The fluvial tower Eocene Wind River Formation crops out throughout most of the Wind River Basin. The geology of the Wind River Formation is important from an economic point of view, as it is the host rock for important quantities of hydrocarbons and uranium. Soister (1968), Van Houten (1964), and others have written detailed accounts of the stratigraphy of the Wind River Formation in specific parts of the basin, and Keefer (1965a) has presented a more regional view. These works will provide a background for the sedimentologic and stratigraphic data and interpretations of this paper.