NEOPROTEROZOIC - EARLY PALEOZOIC EVOLUTION OF PERI-GONDWANAN TERRANES AND IMPLICATIONS FOR LAURENTIA-GONDWANA CONNECTIONS

Neoproterozoic tectonics is dominated by the amalgamation of the supercontinent Rodinia at ca. 1.1 Ga, its breakup at ca. 0.75 Ga and collision between East and West Gondwana between 0.6 and 0.5 Ga. The principal stages in this evolution are recorded by the so-called peri-Gondwanan terranes along the northern margin of West Gondwana (Amazonia and West Africa), which continuously faced open oceans during the Neoproterozoic. There are three types of terranes that were distributed along this margin in the late Neoproterozoic (i) Avalonian-type terranes (e.g. West Avalonia, East Avalonia, Carolina, Moravia-Silesia, Rhenohercynia) that originated from ca. 1.2 to 1.0 Ga juvenile crust (oceanic arcs and plateaus) within a Panthalassa-type ocean that surrounded Rodinia and became accreted to the Amazonian portion of the Gondwanan margin by 650 Ma. (ii) Cadomian-type terranes (Armorica, Ossa Morena, Saxo-Thuringia, Perunica) formed along the West African margin by recycling ancient West African crust and (iii) Middle America terranes (e.g. Ouxaquia, Chortis) that originated along the Amazonian margin and recycled Amazonian crust. These terranes became detached from Gondwana and are now located within the Appalachian, Caledonide and Variscan orogens of North America and western Europe. The inferred relationships between these peri-Gondwanan terranes and the northern Gondwanan margin are compared with paleomagnetically constrained movements interpreted for the Amazonian and West African cratons of Gondwana from ca. 800-500 Ma. As Amazonia and West Africa are unconstrained paleomagnetically during this interval, and the location of Amazonia is deduced from an interpreted connection with Laurentia, such an analysis has implications for Laurentia-Gondwana connections and for high latitude versus low latitude models for Laurentia at around 570 Ma. The available paleomagnetic data from both West and East Avalonia, show systematically lower paleolatitudes than predicted by these models. This implies that either Laurentia had a more complicated movement history between 720 and 615 Ma than is currently constrained by the available data, or the configuration of Laurentia and West Gondwana on many Neoproterozoic reconstructions is incorrect.