A zone of lignite beds of Paleocene age in the Denver Formation (Upper Cretaceous and Paleocene) lies about 800-1,500 feet above the well-known and extensively mined coal beds of the Laramie Formation (Upper Cretaceous). The zone is a few hundred to as much as 500 feet thick. Where lignite beds lie within 1,000 feet of the surface, this zone underlies an area about 30 miles wide by about 75 miles long, stretching from just northeast of Denver to several miles south of Calhan. Fifteen mines were operated at various periods between 1874 and 1940 and probably produced a total of less than 100,000 tons of lignite, mostly for local use. the base. Available analyses indicate that the following general figures, on an as-received basis, may be applied to relatively clean lignite from this zone: 6,000-7,000 Btu, 20-35 percent moisture, 8-18 percent ash, and 0.3-0.5 percent sulfur. Rank of the lignite is lignite A as calculated by the formulas of the American Society for Testing and Materials (ASTM), although some parts, especially of deeper beds, may be as high as subbituminous £ coal in rank.Best utilization of the lignite probably would be by gasification, liquefaction, or similar methods, because of the numerous non-coal partings and low quality.The thickest known lignite bed is estimated to contain at least 1.25 billion short tons of lignite. Two methods of roughly estimating the order of magnitude of lignite resources, in beds at least 4 feet thick and within 1,000 feet of the surface in this zone, indicate resources are on the order of 20 billion tons.
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.
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