Restoring the continent-ocean boundary: constraints from lithospheric stretching grids and tectonic reconstructions

Abstract

We present a revised set of Euler poles describing the relative motion between Australia and Antarctica from the onset of continental rifting at ~160-140 Ma to the reorganisation of the spreading system at ~50 Ma. Our revised reconstruction addresses two key issues that remain unresolved in current plate reconstructions. Firstly, we present new estimates of the pre-rift plate boundary locations for the conjugate Australian-Antarctic margins. These reconstructions are truly palinspastic, incorporating estimates of crustal thickness along these margins, derived from gravity inversions. Integrating the crustal thickness along tectonic flowlines results in the pre-rift location of the continental plate boundary. This integration relies on defining the present-day extent of stretched continental crust within the margin, which is the subject of the companion paper, Williams et al. [2010]. Once restored, we are then able to use the pre-rift plate boundary positions to compute ?full-fit? poles of rotation for Australia relative to Antarctica. This approach allows us to model a deforming passive margin, with implications for understanding and modelling the formation of basins and deposition of sediments along passive margins. Secondly, reconstructions for plate motions since ~83 Ma have been revised to obtain a better fit along the entire Australian-Antarctic conjugate margins, which extend from at least the Kerguelen Plateau and Broken Ridge in the west to Tasmania, Australia and Cape Adare, Antarctica in the east. Previously published reconstruction models for the period 83-50 Ma had resulted in a poor fit between the two plates at the extreme ends of the conjugate margins.