ARKANSAS NOVACULITE FORMATION
Age: Devonian and Early Mississippian Periods
Distribution: West-central Arkansas, Ouachita Mountains; southeastern Oklahoma; equivalent novaculite-bearing formation in Texas is the Caballos Novaculite
Geology: Three Divisions of the Arkansas Novaculite Formation are recognized (except in the northern exposures). The Lower Division is a white, massive-bedded novaculite with some interbedded gray shales near its base. The Middle Division consists of greenish to dark gray shales interbedded with many thin beds of dark novaculite. The Upper Division is a white, thick-bedded, often calcareous novaculite. Conodonts and other microfossils are sometimes common in the Arkansas Novaculite. The formation rests conformably on the Missouri Mountain Formation at most places, but the presence of conglomerates in a few places suggests a possible minor incipient submarine disconformity. The formation may attain a thickness of up to 900 feet in its southern outcrops, but thins rapidly to about 60 feet to the north.
Original reference: A. H. Purdue, 1909, Slates of Arkansas: Arkansas Geological Survey, p. 30, 39-40; (L. S. Griswold, 1892, Arkansas Geological Survey Annual Report 1890, V. 3, p. 57-61, 69, 85, 87-113).
Type locality: Named for quarries in Arkansas (especially near Hot Springs in Garland County) that produced this rock under the trade name of "Arkansas Novaculite"