Does the Nealmont Formation Belong in the Trenton Group of Central Pennsylvania?

Barta, Nathanael C.
Department of Geological Sciences, The Ohio State University, Columbus, OH

Correlation and assignment of the Nealmont Formation within the Trenton Group (Mohawkian) of central Pennsylvania has varied during the past century and remains problematic. In the past, the correlation problem has been caused by poor descriptions, the transitional nature of the formation’s members and shelly-fossil correlations. Early correlations equated the Nealmont Formation with the Lowville and Watertown Limestones (Black River Group) in New York based on the similar gray to tan lime mudstone-wackestone lithology and typical “Black River” fossils. Later, G. M. Kay correlated the Nealmont Formation with the lower Trenton of the Kirkfieldian (= Chatfieldian) stage.

Recent observations during a chemostratigraphic investigation of the Salona and Coburn Formations in central Pennsylvania and the lower Trenton Group of New York suggest that the Nealmont Formation may not fully correlate, either lithologically or stratigraphically, with the Trenton Group as generally understood. To address this problem, lithologic, biostratigraphic, and chemostratigraphic data from the Nealmont Formation are compared with data from Black River and lower Trenton of New York.

Preliminary data suggest that the lithology of the Centre Hall Member is similar to Black River strata, whereas the lithology of the overlying Rodman Member is transitional into (more reminiscent of) Salona-style (Trenton) deposition. Based on K-bentonite, *¹³C and conodont data, the Nealmont Formation should be placed in the Turinian (= Blackriverian) stage.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004