EVOLVING ALPINE EDIFICE AND SEDIMENT PROVENANCE RECONSTRUCTED FROM THE HEAVY MINERAL ARCHIVE OF A THRUST-SHEET-TOP BASIN: THE BARRÊME BASIN, PROVENCE, FRANCE

The Tertiary thrust-sheet-top Barrême Basin is an excellent area in which to study the complex interplay of Alpine hinterland generation and linked foreland basin evolution. The basin is located in the external zones of the Provençal thrust belt in Alpes-de-Haute-Provence, in the hanging wall of the southwest-directed Digne thrust sheet. Such basins form during the early stages of shortening and provide an insight into the early structural and stratigraphic evolution of mountain belts. The basin fill is, therefore, an archive of key Alpine events, preserving their influence on landscape configuration, drainage patterns and sediment composition. Each of the 15 formations is characterized by distinctive heavy mineral suites and can be identified with a particular source province, including mature sedimentary sources, arc volcanics, crystalline rocks, HP Alpine metamorphics and ophiolites. They reveal the diversity and shift in source provinces as the Alpine landscape evolved, providing a unique record of the early structural and stratigraphic evolution of the mountain belt. The basin fill is 900 m thick, spans about 17 m.y., and evolved from an early flysch, to a subsequent molasse basin. Coarse-grained steep-fronted deltas represent the terminal marine fill of the basin, whereas the youngest formation, containing abundant immature orogenic detritus, records the out-of-sequence displacement and unroofing of the Embrun-Ubaye thrust sheets.