Barrandegnathus n. gen. (conodonta) from the Komstad Limestone (lower Mid Ordovician), Scandinavia, and its palaeogeographical significance

Abstract

A characteristic early Mid Ordovician conodont fauna first recorded from Bohemia is known from Morocco and southwestern Scandinavia. It is characterized by Barrandegnathus n. gen. (type species: Baltoniodus bohemicus Dzik, 1983). Barrandegnathus bohemicus is considered to be endemic to the Tornquist Sea, but it is often associated with Baltic Province conodonts. The fauna was first described from the Klabava Formation the sediments of which accumulated in the Prague Basin, Czech Republic and was subsequently recorded as reworked Ordovician conodont fauna preserved in Upper Silurian strata from Morocco and from the Komstad Limestone in southwest Scandinavia. The stratigraphical range of the species is confined to the late part of the early Mid Ordovician (Darriwilian; Volkhov Regional Stage). Barrandegnathus bohemicus probably migrated to Baltica with cold-water ocean currents moving from the high latitudinal Perunica terrane to the Gondwana supercontinent and to the southwestern margin of the Baltica continent. Baltic Province conodonts are recorded from cool-water carbonates at or just off the periphery of Gondwana. Rifting along the Gondwana margin followed by drifting of palaeocontinents and terranes towards mid-high latitudes promoted deposition of cool-water carbonates. Baltic Province conodonts are recorded from Gondwana and Gondwana derived continents. The distribution of cool-water carbonates and the associated conodont fauna shows that Baltic Province conodonts were not confined to the Baltica continent. Barrandegnathus n. gen. is introduced; the genus is represented by B. bohemicus (Dzik, 1983).