EVIDENCE FOR MULTIPLE SEA-LEVEL INCURSIONS WITHIN THE UPPER DEVONIAN CATSKILL FORMATION, CAMERON AND MCKEAN COUNTIES, NORTH-CENTRAL PENNSYLVANIA

Within the Upper Devonian Catskill Formation and equivalent units in New York, Pennsylvania, and West Virginia, previous analyses have broadly focused on depositional environment interpretations. Current literature defines the Catskill Formation as a mixture of terrestrial, coastal plain, and shallow marine deposits that prograded westward into the Appalachian Basin from the Acadian Highlands. Additionally, studies address the general, broad-scale stratigraphy of the Catskill Formation. However, a need still clearly exists for the development of a stratigraphic framework in order to fully understand the depositional history of the Catskill. In this study, the sedimentological and stratigraphic relationships of paralic and terrestrial facies are considered in two drillcores, newly acquired by the Pennsylvania Geological Survey, from Cameron and McKean counties. Also, wireline logs from > 50 locations in northcentral Pennsylvania have facilitated the assessment of the regional stratigraphy and distribution of depositional facies, both parallel and perpendicular to a north-northeast trending Upper Devonian regional shoreline. In core, the Catskill Formation (114 – 123 m thick) is largely comprised of terrestrial environment facies, including arid coastal plain and fluvial lithologies. More importantly, several (3-4) intervals of marine to brackish-water facies alternate with terrestrial facies and contain similarities to estuarine or incised valley fill deposits of the Catskill Formation from central Pennsylvania (e.g. Cotter & Driese, 1998). The alternating marine, brackish-water, and terrestrial facies stacking patterns are found in the bottom 60 m and upper 20 m of the Catskill Formation, which is indicative of temporally short sea-level fluctuations impacting the Catskill shoreline. Furthermore, these shorter-term cycles appear to be nestled within a longer-term shoreline progradation-retrogradation trend encompassing the entire Catskill Formation. Through this study, newly obtained cores and wireline logs have provided an excellent opportunity to build upon previous interpretations by understanding the deposition of the Catskill Formation within a stratigraphic context, potentially on both local and regional scales throughout the Appalachian Basin.