Stretch and fold: Multistage analogue experiments of rifting, inversion, and orogenesis

Analogue models are powerful tools for investigating extensional and convergent tectonic processes in 4D and at multiple scales. However, rarely do we introduce two successive phases of tectonism in a single analogue experiment to study the interaction between structures from two kinematically distinct tectonic events. Here we showcase a series of analogue experiments in which lithospheric-scale models are extended and subsequently shortened, simulating rifting followed by inversion and mountain building.

In our experiments, we simulate rifting by extending a multi-layer, brittle-ductile model lithosphere; this initial model is analogous to a hot, thickened lithosphere immediately after orogenesis. We demonstrate that the absence or presence of a narrow, pre-existing weakness in the lithospheric mantle results in end-member models of either wide or narrow rifting, respectively. Extension is immediately followed by shortening of the model, where we observe that contractional structures are localised along pre-existing rift basins. Analyses of particle imaging velocimetry (PIV) data reveal that shortening is accommodated by several mechanisms, including reverse reactivation of normal faults and buckling and/or inversion within pre-existing basins. We also show that these findings are consistent with field and geophysical observations from northern Australia as well as previous numerical experiments.