Salt Flat graben is an intermontane basin in Hudspeth and Culbertson Counties, western Texas. The basin is filled with Quaternary sediments that include dolomite distributed among evaporite minerals. Carbon-14 dating indicates an age of 20,300+ or -825 years for one dolomite. Dolomite occurs at stratigraphically persistent levels associated with discontinuous lenses of native sulfur, gypsum, halite, and calcite. Dolomite was formed during periods of intense evaporation.