2D Modelling of a fold and thrust belt in the French Prealps

Abstract

During this thesis, 2D modelling using the MOVE software suite is performed on a fold and thrust belt in the French Prealps. The area of interest is called the Couspeau area and is 72 km2. In this area, Vocontian basin sediments deposited during the Jurassic and Cretaceous can be found. The area contains well exposed fold and thrust structures. The oldest structures begin in the West, while the younger ones can be found in the East. All thrusts strike approximately N-S. These thrusts were assumed to be formed by the second Alpine orogeny. A structural map of the area was created in QGIS version 3.12.0 using geologic maps from the BRGM and using fieldwork data from Applied Earth Sciences students collected during the AESB2430 course at TU Delft. Subsequently, four E-W orientated cross sections of the area were constructed. These sections were restored using MOVE to verify if the interpretations were geologically feasible. 2D forward modelling was then applied to discover possible types of structural mechanisms which were active in this area. Possible mechanisms include fault-bend folding and regular folding. Fault propagation folding was assumed to be a suitable mechanism, but didn’t produce satisfactory forward models. Strain circles were added during forward modelling to analyse what kind of deformation is caused by different thrusting mechanisms. The restored sections were also used to calculate the total amount of shortening in the area, and how much of this shortening was caused by folding or faulting. The total amount of shortening was 24%, from which 38% was caused by faulting and 62% by folding.