Tectonic assembly of Gondwana

Abstract

The Paleozoic assembly of Pangea, with Gondwana as its southern half, completed the last full cycle of growth and dispersal of supercontinents during earth history. This assembly apparently resulted from reorganization of a preceding supercontinent (Rodinia) that existed at ∼1000 Ma. In addition to Laurentia and fragments that formed nuclei for Europe and Asia, the rifting of Rodinia produced: (1) East Gondwana, consisting largely of Western Australia, India, East Antarctica, and possibly part of southern Africa; and (2) various smaller fragments that converged to form West Gondwana, consisting of most of Africa and South America. East Gondwana appears to have been a stable block at a time no younger than ∼1000 Ma and possibly older. West Gondwana accreted largely in the latest Proterozoic and early Paleozoic by closure of the Pharusian Ocean in the north, the Adamaster Ocean in the south, and the ANEKT/Mozambique Ocean between West and East Gondwana. The assembly process was diachronous along numerous mobile belts, accompanied by syn- and post-collisional shearing and magmatism, and led to development of successor basins and rifts. Uncertainties in the timing and mechanism of assembly of Gondwana greatly limit our understanding of the supercontinent cycle. Thus, we propose investigations of Gondwana to determine more precisely the nature and age of apparent cratonic blocks, the locations and ages of orogenic belts, the configuration of former ocean basins, the significance of transcontinental shears, the extent of reactivation of older terranes, and the relationship of Gondwana to North America. Detailed knowledge of the assembly of Gondwana should also provide information on its relationship to other major processes such as mantle evolution and atmospheric, oceanic, and biologic changes.