The peri-Alpine Paleogene Red Molasse of southeastern France -

II. Faucon-du-Caire/Turriers area (Alpes de Haute Provence)

Abstract

The SW-NE-trending Faucon-du-Caire/Turriers tectonic corridor hosts a thick Paleogene Molasse Rouge s.l. succession that shows similarities to the same interval found in the nearby Esparron syncline. In each setting, the succession is composed of three superposed sequences designated S1, S2 and S3 from bottom to top respectively (Ferry et al., 2025). Although similar in internal character, they vary in thickness between the two localities with respect to both complete sequences and subunits. Sequence S1 represents the western shore of a continental basin oriented to the Alpine Mountain Belt. Deposits of sequence S2 (Molasse Rouge 1, or MR1) are confined to a valley that forms a westward continuation of the Esparron syncline, terminating against the Grand Vallon fault, which caused a shift of the river to the southwest where its exits the Digne transported basin. Downstream, its course likely followed the front of the Ventoux-Lure thrust. Deposits of sequence S3 (Molasse Rouge 2, or MR2) are up to 500 m thick in the Faucon-du-Caire/Turriers area, comprising a lower pebbly facies, around 200 m thick, that was formed by a braided fluvial system. This is overlain by reddish sandstone-dominated alluvial fan deposits approximately 300 m thick. Sequence S3 appears to be mostly constrained to the Faucon-Turriers corridor. Its materials were transported to the SW, exiting the Digne nappe along the front of the Ventoux-Lure thrust. This path is better documented than that of MR1. A first major point is confirmation that a major change in paleocurrent orientation occurred around the Rupelian-Chattian transition, with the deposits of upper Rupelian sequence S1 being oriented to the Alps, and those of the Chattian sequences S2 and S3 oriented the opposite direction to the west. A second point is that strong tectonic deformation occurred between the deposition of MR1 and MR2.