A NEW LOOK AT THE LITHOSTRATIGRAPHIC AND CHRONOSTRATIGRAPHIC CLASSIFICATION OF THE UPPER BLACK RIVER AND LOWER TRENTON GROUP OF CENTRAL PENNSYLVANIA

During a chemostratigraphic investigation of the lower Trenton Group (Mohawkian) in New York and Pennsylvania, the lithology of the two members of the Nealmont Formation were observed to share remarkable similarities between the overlying Salona Formation and underlying Linden Hall Formation of central Pennsylvania. Preliminary δ¹³C data suggested that the upper Nealmont, Salona and Coburn Formations did not correlate with the Trenton Group as previously thought. The question arises: is a separate Nealmont Formation necessary? To further examine these observations, chemostratigraphic, biostratigraphic and lithologic data from several sections in Pennsylvania were compared with data from the Black River and lower Trenton Groups of New York. Preliminary data from suggest that the Trenton Group of Pennsylvania is older than has been previously been recognized. Based on K-bentonite, δ¹³C and conodont data, the Nealmont Formation should be placed in the Turinian (= Blackriverian) stage and the lower Salona Formation should be placed in the Chatfieldian (= Rocklandian). Analysis of the lithological data suggests that the Centre Hall Member (lower Nealmont) is similar to underlying (typical) Black River strata, whereas the lithology of the overlying Rodman Member (upper Nealmont) is similar to the overlying Salona Formation and Trenton-style deposition.