Control of inheritance, crustal strength and relative rate of extrusion/indentation on 3D strain distribution and basin reactivation: insights from laboratory models

Cases where multiple tectonic regimes acted closely in space and time have been long recognized. The coexistence of thrust, strike-slip, and normal faulting has been documented in thick orogenic regions, in oblique convergent settings associated with strain partitioning, in areas of indentation tectonics and lateral escape, and synorogenic foreland rifting/transtension settings, where extension-transtension takes place in close spatiotemporal relation with plate-margin shortening. Here, we use analogue models to test how parameters like the crustal strength, basement inheritances, and relative rate of extrusion/indentation can be effective mechanisms to explain the coeval emplacement of thrust, strike-slip, and normal faults. We also investigate their effect on fault reactivation in previously extended basins.

We show that a strong crust can exhibit coeval thrust faults, strike-slip faults and normal faults for ratios of extrusion over indentation rates in between 1.4 and 2, as orientation and magitude of principal stresses spatially vary within the model. For a weaker crust, normal faults and thrusts faults cannot coexist at the same time. Inheritance, which is implemented through the presence of a seed simulating a preexisting weakness zone or through an initial phase of extension, controls the geometry of strike-slip faults, whose orientation departs from the Coulomb fracture criterion. Reactivation of former normal faults as normal faults is only possible for ratios of extrusion over indentation rates over 1, for both weak and strong crusts. For lower rates, pre-existing normal faults are reactivated as indentation-parallel strike-slip faults. Our experimental results are then compared with the tectonic evolution of the Eastern Anatolia, the Alps and the Central Patagonia.