CAMBRIAN-ORDOVICIAN PALEOGEOGRAPHY OF BALTICA

Recent paleomagnetic data and existing paleontological evidence show that Baltica occupied temperate southern latitudes during Cambrian and Early Ordovician time, but was inverted with reference to its present orientation. Hence the currently opposed margins of the Baltic and Laurentian shield were not conterminous in the early Paleozoic. Laurentian and Baltic late Precambrian rifting episodes may therefore have occurred along unrelated continental margins. Closure of the Tornquist sea was accompanied by the counterclockwise rotation of Baltica relative to Avalonia in Early to Middle Ordovician time. This rotation, initiated in Late Cambrian-Early Ordovician time, was coeval with the Finnmarkian orogeny in the northern Scandinavian Caledonides.