Mesozoic halokinesis and basement inheritance in the eastern Provence fold-thrust belt, SE France

Abstract

The Provence Chain incorporated preexisting halokinetic and basement features which have played a key role in the structural evolution of the thrust systems. Field structural data, previously published geological maps and exploration well data have been used to interpret a new ~80 km-long balanced and restored cross section across the eastern Provence fold-thrust belt. The geological data and cross section construction suggest evidence for Mesozoic salt domes and minibasins embedded in the thin-skinned thrusts, and upper Paleozoic extensional structures transported on new thick-skinned thrusts. According to field data, pre-contractional palinspastic restoration suggests that salt domes and minibasins grew mainly during Rhaetien to late Jurassic times and intermittently until the early Santonian. Minibasins are mainly filled by carbonate systems associated with gravitational instabilities in minor normal faulting. Minibasin sinking into middle-upper Triassic evaporitic-carbonate succession has been mainly controlled by sediment loading. However, the initiation of salt movements might have been controlled by the initial geometry of the Triassic strata and probably extensional basement faulting. Preexisting salt structures have controlled thrust emplacements and their kinematics. Synorogenic deposits indicate a classical hinterland to foreland sequence of thrust inversion of the margin during the upper Cretaceous-Eocene Pyrenean-Provence compression. Diapiric structures were mainly eroded during and after the Pyrenean-Provence compression then reactivated during Oligocene extension and Miocene to present-day Alpine compression. Cross section balancing shows a total horizontal shortening of 28.5 km related to the Pyrenean-Provence and Alpine compressions. The eastern Provence fold-thrust belt integrates preexisting halokinetic folding which can be misinterpreted as resulting to compression. This suggests that a significant amount of folding in fold-thrust belts can results from an early halokinetic fold system developed during the pre-contractional passive margin evolution.