Vincent WICKER

MSC Project (Nancy School of Geology – ENSG)

Supervisors:
Prof. Mary Ford, ENSG and CRPG Nancy

Major Results

This work documents halokinesis within the Toulon Fault Zone (TFZ) in Eastern Provence, at the easternmost termination of the Pyreanean-Provencal orogenic system. A new salt-related structural model of the TFZ is proposed and integrates the inversion of the TFZ at the transition between Apto-Albian rifting and Pyreanean-Provencal convergence.

Abstract

The E-W Toulon Belt in eastern Provence records Aptian-Albian oblique rifting to Late Cretaceous Pyrenean-Provençal shortening. Relics of the easternmost Apto-Albian Pyrenean rift system are preserved as narrow inverted basins along the northern margin of the Toulon Belt. We present an updated structural interpretation of the eastern Toulon Belt with emphasis on the Mont Caume area, where we document continuous deformation due to salt tectonics from Jurassic to Late-Cretaceous. We then reexamine the better-known western Toulon fault zone and discuss the regional significance of the Toulon fault zone for Cretaceous to Cenozoic paleogeographic reconstructions.

Our field observations are integrated in a salt-tectonic model where the role of the salt deformation is predominant and continuous from early-Jurassic to Santonian times. Mini-basins and halokinetic sequences are observed in the eastern Toulon Belt (Mont Caume, Cap Gros, Mont Faron) surrounded by salt diapirs or salt welds.

The Mont Caume overturned structure is interpreted as a flap on the northern side of a salt diapir that grew from Early-Jurassic to Late-Cretaceous as recorded by growth strata in the Mont Caume minibasin preserved on the southern flank of the Beausset syncline. Important E-W sediment thickness variations with progressive unconformities along this flank are linked to salt mobility. Further west, the overturned Beausset klippe can be interpreted as the remnant of a flap on the northern flank of the Bandol diapir. The Toulon belt salt structures are excellent field analogues to others observed in the external Alps such as in Digne area.

This model also integrates the Aptian-Albian pyrenean fault zone and the timing of its structural inversion. Stratigraphic signals in the Mont Caume area may indicate onset of Pyrenean orogenic convergence in Eastern Provence in the Early-Middle Coniacian transition. Paleogeographic reconstruction show that the Turonian to Coniacian clastic sediments that infill the Mont Caume mini-basin came from an emerged massif in the east of Toulon area and that westward sediment routing was constrained by salt wall growth.

Structural model for Mont Caume Area, Eastern Toulon Fault Zone.