A reassessment of paleogeographic reconstructions of eastern Gondwana: Bringing geology back into the equation

In recent years several tectonic reconstructions have been presented for Australia–Antarctica break-up, with each putting the Australian plate in a different location with respect to Antarctica. These differences reflect the different datasets and techniques employed to create a particular reconstruction. Here we show that some of the more recent reconstructions proposed for Australia–Antarctica break-up are inconsistent with both our current knowledge of margin evolution as well as the inferred match in basement terranes on the two opposing conjugate margins. We also show how these incorrect reconstructions influence the fit of the Indian plate against Antarctica if its movement is tied to the Australian plate. Such errors can have a major influence on the tectonic models of other parts of the world. In this case, we show how the position of the Australia plate can predetermine the extent of Greater India, which is (rightly or wrongly) used by many as a constraint in determining the timing of India–Asia, or India–Island Arc collisions during the closure of Tethys. We also discuss the timing of Australia–Antarctica break-up, and which linear magnetic features are a product of symmetric sea-floor spreading versus those linear magnetic features that result from rifting of a margin. The 46 Ma to 84 Ma rotational poles previously proposed for Australia–Antarctica break-up, and confined to transitional crust and the continent–ocean transition zone, more likely formed during earlier stages of rifting rather than during symmetric sea-floor spreading of oceanic crust. So rotation poles that have been derived from magnetic anomalies in such regions cannot be used as input in a plate reconstruction. A new reconstruction of the Australia–Antarctica margin is therefore proposed that remains faithful to the best available geological and geophysical data.