Mississippian Bioherms in Northeast Oklahoma

Abstract

In northeast Oklahoma, the Mississippian Boone formation contains numerous striking bioherms composed of crinoidal debris. Most of the exposed bioherms occur in the St. Joe, or lowest member of the Boone formation. The Reeds Spring, or middle member, contains no bioherms, and the Keokuk, or upper member, contains a few known bioherms. The bioherms occur in widespread, thin-bedded crinoidal limestones and are related in origin to the thin-bedded limestones. Each bioherm consists of a lens-shaped core of massive limestone which is surrounded by and interfingers with thin-bedded limestones. The massive cores are 10-40 feet thick and 50-1,000 feet wide. The thin-bedded limestones dip steeply away from the massive cores. The bioherms are interpreted as having been formed by the accentuated growth and accumulation of crinoids. The bioherms formed mounds which were elevated as much as 50 feet above the floor of a shallow sea. The massive bioherm cores were probably created by the continuous deposition of crinoidal debris; whereas the bedded limestones represent deposition which was interrupted from time to time. The thin-bedded limestones on the flanks of bioherms were deposited on slopes as steep as 45°. A debris-binding agent, such as inorganically precipitated calcium carbonate or calcareous algae, is postulated to have bound the deposits of crinoidal debris together, permitting them to persist on such steep slopes. The bioherms are considered to have been organic reefs because they formed wave- esistant organic structures which formed elevated prominences in a shallow sea.