The geometry of a deformed carbonate slope‐basin transition: The Ventoux‐Lure fault zone, SE France

The Ventoux‐Lure fault zone (VLFZ) is a 70 km‐long, E–W trending triangle zone of folds and thrusts in the Alpine foreland of SE France. The VLFZ corresponds to the site of a Lower Cretaceous carbonate slope‐basin transition and it provides a good example of a deformed basin margin where, (1) compression was at a high angle to the basin margin; (2) deformation was mainly controlled by the mechanical stratigraphy and not by fault reactivation; and (3) inversion was a gradual process (from Middle Cretaceous) with deformation concentrated mainly in the basin to the north (as evidenced by growth strata) until the last (post‐Burdigalian) stages when the slope carbonates to the south were thrust northward on the Ventoux‐Lure Thrust (VLT). Within the eastern half of this zone structural geometries become increasingly complex from east to west, showing a progression from triangle zone to tectonic wedging geometries in which erosion of the emergent thrust sheets played an important role. This lateral variation was due to the obliquity of the eastern VLT to the Vocontian folds and the increase in displacement westward from a tip point south of Sisteron. The western sector of the VLFZ shows less N–S shortening and evidence of strike slip. On a regional scale, Late Cretaceous N–S shortening, contemporaneous with reactivation of NE–SW faults, may have been caused by the eastward migration of the Iberian‐Briançonnais plate to the south of the European plate. The post‐Burdigalian displacement of the VLT is correlated with the late Alpine SW emplacement on the Digne Thrust to the east. Within the French Alpine foreland the dextral NE–SW Durance Fault separated a zone where SW directed displacement was accommodated principally on the Digne Thrust from an area to the west, including the VLFZ, of more diffuse SW–NE shortening.