A biostratigraphic study of Upper Devonian rocks at Kates Mountain in Greenbrier County, West Virginia, suggests that the Frasnian-Famennian stage boundary here is stratigraphically higher than its customary level elsewhere in the central Appalachian basin. The study revealed a range extension of two Frasnian taxa, the atrypid brachiopods Spinatrypa hystrix (Hall, 1843) and Spinatrypa spinosa (Hall, 1843) into nominally Famennian age strata.

Fossils were collected from more than 100 stratigraphic horizons in the Foreknobs Formation exposed on Kates Mountain. The Frasnian-Famennian stage boundary has traditionally been placed where atrypid brachiopods disappear and the athyrid brachiopod Athryis angelica Hall, 1861, first appears. This boundary has conventionally been placed within the Pound Member of the Foreknobs Formation or at its contact with the overlying Red Lick Member. This faunal change at Kates Mountain, however, is very precisely located within the lower Red Lick Member, where S. hystrix and S. spinosa range to within one meter of the first occurrence of A. angelica. This might be the youngest known occurrence of S. spinosa, which is usually restricted to the much lower Mallow Member. Spinatrypa spinosa has previously been reported from the Red Lick Member at Huttonsville, West Virginia, but the stratigraphic boundaries there have been questioned. The stratigraphy on Kates Mountain, however, is very well defined and definitely shows atrypids extending into the Red Lick. These findings support the view that the Pound Member, usually cited as a marker for the Frasnian-Famennian boundary, is diachronous within the central Appalachian basin.