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ABSTRACT The principal occurrence of the Paradox formation is in a northwest-southeast trending basin west of the Uncompahgre uplift, chiefly in southwest Colorado and adjacent portions of southeast Utah. It extends, roughly, from Barker Dome on the Colorado-New Mexico line, northwestward to the vicinity of Green River, Utah. It is approximately 200 miles long and 115 miles wide. The town of Monticello, Utah, is near the geographical center. It is a structural basin lying between the Uncompahgre-San Juan Mountains on the east and the San Rafael-Circle Cliffs upwarps on the west. It is separated from the San Juan basin on the south by a relatively low saddle, and perhaps from the Uinta basin to the north by a similar saddle. The Paradox is a depositional wedge, within the Hermosa formation. It is lower Pennsylvanian in age. Similar sediments of black shale, gypsum, and anhydrite of Pennsylvanian age occur in the Eagle-Glenwood Springs area, east of the Uncompahgre and on the east flank of the White River uplift. While these sediments probably are equivalent to the Paradox formation, there is no evidence to indicate that the basins were ever connected, and the term Paradox formation has not been applied, officially, to the sediments in the Eagle basin. The chief exposures of the Paradox occur in Gypsum Valley, Paradox Valley, Sinbad Valley, in Colorado, and in Moab-Spanish Valley, Onion Creek, and Cache Creek-Salt Valley in Utah; all of which are commonly referred to as breached salt anticlines. In these exposures the Paradox consists of irregular beds of gypsum, limestone, dark shales and some find sands. In many places these beds are highly contorted and brecciated, indicating flowage from a deeper source, and contain blocks of foreign material dragged up from below. The maximum thickness of the Paradox is unknown, but in one occurrence it exceeds 10,800 feet, although this undoubtedly represents flowage rather than depositional thickness. Several wells which have drilled a normal section have had in excess of 2,000 feet. The section is so irregular that no correlation horizons which can be used for more than local work have been established. In the salt anticlines the section is so garbled and twisted that little bedding remains, and thickness cannot be established. No exposure out in the basin exhibits the base, but in Salt Valley blocks of conglomerate, believed to have been dragged up with the salt, may represent the underlying formation.
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