PALYNOMORPH BIOSTRATIGRAPHY OF LATE DEVONIAN STRATA IN NORTHEAST WEST VIRGINIA

Samples collected from a road cut along U.S. Route 48, near the town of Bismarck in Grant County, WV, were palynologically analyzed to determine the relative age of the sampled interval. The section includes the upper part of the Hampshire Formation, which consists of red bed shales and siltstones with infrequent coal lenses, and the overlying Rockwell Member of the Price Formation. The Rockwell Member at this location consists of sandstone, siltstone, shale and two thin, but conspicuous, diamictite beds. Recovered palynomorphs are dark in color, and coal fragments in the Hampshire Formation have vitrinite reflectance levels of 1.8 to1.9 %, indicating an elevated level of thermal maturity.

Palynologically, all the samples contain Retispora lepidophyta, which is a Late Devonian palynomorph index taxon. Common miospore taxa include species of Apiculiretusispora and Retusotriletes. Additional taxa include Discernisporites sullivanii, Kraeuselisporites mitratus, Tumulilisporites malevkensis, Vallatisporites pusillites, V. microspinosus, V. verrucosus and Spelaeotriletes crustatus. Biostratigraphically, samples from the Hampshire Formation best conform to the Retispora lepidophyta – Indotriradites explanatus (LE) miospore biozone, whereas samples from the overlying Rockwell Member are assignable to the Retispora lepidophyta – Verrucosisporites nitidus (LN) miospore biozone. Both biozones are indicative of a Late Famennian (Late Devonian) age assignment.

The outcrop interval correlates with the Cleveland Member of the Ohio Shale and overlying Bedford Shale of the Borden Formation in eastern Kentucky. The diamictites in the Bismarck outcrop represent one of the westernmost occurrences of this unique lithology in the Appalachian region. Contemporaneous diamictites have been documented in South America, suggesting that the Late Devonian was a time of widespread climatic cooling with expanded glaciation, especially in the southern hemisphere.