ALPINE DEFORMATION FROM THE INTERNAL AUSTRIAN TAUREN WINDOW NORTHWESTWARD TO THE BRITISH FORELAND AND IRISH TERTIARY PROVINCE

The north Atlantic Ocean opened ~58 Ma ago leaving marginal basaltic flows, dikes and sills with contemporaneous calcite-filled veins and fault striations. In northern Ireland, calcite is mechanically twinned up to 100 km inboard of the coast, and the calcite (n=16) preserves a margin-parallel, horizontal shortening strain and vertical extension with no strain overprint. Farther inboard to the southeast, across England, France and Germany, the younger Alpine orogen (~26 Ma) imparted a deformation regime dominated by SE-NW sub-horizontal shortening, preserved by mechanical twins in calcite in Mesozoic limestones and calcite veins (n=28), up to ~1000 km northwest from the Alps. Twinning studies in the frontal Jura Mountains (n=45; northwest) and molasse basin (n=19), Penninic flysch (n=22) and internal Helvetic nappes (n=42), and Tauren window (n=8; southeast) preserve a layer-parallel, SE-NW shortening strain that becomes increasingly complex with more strain overprint (higher NEVs) results and a more prevalent layer-normal shortening strain in the Alpine nappes.