253-10 Late Missourian (Upper Pennsylvanian) Conodonts From the Broad Top Coal Field, South-central Pennsylvania, USA, and Their Stratigraphic and Paleogeographic Implications.

Session: Conodonts from North America and Beyond - Honoring the Career of Dr. James E. Barrick

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Abstract:

The Broad Top coal field is a structurally isolated area of Pennsylvanian outcrop in south-central Pennsylvania. A conodont biostratigraphic study from a subsurface core in Broad Top was performed to refine correlations of these strata to those from the main bituminous coal fields of western Pennsylvania and to the anthracite coal fields of eastern Pennsylvania. Ten prospective marine units were identified and one of them yielded a well-preserved Late Missourian conodont fauna containing Streptognathodus, ‘Streptognathodus’ group 2, Hindeodus, and Adetognathus. Other nearshore marine fossils were also recovered including ostracodes, pelecypods, gastropods, bryozoans, foraminifera, rugose corals, fish, crinoids, and echinoids. The conodont biostratigraphy and lithostratigraphy place the Broad Top marine unit closest in chronostratigraphic position to the Noble and the Woods Run marine units of western Pennsylvania and Ohio. The Broad Top condonts are more like those described from the Noble because both faunas are dominated by ‘S.2’ firmus Kozitskaya; however key differences prohibit confident correlation between them including morphological differences of ‘S.2’ firmus between the two units and the lack of Streptognathodus in the Noble. The Noble marine zone is also poorly developed in western Pennsylvania, making it difficult to explain the presence of a marine unit in Broad Top without a clearly developed western (the distal depositional direction) correlative. The Woods Run marine zone is considered to extend further east into Pennsylvania, but its conodont fauna is quite different from what is observed at Broad Top, comprising entirely of Streptognathodus species with no ‘Streptognathodus’ group 2. A new possible correlation is proposed where the Broad Top marine unit represents a distinct marine sequence in between the Woods Run and Noble that is either eroded, unrecognized, or was never deposited in western Pennsylvania and Ohio. Written descriptions of conodonts from the Mill Creek Limestone in northeast Pennsylvania are very similar to what is described in Broad Top and these two units may be correlative. The possibility of a Pennsylvanian marine unit in east-central Pennsylvania without a western correlative invokes significant questions about the paleogeography and marine pathways into the northern Appalachian Basin during the Late Missourian.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7756

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