Abstract

The oldest strata of the Late Triassic Dockum Formation in West Texas are assigned to the Camp Springs Member, which is up to 15 m thick and is dominantly micaceous litharenite, arkose, and extrabasinal siliceous conglomerate. This conglomeratic unit is a distinctive marker bed throughout most of West Texas that allows easy recognition of the Permian-Triassic boundary. It rests with profound unconformity on Late Permian strata and is disconformably overlain by red beds of the Iatan or Tecovas Members of the Dockum Formation. Fossil vertebrates (Metoposaurus, Paleorhinus) from the Camp Springs Member indicate it is of late Carnian (Tuvalian) age. Rising base level resulted in Camp Springs deposition by rivers on an incised topography developed in Late Permian strata. The base of the Dockum Formation is rarely a mudstone or siltstone. No Early or Middle Triassic strata are known in West Texas where the Permian-Triassic contact is a profound unconformity that represents about 25 million years.