3D Structural
Control of Turbidite Deposition in a Foreland Fold
and Thrust Belt: The Annot Sandstone Depocentre of Sanguinière, SE France
Salles, Lise1, Mary
Ford2, Antoine LeSolleuz3, Philippe Joseph4,
Christian Le Carlier de Veslud5 (1) Nancy
School of Geology, France, Vandoeuvre lès Nancy, France (2) Nancy School of Geology, France,
France (3) G2R, Nancy School of Geology, Nancy, France, France (4) Institut Francais du Petrole, 92852 Rueil Malmaison Cedex, France (5) Nancy School of Geology,
The Annot
Sandstone is a well-known analog for sand-rich deep-water reservoirs. The
succession was deposited in a deltaic setting over period of 10My from the Bartonian to Rupelian, in the
active alpine foreland basin. Today the Annot
Sandstone is superbly exposed in the subalpine
mountain chains of SE France. Detailed sedimentologic
and stratigraphic studies have been published on the Annot Sandstone, however,
structural controls on turbidite deposition are not
yet well constrained. A new field-based structural study is used to construct a
3D geometrical model (gOcad) of the Sanguinière depocentre, the
northernmost Annot sub-basin. This is one of the
best-known turbidite depocentres
and is generally believed to have developed above a growing syncline. However,
our work on the timing, kinematics and geometry of principal faults and folds
suggests that N-S normal faults played an important role in early depocentre evolution. 3D coherence of throw across fault
planes for different stratigraphic reference horizons
is used to test the viability of field-based interpretations of growth faulting
and folding. The modelled horizons correspond to the
base of the Tertiary basin fill (base of Nummulitic
Limestone), the base of the Annot Sandstone itself
and three key horizons within the Annot Sandstone.
The timing and role of folding is studied from derived isopach
maps. The 3D model can therefore constrain components of deformation due to
faulting and folding and thus clarify the interaction of turbidites
with active structures in a foreland setting.