This is an evaporitic mudstone unit of Late Jurassic age present only in the subsurface; two members, an upper and a lower, are recognized. Nodular anhydritic mudstone and nodular anhydrite are the most common rock types. The nodules are lathy anhydrite occurring in a groundmass of blocky to anhedral grains. The matrix is mudstone, with illite and chlorite. Laminated anhydrite is the next common type. The Buckner was deposited in basins paralleling the Gulf Coast embayment margin. Salt-cored anticlines along the seaward margins restricted the circulation. In general, the sea was regressing during the time of the Buckner deposition. Nodular anhydrite is associated with brackish-water fossils and was probably deposited as gypsum. Microgranular anhydrite is associated with rock salt and is here considered to be primary.