11 Paleontology (Posters)

PALEOBIOLOGY OF A LATE DEVONIAN OFFSHORE COMMUNITY AND THE POSITION OF THE FRASNIAN-FAMENNIAN BOUNDARY NEAR ELKINS, WEST VIRGINIA

Paper number: 11-4
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Roadcut operations northwest of Elkins, West Virginia, have exposed very fossiliferous dark gray siltstones. The fine nature of the sediment has allowed detailed fossil preservation which in turn has facilitated species identification. Paleoenvironmental and faunal analyses suggest these sediments were deposited approximately 9.5 kilometers offshore during the Late Devonian. On the genus level, pelecypods are almost as diverse as brachiopods, which is atypical for faunas of this age in West Virginia. The fauna is also unusual in containing large orthocerid nautiloids.

Identification of several index fossils indicates the outcrop is of Frasnian age and faunally equivalent to the lower members of the Foreknobs Formation (Mallow through Blizzard Members). Several of the Frasnian index fossils disappear within a few meters of each other suggesting a well defined placement for the Frasnian-Famennian boundary. However, no definite Famennian age index fossils have been recovered above this level. One hypothesis to explain this pattern is that since the Elkins outcrop was deposited farther offshore than the deltaic sediments of the Foreknobs Formation, the typical Famennian index species may not have migrated into these deeper waters after the Frasnian-Famennian extinction event, obscuring the exact boundary.