Chester (Mississippian) Ostracodes from Bangor Formation of Black Warrior Basin, Northern Alabama
Hugh Devery, Chris Dewey
A previously unreported ostracode fauna is described from the Bangor Limestone in Franklin, Lawrence, and Colbert Counties, Alabama. The Bangor formation is a Chesterian (Mississippian) platformal carbonate sequence. The predominant carbonates are bioclastic and oolitic grainstones to wackestones with less abundant micritic claystones. Intercalated fine clastics are common in the upper and lower parts of the sequence. This study focuses on the bioclastic limestones with interbedded shales of the lower Bangor.
The megafaunal associations include crinoid and blastoid pelmatozoans, orthotetid, and spiriferid brachiopids, and both fenestrate and nonfenestrate bryozoans. Solitary rugose corals and trilobites may be locally abundant. Gastropods and bivalves form a consistent but accessory part of the fauna, which indicates a shallow, nearshore shelf environment.
A diverse ostracode fauna of variable abundance has been collected from the shaly units and friable limestones. The ostracode fauna indicates shallow, open-marine conditions and is dominated by bairdiaceans, including Bairdia spp. Rectobairdia and Bairdiacypris. Several species of Cavellina, Healdia, and Seminolites are also abundant. Palaeocopids present include Coryellina, Kirkbya, and Polytylites. Kloedenellaceans include Beyrichiopsis, Glyptopleura, Glypotpleurina, and ?Hypotetragona. Paraparchitaceans are notably more scarce, but specimens of Shishaella have been found.
Some samples have a high valve to carapace ratio, suggesting postmortem transport. Although diversity is high, numerical abundances can be low.
Initial studies suggest the ostracodes have a Mid-Continent affinity, which may indicate that the Appalachians were acting as a barrier to migration of European forms.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.