VERTICAL AND LATERAL STRATIGRAPHIC VARIATIONS WITHIN THE UPPER DEVONIAN CATSKILL SHORELINE IN NORTH-CENTRAL PENNSYLVANIA

Although significant research has focused on the depositional setting of the Upper Devonian Catskill Formation, there remains a lack of detailed understanding regarding facies distributions, sediment dispersal trends, and shoreline dynamics in response to internal and external forcing mechanisms. This largely results from minimal complete exposures of the Catskill Formation, which hinders regional correlation of key stratigraphic surfaces and depositional facies trends. However, two cores acquired by the PA Geological Survey that are spaced 16 km apart along a NE-SW oriented trend (Norwich Core (MCK083_0406): McKean County; Rich Valley Core (CAM023_0581): Cameron County) and capture the entire Catskill Formation (~95-120 m thick), along with 463 wireline log suites, have facilitated detailed facies descriptions and interpretations, and correlation of key stratigraphic surfaces across north-central Pennsylvania. Key findings from a detailed facies analysis reveals vertical and lateral variations between both cores, including total thickness differences of the Catskill Formation and variations of mixed marine, tidal, and fluvial influences. The northernmost core (Norwich: ~120 m thick) contains more red, terrestrial paleosols and fluvially derived facies, whereas the southernmost core (Rich Valley: ~95 m thick) consists of an increased amount of facies with mixed tidal (mud-drapes, rhythmic lamination, syneresis cracks) and marine influences. Furthermore, regional correlation of key stratigraphic surfaces tied to both cores indicate the presence of a NW-SE trending mixed marine-tide sand-dominated interval with basal scouring and lateral pinch-outs over 15 km. These dissimilarities are likely indicative of lateral facies changes across depositional strike (NE-SW trend) during overall shoreline progradation to the NW, varying degrees of scouring by fluvial systems across depositional strike, and shifting focal points of sediment input and dispersal. As such, these in-depth facies and stratigraphic analyses provide a better understanding of shoreline dynamics during the Late Devonian, specifically with reconstructing shoreline advances and retreats in response to a mix of allogenic and autogenic forcing mechanisms.