INTRODUCING THE BALSAMIAN, NEW SUBSTAGE OF THE EARLY CHATFIELDIAN (MOHAWKIAN, LATE ORDOVICIAN): CHRONOSTRATIGRAPHIC IMPLICATIONS OF THE GUTTENBERG δ 13C EXCURSION (GICE) IN NEW YORK STATE AND ONTARIO

The Balsamian has been proposed as a substage of the Chatfieldian Stage (Mohawkian, Late Ordovician) to replace the Rocklandian and Kirkfieldian standard stages (or substages) based on the nature of the Guttenberg δ¹³C Excursion (GICE) at the type sections of these standard stages. Previously, the GICE had been reported in many localities across the North American Midcontinent and Nevada, but has not been reported from localities in New York State and Ontario, where significant work on the standard classification of the Ordovician in North America has occurred. Detailed sampling of this stratigraphic interval from two sections in New York State (Dexter Quarry and Roaring Brook) and four sections in Ontario (Kirkfield Quarry, Rockland Quarry, Great La Cloche Island, and Hull Cement Quarry) for δ¹³C analysis has shown that the Rocklandian and Kirkfieldian are coeval. In all sections, revised conodont biostratigraphy is tied to the GICE curve. A composite GICE standard curve for New York has been defined for correlation with crucial successions in Kentucky, the Upper Mississippi Valley and Baltoscandia. The study corroborates the utility of δ¹³C chemostratigraphy for clarifying stratigraphic relationships.