2003-06-16_PERMIT FILE - C1981041 (4)

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2.04.6 Geology Description (3)(a) Underground Mining The area to be affected over the life of the operation is part of Bookcliffs coal field which is an outcropping of the Mesa Verde Group. The Bookcliffs coal field is on the southern rim of the Unita Basin and structurally lies within the basin. The southern structural rim of the basin falls along the crest line of the Uncompahgre uplift, some 30 miles to the south. The coal seams of the project area occur in the Mount Gartield Formation of khe Mesa Verde Group. The localized general structure in the vicinity of the Roadside South permit area is characterized as a monoclinical structure dipping at 2° to 5° to the North Northeast. The general surface geology is mapped in Exhibits 13 and 39. Details on these exhibits are taken from: Cashion, W.B., 1973, Geologic and Structure Map of the Grand Junction Quadrangle, Colorado and Utah: U.S. Geol. Survey Misc. Geol. Inv. Map I-736. 1:250,000. The general stratigraphy and structure are depicted in the cross section and geologic column of Exhibits • 14, 40, 43 and 44. Four coal zones containing definable seams outcrop along the face of the Bookcliffs in Colorado. The highest has been named the "Carbonera Coal Zone". Two or three seams are usually present in this zone. About 60 feet below is the Cameo Coal Zone, named for the old mining town of Cameo. One or two seams are commonly present in this zone. Where there are two seams, the interval between them is 30 feet or less. The Cameo seam immediately overlies the Rollins Sandstone. The interval between the base of Cameo Coal Zone and the base of the Palisade Coal Zone, the next lower, ranges from 200 to 450 feet across the field, being greater in the East. The Sego Sandstone underlies the Palisade Zone and is a regional formation correlation marker. The earliest mining operations in the field were in one of the lenses of the palisade '. 6-1 (Rev. 12119/96)