ANNONA CHALK/FORMATION

Age: Late Cretaceous Period, Gulfian Series
Distribution: Gulf Coastal Plain in southwest Arkansas in parts of Hempstead, Howard, and Little River Counties; Texas, Louisiana, Oklahoma
Geology: The Annona Chalk is a hard, thick-bedded to massive, slightly fossiliferous chalk. It weathers white, but is blue-gray when freshly exposed. The unit is commercially mined for cement. 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.
Original reference: R. T. Hill, 1894, Geological Society of America Bulletin, v. 5, p. 308.
Type locality: Named for outcrops about 2 miles northwest of Annona, Red River County, Texas


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