Mesh-based tectonic reconstruction: Andean margin evolution since the Cretaceous

Tomas P. O'Kane, and Gordon S. Lister

In this contribution we demonstrate an example of what can be described as mesh-based tectonic reconstruction. This differs from conventional 2D + time reconstructions that treat the Earth as an assemblage of rigid plates. Instead a deformable mesh is overlaid on the region of interest, in this case the Andean margin of western South America, and allowed to deform based on constraints and assumptions inferred from geochronological and geological data. Here we take data that allows estimates of crustal shortening, and the timing of terrane accretion, to quantitatively estimate the starting geometry, from Early Cretaceous time (i.e. 145 Ma). Removal of strains straightens the Central and Southern Andean margin, and predicts the former existence of marginal basins to the east of the present mountain belt. This example of deformable mesh-based tectonic reconstruction illustrates the power of the method, incorporating such effects as simple isostasy, and the calculation of strain trajectories though time.