Field-based 3D Modelling of a Growth Syncline :
The Annot Syncline, SE France
Cazaux, Adrien1,
Mary Ford2, Lise Salles3,
Christian Le Carlier de Veslud4, Antoine
Le Solleuz5 (1) IFP School, Rueil Malmaison, France (2) Nancy School of Geology, Nancy,
France (3) Nancy School of Geology, France, Vandoeuvre
lès Nancy, France (4) Nancy School of Geology, (5)
Nancy School of Geology, ENSG-G2R, Vandoeuvre-les-Nancy,
France
3D geomodelling
packages are currently not well adapted for the construction of 3D stratigraphic and structural models from spatially limited
data such as field data. Specific methodologies are developed for this task
within the gOcad geomodeller,
using multiple cross sections and pseudo-wells. A case study of the Annot Syncline in SE France is presented. The Annot Sandstone is one of the best-known analogs for sandy turbidites deposited in a compressional
thrust belt setting. The Bartonian to Rupelian succession is preserved as a series of
well-exposed outliers across SE France, remnants of sub-basins
within the alpine foreland basin. These exposures have been intensively studied
in terms of sedimentology and sequence stratigraphy. Their structural context is still however
problematic, involving both normal faults and active folds. The Annot Syncline preserves the complete foreland basin stratigraphy of transgressive Nummulitic Limestones, deep water
Globigerina Marls and basin-filling Annot Sandstone turbidites. A 3D model ( in gOcad), uses a DEM (50m resolution), geological map, stratigraphic and cross sectional data. 3D coherence of
thickness variations and throw across fault planes is used to test viability of
field-based interpretations of both growth folding and
faulting. The timing and role of folding is examined in 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.