Quaternary alluvium in valley-flats of the Davis Mountains and adjoining low‐lands in Trans-Pecos Texas contains remains of extinct horse and mammoth species as well as artifacts and other cultural material. On the basis of disconformities within the valley-fill complex, the Quaternary has been divided into three formations: Neville, Calamity, and Kokernot, in order from oldest to youngest.
Although the formations are alike in that they consist of silty clay, silt, sand, and gravel derived from local bedrock, differences in color and caliche content aid in their differentiation. The Neville is typically reddish brown to buff, whereas younger formations are generally gray. Caliche concretions and cement, abundant in the Neville, are uncommon in the Calamity and generally absent in the Kokernot.
Only the Neville contains mammoth remains. To date, no artifacts have been found in the Neville, although the overlying Calamity formation contains artifacts, buried hearths, and human skeletons. Archeologists believe . . .