C horizon contains one coal seam that occurs 50 to <br />100 feet above the B horizon. <br />The Upper Coal Bearing (Paonia> member consists of 200 to 500 feet of gray <br />shales, interbedded, buff-colored, lenticular sandstones, and coals. The top <br />of this member usually grades into a massive, cliff-forming sandstone. <br />However, like the similar sandstone at the top of the Lower Coal member, this <br />sandstone is not a single persistent bed. <br />Three coal horizons have been identified in the Upper Coal member - the <br />D (Oliver) horizon, the E (Hawk's Nest) horizon, and the F horizon. The <br />D horizon occurs directly above the "massive" sandstone of the lower Coal <br />Bearing member and contains three seams. This horizon is currently being <br />mined in the Orchard Valley Mine. The E horizon occurs about 130 feet above <br />the D horizon and contains two coal seams. The F horizon contains two coal <br />seams. Coal seams of the F horizon do not exist to the north of tfie North <br />Fork in thicknesses sufficient for mining. <br />The Barren (Undifferentiated) member of the-Mesaverde Formation consists of up <br />to 1,500 feet of terrestrial sedimentary rocks. This unit consists of <br />fine-grained, buff-colored, lenticular sandstones, gray shales and thin, <br />lenticular coal beds. The sandstones predominate and are highly lenticular, <br />discontinuous and of limited lateral extent in outcrop. <br />The Mesaverde Formation is unconformably overlain by the Tertiary Age Rudy or <br />Wasatch Formation. This formation consists of red to buff-colored shales, red <br />sandstones, and red to gray conglomerates. The sediments of this formation <br />are weathered volcanic rocks. 'The Ohio Creek conglomerate is the basal unit <br />within the formation and is 100 to 200 feet thick. <br />_12_ <br />