The Laney Member of the Green River formation is a sequence of Eocene age rocks which are found in the southwest quarry of Wyoming and parts of northwest Colorado. In general, the Laney crops out along the margins of the Green River, Great Divide, Washakie and Sand Wash Basins of Wyoming and Colorado. The Laney is primarily a carbonate shale section which was deposited in or around ancient Lake Gosiute. Time transgressive sequences within the Laney Member of the Green River Formation indicate that ancient Lake Gosiute migrated into the study area late in its history and eventually terminated there. The termination of Lake Gosiute was preceded by progradation, freshening, and the development of an outlet. Through these processes, the Laney sediments in this area acquired unique lithologic, mineralogic and paleontologic characteristics relative to Laney rocks elsewhere. Two specific mineralogic characteristics which are unique to the area are the presence of cristobalite in some units, and the absence of evaporite minerals. The most striking lithologic difference between the Laney rocks of Wyoming and the Laney rocks of Colorado is the overall abundance of non-kerogeneous shales in Colorado. The lithologic, mineralogic and paleontologic characteristics and the cyclic nature of these characteristics are typical of playa-lahe deposition. In summary, the Laney rocks of Wyoming were deposited in a large, penesaline playa lake; whereas, the Laney rocks of northwest Colorado were deposited in a much smaller and relatively fresher water lake. Since the Laney rocks of Wyoming and Colorado were deposited in the same lake, many Laney stratigraphic units cross time lines. The Laney rocks of northwest Colorado, therefore, represent the final stages of deposition in Eocene Lake Gosiute.