History and deformation rates of a thrust sheet top basin: the Barreme basin, western Alps, SE France.

The geometrical evolution of the 2 km wide Barrême thrust-sheet-top basin has been established over a time interval of 10 Ma. The Barrême basin developed during the late Eocene-Oligocene, during the migration from east to west of the western Alpine orogenic front in SE France. Unlike in other orogenic belts, where foreland basins are often buried and observable only on seismic profiles, the outcrop conditions at Barrême allow the detailed analysis of this basin fragment. The syntectonic sedimentation and growth strata preserved on the east flank of the Barrême basin, on the Clumanc Anticline, are used to restore sequentially a balanced cross-section, thereby constraining the progressive steps of basin development. Numerical ages, obtained by correlating biozones and chronostratigraphy with most recent geochronological calibrations, are assigned to the bases of the mappable growth strata in order to obtain an indication of deformation rates. Shortening rates vary from 0.003 to 0.2 (±0.083) mm a−1, while uplift rates vary from 0 to 0.37 mm a−1. These rates are comparable to those recorded in recently active mountain belts, and represent a significant refinement of previously published rates for the Barrême basin.