The Fort Union, Indian Meadows, and Wind River Formations comprise a great wedge of fluviatile and lacustrine sediments, which accumulated in the Wind River Basin during Laramide deformation in Paleocene and early Eocene times.-A detailed knowledge of the stratigraphy, structure, and depositional history of these strata is fundamental to an understanding of the tectonic evolution of the basin and its surrounding uplifts. Such knowledge is also pertinent to many matters of economic interest, particularly exploration and development of oil and gas fields and uranium deposits.