A major conodont extinction event during the early Ordovician within the Midcontinent realm

Abstract

The major change in the Lower Ordovician conodont faunas of the Midcontinent Realm was recognized by earlier workers. Our recent intense study of Midcontinent conodonts from the St. George Group, Port au Port Peninsula, western Newfoundland, has shown that seven major conodont lineages, involving some 33 multielement species, completely terminate in the late Tremadoc Series, within an interval of a few metres, at a level between the Lower Ordovician conodont Fauna C and Fauna D. The extinction event occurs during the peak of a regressive phase within the deposition of the St. George Group and at a time of apparent global eustatic fall at or slightly below the Tremadoc-Arenig series boundary. This important extinction bioevent has been recognized throughout the Midcontinent Realm in North America.