PALEOZOIC LAURENTIA-GONDWANA INTERACTION AND THE ORIGIN OF THE APPALACHIAN-ANDEAN MOUNTAIN SYSTEM

Laurentia, the rift-bounded Precambrian nucleus of North America, may have broken out from a Neoproterozoic supercontinent between East and West Gondwana. Several lines of evidence suggest that the Appalachian margin of Laurentia subsequently collided with the proto-Andean margin of the amalgamated Gondwana supercontinent in different relative posi tions during early and mid-Paleozoic time, in route to final docking a gainst northwest Africa to complete the assembly of Pangea. Hence the Appalachian and Andean orogens may have originated as a single mountai n system. The overall hypothesis retains the same paleomagnetic and pa leobiogeographic controls as previous global reconstructions for the P aleozoic Era. Laurentia-Gondwana collisions may help to explain contem poraneous unconformities in the Paleozoic sedimentary cover of the Lau rentian, Gondwanan, and Baltic cratons.