How hard were the Jura mountains pushed?

Abstract

The mechanical twinning of calcite is believed to record past differential stress values, but validating results in the context of past tectonic situations has been rarely attempted. Using assumptions of linear gradients of stress components with depth, a stress gradient based on twinning palaeopiezometry is derived for the Swiss Molasse Basin, the indenter region to the Jura fold and thrust belt. When integrated into a model of the retrodeformed Jura-Molasse system, allowing horizontal stress concentration and conservation along the original taper geometry, the stress profile proves consistent with the position of the Jura-Molasse (ftb-indenter) transition. The model demonstrates mechanically why the Plateau Molasse portion of the Molasse Basin remained relatively undeformed when transmitting tectonic forces applied to the Jura mountains.