UPPER DEVONIAN (FRASNIAN) GONIATITE AND CONODONT MARKER BEDS IN THE HARRELL SHALE (APPALACHIAN BASIN) OF CENTRAL PENNSYLVANIA

A series of thin, styliolinid, limestones with distinctive goniatite and conodont associations have been located in the Harrell Shale along the Allegheny Front in Centre County, Pennsylvania. The horizons match a succession of fossil beds in the Genesee Formation of New York.

At Milesburg, a pair of concretion horizons with Koenenites styliophilus and Acanthoclymenia with Ancyrodella rotundiloba and A. crosbiensis (conodont Zone MN 2) outcrops in the Harrell Shale below a 40 cm black shale in the entrance-ramp section of I-80 West. The association matches the fauna of the Crosby Sandstone in the Penn Yan Shale in New York. The Crosby-equivalent horizon also crops out along Route 150 at nearby Curtin. Higher in the Milesburg section, about 15 meters above the black shale, a styliolinid bed yields, Koenenites aff. styliophilus, Manticoceras contractum and Ancyrodella recta (Zone MN 3), the characteristic fauna of the mid-Genesee Genundewa Limestone. A similar Genundewa fauna occurs in a bed in the Harrell Shale on Route 220 at Unionville. Still higher in the Milesburg section, some 6 meters above the Genundewa level, a styliolinid bed yields Koenenites aff. lamellosus and Ancyrodella alata (Zone MN 4) a fauna that occurs in a concretionary bed near the Bluff Point Siltstone in the middle of the post-Genundewa West River Shale in New York.

These widespread fossil beds record discontinuities in the accumulation of clastic sediments in the basin, formed during intervals of sediment starvation associated with high stands of sea level. Work continues to extend the correlations into the more proximal facies of the Catskill Delta succession. The Bluff Point level may be represented in an interval in the upper Harrell at Lock Haven, Clinton County, which yields molds of Koenenites and possibly Labotornoceras aff. hassoni House, a species in the Bluff Point level in New York and close to the types of L. hassoni from the Harrell Shale of West Virginia. The occurrences in Pennsylvania and West Virginia of pelagic faunas known from New York is evidence that the migration route into the Appalachian Basin during the early Frasnian was from the south via a Euro-African seaway link.