| Context: In various present-day regions, transpression is responsible for thickening and uplift of the crust (e.g. Puysegur Trench-Alpine Fault, South island, New Zealand; San Andreas Fault, Southern California). In most cases, it is not clear on the basis of available data whether convergence along the strike slip fault has evolved into steady state subduction of oceanic lithosphere with a significant strike slip component. Despite this fact, the geological evolution of transpression regions is often assumed to have occured due to subduction.The evolution from pure strike slip to mature oceanic subduction (if it ever occurs) is investigated following a change in relative motion from strike slip to transpression. Methods: Numerical simulations of the (thermo-)mechanical evolution of an ocean-continent plate boundary are used. Aim: 1) to identify in the numerical results observables that can be used to infer the stage of convergence in these regions, e.g. patterns of strain, horizontal and vertical motion, metamorphic grade and sediment distributions, 2) to determine the amount of normal convergence necessary to arrive at steady state subduction, and eventually, 3) to be able to better understand orogens that were formed in transpressional settings in the past, like the Alps or the Betic Cordillera. Present topics: The research is currently focussing on the effects of main control parameters such as buoyancy contrasts of oceanic and continental lithosphere, strength contrasts and geometry. |
