Late Ediacaran paleogeography of Avalonia and the Cambrian assembly of West Gondwana

Abstract

The latest Proterozoic tectonic evolution of Avalonia, one of the largest peri-Gondwanan terranes, bears on the issue of Gondwana amalgamation during the transition from Rodinia to Pangea. New paleomagnetic results from mid–late Ediacaran strata in the Newfoundland sector of Avalonia confirm substantial apparent motion of that terrane between ca. 590 and 560 Ma, consistent with a true polar wander interpretation for that interval. When the Avalonian poles are mapped onto complementary paleomagnetic records from West Africa and Laurentia, the Avalonia terrane may occupy any of four possible positions, all of which are far-removed from those cratons. Choosing the most kinematically parsimonious location leading toward Gondwana assembly, we find that Avalonia was most likely proximal to Amazonia during the Ediacaran–Cambrian transition, with a substantial (∼3000 km) separation between Amazonia and West Africa at that time. Our results thus favor the existence of a wide Clymene Ocean and subsequent Cambrian final assembly of West Gondwana, providing a key snapshot onto the evolving Rodinia-Gondwana supercontinental transition.