UPPER CRETACEOUS PALEOGENE SEDIMENTARY RECORD OF THEPYRENEAN RETROFORELAND (AQUITAIN BASIN). DEFORMATIONSAND SEDIMENT DYNAMICS

International audienceThe southern foreland (proforeland) of the Pyrenean orogeny is one of the most well-known foreland inthe world, on the opposite its northern retroforeland (i.e the Aquitaine basin) which display a quite differenttectonic style is less documented apart from local petroleum studies. Strong efforts have been made in therecent years to improve the knowledge of the Pyrenean orogeny and Aquitaine basin. We present here asynthesis of the Aquitain basin evolution during Upper Cretaceous and Paleogene based on the integration ofmore than 1000 wells and 5000 km of seismic profiles. A harmonized and detailed litho-and sequencestratigraphy was build up for the entire period allowing to recompose large scale sections, thickness and faciesmap at the scale of 1 My, and sedimentary response to compressive deformation. The distribution, style andtiming of deformation of the retroforeland are precised thanks to refined stratigraphic constraints.Within Cenozoic, five major tecto-sedimentary cycles are identified:2 Paleocene cycles: A Danian-Selandian cycle (P1), and a Thanetian cycle (P2), both characterized bycarbonate plat-form growth and limited compressive deformations.3 Eocene cycles: An Ypresian-Lower Lutetian cycle (E1) composed of prograding deltas from east towest that redistribute material coming from the emerging mountain belt in eastern Pyrenees. This progradationtrend leads to relatively quick infilling of the available space and emersion of a large part of the basin.A Lutetian-Bartonian cycle (E2) composed of mixed carbonate siliciclastic deposits.A Priabonian cycle (E3) marked by a large scale emersion of the basin and deposition of fined-grainedcontinental sedimentation (Molasses d’Aquitaine).The timing of deformation is refined and confirms (1) the onset of compressive deformations duringupper Cretaceous, (2) the occurrence of a relatively quiet period during Paleocene (Danian-Lower Thanetian),and (3) a major period of basin deformation during Eocene. Within the basin, compressive deformations takeplace at both basin and local scale, the latter being mainly recorded as reactivation of inherited extensivefaulting dating from Albian and /or late Variscan extension.Within Eocene, two periods of deformation corresponding with the two successive tecto-sedimentarycycles (E1 and E2) are identified. Onset of compressive deformations is diachronous from east to west.Early Eocene deformations mainly take place in the eastern and central part of the basin, with reneweddeformations around Paleocene-Eocene boundary, coeval with the onset of terrigenous input from the growingmountain belt, and major pulse by Upper Ypresian. Late Lutetian-Early Bartonian deformations during cycleE2 are recorded throughout the basin and trigger major depocenter shifts.Together with the well known timing of the southern Pyrenean foreland deformations these data yieldsnumerous constraints about the Pyrenean orogenic prism evolution.Acknowledgments: These results were acquired during the Gaia project founded by TIGF, BRGM andAgence de l’Eau Adour/Garonne which aims to constrain the nature and dynamics of deep Upper cretaceousand Tertiary aquifers of the Aquitaine basin