--> ABSTRACT: Drowning of an Ooid Shoal: Mississippian Greenbrier Limestone Near West Virginia Dome, by Cindy Carney; #91023 (1989)
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Drowning of an Ooid Shoal: Mississippian Greenbrier Limestone Near West Previous HitVirginiaNext Hit Dome

Cindy Carney

The depositional setting for the Greenbrier Limestone of the central Appalachian basin included a continually subsiding basin, centered in southeastern West Previous HitVirginiaNext Hit and adjacent Previous HitVirginiaNext Hit, separated by a hinge zone from a broad shallow shelf located to the north and northwest. Oolitic limestones are thick and extensive in southern West Previous HitVirginiaNext Hit; however, most of these units thin drastically and change in lithology to the north. An area of uplift, the West Previous HitVirginiaNext Hit dome, developed along the hinge zone in north-central West Previous HitVirginiaNext Hit. During early Greenbrier deposition, this area was exposed as an island. Later, the dome was submerged but remained as a submarine high throughout Greenbrier sedimentation. The northernmost occurrences of Mississippian oolitic limestones in West Previous HitVirginiaTop surround this feature.

Soon after initial transgression, cross-bedded oolitic grainstones formed on ooid shoals around the flanks of the dome. Beds of micrite and dolomite characteristic of upper intertidal and supratidal environments developed over the dome itself. Fossiliferous wackestones were deposited in subtidal areas away from the uplift. Later, ooid deposition was interrupted temporarily by a pulse of terrigenous sedimentation. During continued transgression, ooid shoals became reestablished but differed from their predecessors. Water depth was slightly greater and conditions for development of thick oolitically coated grains were not as favorable.

Eventually, the epicontinental sea flooded the ooid shoals. As substrates became more stable, the shoals were colonized by a variety of benthic organisms. Conditions were far from ideal for ooid production in the flooded shoals and fossiliferous, poorly washed, oolitic packstones were deposited.

AAPG Search and Discovery Article #91023©1989 AAPG Eastern Section, Sept. 10-13, 1989, Bloomington, Indiana.