Odyssey of terranes in the Iapetus and Rheic oceans during the Paleozoic

Abstract

Geologic, paleomagnetic, and faunal data indicate that Paleozoic terranes bordering the Iapetus and Rheic oceans may be classified as native or exotic with respect to adjacent cratons. Native terranes include the Notre Dame-Shelburne Falls arc lying along the eastern margin of Laurentia, Cadomia situated adjacent to North Africa, and the Famatina, Puna and Arequipa-Antofalla Terranes occurring adjacent to western South America. Exotic terranes include the western South American terranes, Cuyania and Chilenia, which are inferred to have been derived from southern Laurentia; and the North American terranes, Oaxaquia, Florida, Carolina, Avalonia, and associated terranes, which have a Gondwanan provenance in northern South America-West Africa. Early Cambrian opening of Iapetus was followed in Late Cambrian-Early Ordovician by extensional subduction that produced volcanic arcs and backarc basins on both margins (Notre Dame-Shelburne Falls and Famatinian arcs), which changed to compressional arcs collapsing the backarc basins during the mid-Late Ordovician. During the Ordovician, Cuyania was transferred from southern Laurentia to western Gondwana, and Carolina/Piedmont and Avalonia moved from northwestern Gondwana to eastern Laurentia. This exchange indicates that the southern part of Iapetus was preferentially subducted beneath South America as the central part was mainly subducted beneath eastern Laurentia, and suggests that southern and central Iapetus were separated by a major transform fault. After the Late Ordovician demise of Iapetus, the Rheic ocean persisted between Laurentia and Gondwana, and terranes appear to have remained adjacent to their neighboring craton until the terminal amalgamation of Pangea in the Permo-Carboniferous. During the Mesozoic break-up of Pangea, the Oaxaquia, Chortis, Florida, and Cadomia Terranes were left adjacent to Laurentia and Baltica.