Modelling and visualising distributed crustal deformation of Australia and Zealandia using GPlates 2.0

Abstract

The recently released GPlates 2.0 software (www.gplates.org) provides a framework for building plate motion models including distributed extension and compression, driven by the motions of the surrounding rigid plate interiors, with constraints assimilated from well and seismic data. Here we present a regional deforming plate model for Australia and Zealandia. It captures the progressive extension of all Australian continental margins, starting with the Jurassic extension of the northwest shelf, and the Cretaceous extension of the southern and eastern Australian margins. The model also includes the extension of the Lord Howe Rise and southern Zealandia in the mid- to Late Cretaceous and the subsequent complex compressional deformation of New Zealand since the early Miocene. The model enables the time-dependent computation of crustal stretching factors for passive margins, as well as compression factors for orogenic regions. The thinning/thickening can be tracked by points distributed within a deforming mesh, either by starting with an assumed initial stretching factor or by applying an iterative approach in estimating initial crustal thicknesses to account for present-day constraints. The latter is suitable for basins, while the former is more applicable for orogens, where the present-day crustal thickness is not a reliable indicator of total crustal thickening due to the effects of erosion. Modelled crustal stretching factors can also be ground-truthed with independently derived stretching factors from strain rate inversion of stratigraphic sequences from well data or forward models of tectonic subsidence. The model can be combined with estimates of mantle-driven dynamic topography through time to generate basement subsidence or uplift models that include isostatic and dynamic components, serving as boundary conditions for basin and source-to-sink sediment transport models to provide improved constraints for resource exploration.