Staircase normal fault geometry in the Gr~s d'Annot (SE France)

Abstract: A normal fault geometry is observed in the sediments of the Gr6s d'Annot Formation. The sediments are deep-water siliciclastic deposits composed of mud-rich and sand-rich successions. This seismic- to sub-seismic scale fault system is considered as a good analogue for syntectonic basin infilling. The outcropping Gr6s d'Annot Formation allows small- to large-scale fault analysis coupled with stratigraphic analysis. The major faults, which have throws ranging from a few metres to hundreds of metres, belong to a tilted block succession. The mud-rich and sand-rich beds thickness range from a few centi-metres to tens of metres. The characterization f the fault system and the kinematic analysis carried out show strong correlation between fault geometry and lithological discontinuities. The fault geometry is largely controlled by the rheoiogical coupling between the mud-rich and sand-rich succession. Downdip displacement of fault blocks is accommodated by layer-parallel movement. Graben structures and synthetic fault sets are related to small-scale fault steps. The fault zone characteristics are related to these fault profile heterogene-ities. Kinematic analysis of this fault system provides tools for the characterization f stress field perturbation i a multi-layer system and its consequences in terms of strain localization and hydrodynamic behaviour. A good understanding of seismic-scale normal fault geometry is crucial to enable geologists to constrain basin evolution (Brun & Choukroun