Geological Society of America Bulletin, v. 5, p. 308

The Annona Chalk is a hard, thick-bedded to massive, slightly fossiliferous chalk. It weathers white, but is blue-gray when freshly exposed. Fossils in the Annona Chalk include coelenterates, echinoderms, annelids, bivalves, gastropods, cephalopods, and some vertebrate traces. The Annona rests conformably upon the Ozan Formation. The formation varies from 0 to 100 feet in thickness.

Journal of Paleontology, Vol. 67, No. 1

The stratigraphy, facies, and paleoenvironments of the unit were described by Dane (1929) and Bottjer (1978, 1981, 1985, 1986); Bottjer reviewed previous literature, and showed the unit to be as much as 90 m (300 ft) thick in Texas (also see recent review by Thompson et al., 1991). However, it thins markedly in southwestern Arkansas from 27 m (89 ft) in Little River County to 10.4 m (34 ft) in Howard County to only 36 cm (1.2 ft) between Columbus and Yancy in Hempstead County. The Annona wedges out to the northeast and the overlying Marlbrook Marl comes to lie on the underlying Ozan Formation.