The nature of the processes responsible for the deformation of the Earth crust are still poorly understood. Compressional orogens are some of the most studied geological features; yet, the exact nature of the mechanism that connects mantle convection, the driving force of all tectonic processes, to plate convergence in orogenic zones is not known.
Some argue that Rayleigh-Taylor instabilities developing in the mantle part of the lithosphere are the most likely mechanism causing shortening in the overlying crust; others argue that a subduction-like process is more likely; finally, others argue for a combination of both processes. In recent years, Braun has developed a two-dimensional model of lithospheric deformation driven by mantle subduction and/or gravitational instabilities. Coupled to a simple one-dimensional model of surface erosion and deposition, the model is able to make prediction on the Pressure-temperature- time paths of rocks, from which a range of geological observables can`predicted'.
Many hypotheses on the nature of the driving mechanism as well as on the rate of relative plate movement, the rheology of the lithosphere, its response to sedimentation, etc. can be tested with this model. We will use NA to invert large, multi-faceted geological datasets that exist on a variety of orogens, such as the Southern Alps of New Zealand or the Himalayas of central Asia.