Geology of the Puddle Springs quadrangle, Fremont County, Wyoming

Abstract

The Puddle Springs quadrangle is near the south-central edge of the Wind River Ba,sin in central Wyoming. It includes most of the western part of the Gas Hills uranium district, and the original uranium ore reserves totaled at least 1 million tons.Although Cambrian, Mississippian, and older Pennsylvanian strata may be present in the subsurface, all drill holes have bottomed in or above the Tensleep Sandstone of Pennsylvanian age. At least 16 oil and gas test holes have been drilled, and they penetrate formations of Permian, Triassic, Jurassic, and Cretaceous age. Rocks exposed at the surface include the Mowry Shale of Early Cretaceous age, Frontier Formation and Cody Shale of Late Cretaceous age, Wind River Formation of early Eocene age, Wagon Bed Formation of middle and late Eocene age, and pediment gravel and alluvium of Quaternary age.Only the ore-bearing Wind River Formation, which underlies about half the quadrangle, was studied in detail. Composite thickness of this formation ip about 826 feet, but the greatest thickness in any one locality now is about 600 feet. The formation includes a lower fine-grained member, the coarse-grained Puddle Springs Arkose Member, and an upper transition zone.The lower fine-grained member ranges in thickness from 0 to about 130 feet and i^ composed of siltstone, fine-grained sandstone, claystone, a few beds of partly coaly carbonaceous shale, and a thin irregular basal bed of conglomerate.The Puddle Springs Arkose Member is more than 500 feet thick and consists of massive coarse conglomeratic arkosic sandstone and beds of granite granule-toboulder conglomerate, fine-grained sandstone, siltstone, claystone, and carbonaceous shale. This member has all the known uranium deposits in the quadrangle. The arkose is generally oxidized and yellow to gray at the surface but is unoxidized and greenish to bluish gray near and below the water table. Two granite cobble-and-boulder conglomerate beds were mapped in the Puddle Springs quadrangle; they are about 10-30 feet thick and 100 feet apart stratigraphically. The lower of the two, the Dry Coyote Conglomerate Bed, contains many uranium deposits; most uranium deposits in the quadrangle lie from 150 feet below to 50 feet above this bed. The overlying Mnskrat Conglomerate Bed has no known uranium deposits. ClC2 CONTRIBUTIONS TO ECONOMIC GEOLOGY GEOLOGY OF PUDDLE SPRINGS QUADRANGLE, WYOMING C5 Puddle Springs Ranch &' I \?£UREKA MIN SAGEBRUSH Uranium Co camp Uranium Co DICK 7. 8. AND 9 MINES HUNTER \// LEASE PHIL HOPE MINES MINE ANDRIA MINE AEC core hole GH-1 MILE J ' Composite thickness: maximum thickness of the formation in any one locality is about 600 ft and, of the Puddle Springs Arkose Member, about 500 ft.