CONODONT PALEOECOLOGY OF THE LOWER ORDOVICIAN ST-GEORGE GROUP, PORT AU PORT PENINSULA, WESTERN NEWFOUNDLAND

The St. George Group in western Newfoundland is nearly 600 m thick and is subdivided into the Watts Bight, Boat Harbour, Catoche, and Aguath una Formations. The group is a nearly complete Lower Ordovician succes sion representing about 15-20 m.y. The depositional environment of the St. George Group is represented by three main lithofacies (supratidal , peritidal, and subtidal), expressed as two first-order cycles and fi ve second-order cycles. In the study of St. George Group conodonts, ov er 70 multielement species are represented in 45,000 conodont specimen s from 432 samples of 10 sections. Computer cluster analysis of most o f those samples on the basis of similarity of conodont species was use d to determine conodont community structure. Both the principal coordi nate analysis (PCA) partitioning method and the agglomerative method ( UPGMA with Bray-Curtis) were chosen for the statistical analysis. The four lithological formations and five secondary lithological cycles in the St. George Group emerge as distinct entities when the samples are clustered together on the basis of conodont data for analysis of firs t-order and second-order variations in community composition. Two deep er water, five shallow-water, and five intermediate communities throug h this time interval are recognized. The majority of conodonts from th ese communities are of Midcontinent Realm affinities, but some species represent strong North Atlantic Realm influxes during the transgressi ve periods.