Significance of Conodonts, Graptolites, and Shelly Faunas from the Ordovician of Western and North-Central Newfoundland

Abstract

Numerous collections of graptolites, conodonts, and shelly fossils provide new information about the age of several previously imprecisely dated formations on Newfoundland. The Long Point Formation is raised to group rank with two new formations, the Lourdes Limestone and the Winterhouse Formation. The Lourdes is largely Porterfieldian, indicating a pre-Nemagraptus gracilis Zone age for the Bonnian phase of the Taconian orogeny. In northern Newfoundland, the Nemagraptus gracilis Zone has been identified in the Lawrence Harbour Shale, and in shales along the Trans-Canada highway; the Diplograptus multidens Zone in argillites at the base of the Point Leamington Greywacke; the Dicranograptus clingani Zone in the same argillites, shales east of Gander Bay, the Rodgers Cove Shale, the Dark Hole Formation, and unit C of the Summerford Group; and the Pleurograptus linearis Zone in the Point Leamington Greywacke, unit C of the Summerford Group and the Rodgers Cove Shale. The Pygodus anserinus and Pygodus serrus conodont zones are present in the Cobbs Arm Limestone and the latter zone in the Summerford Group. The Cobbs Arm Limestone and the Rodgers Cove Shale (new) are referred to the Hillgrade Group. The conodont and graptolite faunas from north-central Newfoundland are of 'European' rather than 'North American' type, but the conodont and graptolite faunal provinces do not have the same regional distribution in eastern North America.