[1] The Flinders Ranges form one of the most seismically active zones within the Australian continent with seismogenic strain rates over the last 30 years of $10 À16 s À1 . Active deformation in the region reflects late Neogene increases in stress levels in the Indo-Australian plate as a response to increased plate boundary forcing from collision zones with the neighboring Asian and Pacific plates. Geological and geophysical observations suggest two modes of active deformation in operation in the Flinders Ranges over the last several million years: (1) . Numerical models are developed to explore the contribution of each of these deformation modes to the observed geophysical signals. An elastic mode of deformation is suggested by a distinctive longwavelength positive correlation between gravity and topography in which the Flinders Ranges are bordered by anomalous topographic and gravity lows, now occupied by playa-lake systems, centered some 50 km outboard of range-bounding faults. Numerical models show that flexural instabilities localized by vertical loads arising from older tectonic structuring produce a first-order match with observed topography and gravity. Numerical models are also used to illustrate how the localized failure evident in the contemporary seismicity and Quaternary faulting record within the Flinders Ranges reflects thermal weakening associated with extraordinary concentrations of heat producing elements in the crust, as reflected in modern-day heat flows of $90 mW m À2 .

During Late Cretaceous and Cenozoic times, many Palaeozoic and Mesozoic rifts and basin structures in the interior of the European continent underwent several phases of inversion (the process of shortening a previously extensional basin). The main phases occurred during the Late Cretaceous and Middle Palaeocene, and have been previously explained by pulses of compression, mainly from the Alpine orogen. Here we show that the main phases differed both in structural style and cause. The Cretaceous phase was characterized by narrow uplift zones, reverse activation of faults, crustal shortening, and the formation of asymmetric marginal troughs. In contrast, the Middle Palaeocene phase was characterized by dome-like uplift of a wider area with only mild fault movements, and formation of more distal and shallow marginal troughs. A simple flexural model explains how domal, secondary inversion follows inevitably from primary, convergence-related inversion on relaxation of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in the north-south convergence rate between Africa and Europe.

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