The southern part of the eastern Greater Green River Basin is the Washakie Basin, a sedimentary basin south of the Wamsutter arch. This large basin lies west of the Sierra Madre, east of the Rock Springs uplift, and north of a structural arch called Cherokee Ridge that separates the Washakie Basin from the Sand Wash Basin in Colorado. The Washakie Basin is deepest and most structurally complex along its southwestern and southern edges, where dips are steepest and several zones of faulting are present. Rocks exposed at the surface in most of the basin are relatively flat lying, with the topography controlled mostly by differences in resistance to erosion.
Like the Great Divide Basin, the Washakie Basin contains a thick sequence of marine Upper Cretaceous and continental early Tertiary rocks, along with lacustrine rocks of the Eocene Green River Formation. The interior of the basin also contains an extensive area of mostly stabilized, but some active, sand dunes. Most of the interior of Washakie Basin is undeveloped; part of the area has unusual and unique landforms and erosional features called Adobe Town. This area of more than 280 square miles in the central part of the basin contains lands that have been designated “very rare or uncommon [with] particular historical, archeological, wildlife, surface geological, botanical, or scenic value.”