Sebastian Wolf

How to invert extensional basins – modelling the influence of pre-collisional extension on 3D mountain belt architecture

Sebastian Wolf

The geological record shows that many orogens, like the Andes, Pyrenees, Atlas, and Greater Caucasus form to a large degree by inversion of pre-collisional extensional basins that are typically offset and show different degrees of basin linkage. However, the 3D dynamics of inverting offset extensional basins and their importance for mountain building remain poorly understood. To bridge that knowledge gap, we use 3D state-of-the-art geodynamic models coupled to a fluvial surface processes model to investigate the dynamics of extensional-basin inversion during continent-continent collision. We find that a) basins link during the extensional stage if basin off-set is not too large; b) inversion of off-set rift basins naturally tends to create opposite polarity subduction, which reverts the plan-view structure of the mountain belt; c) same-polarity subduction requires further weaknesses, but preserves the structure of the extensional basins in the mountain belt. The distribution and orientation of topography and fluvial valleys tracks the deep-structure and can be used as indicators. Based on these model characteristcs and backed by a force-balance analysis, we compare the model results to the Pyrenees, Atlas, and Greater Caucasus.