The main goal of this study is a better knowledge of the deformation and sedimentary evolution of the southwestern part of the Paris basin, a low subsiding domain, at the transition between the Paris and Aquitaine basins. This study is based on the analysis of industrial seismic lines reprocessed by the BRGM (French Geological Survey), calibrated on petroleum wells, water supply wells (coming from the BSS, BRGM database) and outcrops.
Four second order (10 Ma and multiples) transgressive-regressive cycles were defined on facies evolution on dated sediments. There are similar to those defined in the central part of the Paris basin, with some differences on the age limits. Seven seismic units, bounded by time-lines, were mapped. Isopach map and wells correlations show four main results. (1) The Mid-Cimmerian (Toarcian-Aalenian) and Neo-Cimmerian (Berriasian) medium to long wavelength deformations are well recorded (with truncations) in this area. (2) Two main phases of extension, contemporaneous with the Tethys Alpine rift, of Early to Middle Liassic and Early Bajocian ages were characterized. The first one was mapped at the scale of France. (3) A medium to long wavelength flexural subsidence regime, initiated during Bathonian, occurred during Callovian to Oxfordian times, contemporaneous with the progradation of a carbonate platform toward the SSW. (4) Some major basement faults were active during all the Jurassic whatever the type of subsidence.