The R layer is indurated limestone. It is layered and fractured and has carbonate coatings in the upper part. Brownish, pinkish, whitish, olive, and grayish clays, clay loam, caliche, chalks, and marls are between some of the limestone layers. Similar soils are the Eckert , Eckrant , Latom , Lozier , Palopinto , Purves , Talpa , Tarrant , and Volco series. Aledo, Eckert, and Palopinto soils do not have a calcic horizon.
Altuda soils are dry in the soil moisture control section for slightly longer periods of time.
Eckrant, Purves, and Tarrant soils have smectitic mineralogy. Ector, Lozier, and Volco soils are dry in the moisture control section for longer periods of time. Latom soils are less clayey and are developed from sandstone. Oplin soils developed in limestone of Cretaceous age materials. Talpa soils have less than 35 percent coarse fragments in the control section.