A thin-plate model of Palaeozoic deformation of the Australian lithosphere: implications for understanding the dynamics of intracratonic deformation

Presented here are the results of a thin-plate model of the continental lithosphere in which deformation is driven by velocities specified along the plate boundaries. The geometry of the model, the strength of each lithospheric block, and the boundary conditions have been chosen to reproduce the major tectonic episodes experienced by the Australian continent during a 200 Ma time period starting in the Ordovician (i.e. 470 Ma). The model's focus is on the reactivation and/or reworking of zones of weakness within the continent that have either been set a priori or developed in response to previous tectonic regimes. Using the tectonic history of the Australian continent as a natural laboratory in which hypotheses on the nature and style of intracratonic deformation can be tested, the following conclusions can be made: (i) intracratonic deformation results from the concentration of strain into regions of decreased lithospheric strength; these weak zones are often caused by previous intracratonic deformation and/or develop at the interface between regions of contrasting strength; (ii) repeated deformation episodes lead to strain localization; (iii) localized deformation may also take place as the result of the constructive interaction between two tectonic regimes originating on separate margins; and (iv) there are mechanisms that operate within the lithosphere by which deformation leads to local strengthening.