The soil formed in loamy sediments. These include the Brennan , Copita , Cuevitas , Jimenez , Quemado , and Randado series. Brennan and Copita soils have sola more than 20 inches thick, and do not have a petrocalcic horizon. Brennan, Copita, Cuevitas, and Randado soils occur at slightly lower elevations. Jimenez and Quemado soils occur on surfaces similar to Zapata soils.
Permeability is moderate over a very slowly permeable petrocalcic horizon.
Runoff is very high. The principal grasses include a sparse cover of tanglehead, plains bristlegrass, twoflower trichloris, hooded windmillgrass and perennial threeawn. Common brushy plants are blackbrush, cenizo, guajillo, kidneywood, and ratany. The series is extensive.