(Selma group), Chalk and marly chalk containing fewer impurities than underlying and overlying formations.
(Midway group), Dark-gray clay, north of Clay County contains slightly glauconitic, micaceous sand lenses.
(Selma group), Gray to greenish-gray fine glauconitic sand, clay, and sandy limestone; south of Oktibbeha County is very sandy micaceous chalk.
(Midway group), Upper part, greenish-gray coarsely glauconitic sandy clay and marl; lower part, crystalline sandy limestone and loose sand, represented south of Houston by a discontinuous bed of indurated calcareous sandstone.
(Selma group), Prairie Bluff chalk, compact brittle chalk, sandy chalk, and calcareous clay; at base contains many phosphatic molds of fossils; in Ponotoc and Union Counties merges northward into Owl Creek formation, tough blue glauconitic sandy clay.
(Midway group), Fine to coarse micaceous sand, kaolin, and bauxitic clay.