REVISITING THE CAPROCK CARBONATE STRATIGRAPHIC NOMENCLATURE OF THE NIAGARA ESCARPMENT – GUELPH, ERAMOSA, AND AMABEL FORMATIONS, SOUTHWESTERN ONTARIO

This study builds upon the regional-scale surface and subsurface stratigraphic studies of the Silurian-age Guelph, Eramosa and Amabel lithologic units that have been carried out over the past century by providing insights into the many sedimentologic, stratigraphic and diagenetic features that are presently poorly understood. The study forms an integral part of the regional-scale industrial minerals/geochemistry inventories of these economically significant Silurian carbonates being carried out by the Ontario Geological Survey (OGS). Despite more than 150 years of study, the relative ages, stratigraphic relationships, and depositional environments of these key oil and gas- and industrial minerals-producing and aquifer-bearing formations are still poorly constrained. Emphasis will be on the highly variable lithofacies which make up the Eramosa rock unit, which has been 1) given the rank of beds of the uppermost Lockport Formation; 2) allocated formational rank (without designating a type section); 3) referred to as the upper member of the Lockport and Amabel formations; and 4) assigned the basal member of the Guelph Formation. Data from recently acquired drill cores have been integrated with regional-scale GIS-based mapping along the Ontario portion of the Niagara Escarpment to enable better correlations between traditional Lockport lithofacies and the Amabel Formation, and the overlying Eramosa and Guelph lithofacies throughout southwestern Ontario.