Australo-Antarctica in Gondwana: a view from the edge

Plate reconstructions that consider Neoproterozoic (770-750 Ma) paleomagnetic data from India and Australia imply significant (∼3000-5000 km) relative displacement between these continents before they reached their unified Gondwana fit by ∼540 Ma (Fig. 1; e.g., Li et al., 2013). Therefore, these models require a plate boundary (or boundaries) between Neoproterozoic India and Australia, with or without accreted terranes that may have been in between. The inferred plate boundary must also penetrate East Antarctica, separating the Indo-Antarctic and Australo-Antarctic blocks. However, there is considerable flexibility around the magnitude of displacement, as well as the nature of the motion, depending on: (1) the Euler pole selected using the 95% confidence level ellipses of the paleomagnetic data, and (2) the location and geometry of the plate boundary. These constraints have implications for the width of a pre-Gondwanan ocean basin between Indo-Antarctica and Australo-Antarctica, the timing of collision along the margin, and the tectonic style expected to be recorded in the rocks.