Abstract

Reconnaissance in the White Canyon district, San Juan County, Utah, indicates that rocks of the Shinarump member of the Chinle formation of Triassic age were deposited in that district in 2 different channel systems; sediments deposited in channels of one system were derived from a source to the E. and the sediments of the other from a source to the S. The channel system containing sediments derived from the E, the Elk Ridge-White Canyon channel system, was apparently formed by a large braided stream that flowed westward from a source in granitic and metamorphic terrane of the ancestral Uncompahgre highland. All known U deposits of any consequence in the White Canyon district are confined to the Shinarump member deposited in the Elk Ridge-White Canyon channel system. The nature of the channels and the lithologic characteristics of the rocks filling this system of channels combine to form a much more favorable environment for the localization of U deposits than do the channels formed and the rocks deposited by northward-flowing streams. Recognition of channel systems in the White Canyon district suggests that channel systems may be recognized elsewhere in the Shinarump member, and that the Shinarump member on the Colorado Plateau may be composed of rocks deposited in many coalescing channel systems. In addition, study in the White Canyon district indicates that rocks deposited in some of these channel systems are more favorable hosts for U deposits than the rocks deposited in others. Recognition and delineation of these ancient channel systems may be of help in making regional appraisals of ore potential and in the search for new mining districts.

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