St. George-Table Head Disconformity and Zinc Mineralization, Western Newfoundland

CIM Bulletin, 1968

L. M. CUMMING, Research Scientist, Crustal Geology Division, Geological Survey of Canada

The contact between dolomite of the St. George formation (Cambro-Ordovician) and limestone of the overlying Table Head formation (Middle Ordovician) is a regional disconformity. This is best illustrated from exposures on Pointe Riche Peninsula, near Table Point, and along Port au Port Bay. The contact occurs along 180 miles of the west coast of Newfoundland from St. John Island in the north to the western part of Port au Port Peninsula in the south. A disconformity of the same age occurs between the Romaine and Mingan formations on the north side of the Gulf of St. Lawrence. Dolomitic beds beneath the disconformity locally contain concentrations of base-metal sulphides. Sphalerite occurs in dolomite pseudobreccias of the St. George formation at Zinc Lake, 7 miles northeast of Daniels Harbour. The Western Newfoundland Lower-Middle Ordovician regional disconformity is interpreted as having originated on and near the edge of a broad platform, and to have provided an important regional geological control in the localization of zinc mineralization.
Keywords: Carbonate, carbonates, disconformity, dolomite, Northern Newfoundland, Ordovician, Port au Port Peninsula, dolomite, formation, limestone, Maps, Newfoundland, North, zinc