Impact of Halokinesis in a Foreland Basin, Aquitaine Basin, France: Contribution to the Study of Upper Cretaceous to Paleocene Reservoir Formations—Part I

Toullec, Renaud¹, Adrian Cerepi¹, Philippe Razin¹, Louis Humbert¹, Gildas Lageat², Nicolas Labat², Christophe Rigollet² (1) Université Michel de Montaigne Bordeaux III, Pessac, France (2) Gaz de France, Saint Denis La Plaine, France

This study intends to propose a numerical model suported by a preliminary seismic stratigraphy analysis of a south part of the aquitaine basin (the Adour Sub-basin). The aims of the study are to understand the cinematic of a foreland basin under halotectonic control and to predict reservoir/cover spatial distribution. The model is composed of six layers, Albian to Priabonian aged, well constrained and depth migrated with the integration of major discontinuities. The Picking of the six layers has been produced with a Charisma software and the modelisation with a Petrel software. The surveyed area is limited by Magesq and Sebastopol/Dax structures to the west and by Siougos and Audignon structures to the est. The Principal geological structures are N100-110 (anticlines) and N150-160 (strike-slip net­work) oriented. The development of anticlines (Magesq, Sebastopol/Dax, Louer, Thétieu, Audignon and Siougos structures) is related to the dampening of the pyrenean deformation northward by means of a thick triasic salt decollement level leaded by an important hercyn­ian heritage. Strike-slip network is materialized by the “Thétieu corridor” which could be due to a late orogenic pyrenean phase during oligocene. Thanks to this strike-slip network, tria­sic salt would have come back up illustrated by Thetieu cylindrical diapir “grafted” on the his broadest meridional part. Sedimentary dynamics is interpreted at two observations scales: -A regional scale where the deposit’s geometry is linked to “long wave tectonic” (subsidence and uplift), halocinese and major eustatic variations. -A local scale where diachronous grow­ing of diapirs at differents velocities explain the local geometry of reflectors.