Tectonic and paleogeographic significance of Late Ordovician conodonts in the Canadian Appalachians

Conodonts of Late Ordovician age are well represented in Laurentian parts of eastern Canada, but are rare in the Appalachian orogenic belt. They are known from the Anticosti Basin, the Matapedia Belt, and the Exploits Subzone of the Dunnage Zone. Two new discoveries are described: one from unnamed strata on Markey Brook, west-central New Brunswick, and one from the Goss Point Formation (Avalon Zone, southwestern New Brunswick). Faunas from the Anticosti Basin are of undoubted Midcontinent Faunal Region affinity. Those from the Matapedia Belt are highly mixed both paleoecologically and provincially, containing elements of shallow- and deep-water Midcontinent affinity and elements typical of the Atlantic Faunal Region. Faunas from the Exploits Subzone and Markey Brook are also mixed, suggesting endemic faunas of Atlantic affinity with local influx of Midcontinent faunas from Laurentia. The Goss Point Formation, previously believed to belong to the Mascarene Group (a Silurian cover sequence on the Avalon Zone), also yields mixed faunas. Provincial mixing of all faunas east of the Anticosti Basin suggests that Late Ordovician faunas around Iapetus Ocean may have been more homogeneous than earlier Ordovician faunas. Therefore, the Iapetus Ocean may have been smaller or current patterns may have changed to permit trans-Iapetan migration. A strong global pattern of provincialism for Late Ordovician conodonts is recognized and a new Australasian Province is proposed. Conodonts permit identification of a previously unrecognized Ordovician volcano-sedimentary succession that has economic and tectonic implications for the region.