The Whitsett Formation of the upper Eocene Jackson Group contains, in ascending order, the Dilworth Sandstone, Conquista Clay, Deweesville Sandstone, Dubose, Tordilla Sandstone, and Fashing Clay Members. In Atascosa to McMullen Counties, the Calliham Sandstone Member, considered to be a stratigraphic equivalent of the Tordilla, is apparently the same age as the Fashing. The Deweesville is called the Stones Switch Sandstone Member by some geologists.

The Fashing contains flood-plain, lagoon-bay, and distributary-channel facies. The Kellner and Rosenbrock uranium mines are in the distributary-channel facies of the Fashing. These mines have previously been considered to be in the Tordilla Sandstone Member. The Calliham Member apparently represents tidal-delta sandstone at its type locality.

The Tordilla is a transgressive barrier-beach unit in the areas of the Pfiel-Wright and Weddington-Butler-Galen-Sickenius uranium-ore trends. Farther east, in the Manka and Stoeltje uranium mines, the Tordilla is represented by a back-barrier island facies.

Although the predominant facies of the Dubose is paludal and bay-lagoon mudstone, the ore in the Lauw and Bieker uranium mines is in a sand-filled distributary-channel facies.

A back-beach facies of the Deweesville contained the ore of the Searcy mine, and the F. Brysh mine is in the lower of two beach units in the Deweesville.

The sandstone members of the Whitsett Formation were deposited in transgressive barrier beaches, although locally they may be represented by progradational beaches or tidal inlets and deltas. Sandstone deposited in the distributary channels is equivalent in age to the clay members. The grains of the sandstone units in the Whitsett are composed mostly of feldspar and quartz. Some facies also contain abundant volcanic shards. Montmorillonite and clinoptilolite and part of the feldspar are authigenic constituents in the sandstone. The sandstone of the distributary channels is coarser grained than that in the beach sequences.

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