Sedimentary record of the Paleogene deformation in the North Pyrenean retroforeland (Aquitaine Basin) and link to the Pyrenean orogeny.

International audienceThe North Pyrenean retroforeland (Aquitaine basin) display a quite different tectonic style compared to its well known southern counterpart, and is not well known due to a lack of accurate stratigraphy and geometry at the scale of the basin. Strong efforts have been made in the recent years to improve the knowledge of the Pyrenean orogeny and Aquitaine basin. Based on the integration of more than 1000 wells and 10000 km of seismic profiles we present a synthesis of the Paleogene sedimentary record of the Aquitaine Basin. Large-scale sections, thickness and facies map at the scale of 1 My, precise the timing, intensity and distribution of the deformation. Within Cenozoic, five major tecto- sedimentary cycles are identified, 2 Paleocene cycles :A Danian-Selandian cycle (P1), and a Thanetian one(P2)., And 3 Eocene cycles:- An Ypresian- Lower Lutetian cycle (E1) composed of prograding deltas.- A Lutetian- Bartonian cycle (E2) composed of mixed carbonate siliciclastic deposits.- A Priabonian cycle (E3) marked by a large scale infilling of the basin and deposition of fined- grained continental sedimentation.The timing of deformation is refined and confirms the occurrence of a relatively quiet period during Paleocene (Danian- Lower Thanetian) although with progressively increasing sedimentation rate, followed by a syn orogenic period during Eocene. The latter is separated in two steps:- Firstly the development of a large-scale flexural basin during Early Eocene. Onset of (lim- ited) thrusting and fault reactivation is registered around Paleocene- Eocene boundary in the eastern part of the basin.- Secondly a propagation of the brittle deformation in the foreland with strong inversion and thrusting in the foreland (Audignon etc.) and complete spatial reorganization of the subsidence pattern.- A Priabonian phase of homogenous moderate subsidence during Priabonian, particularly in the eastern part of the basin.This evolution is congruent with the southern foreland one and traduces common phases of evolution. The Ypresian- Lutetian period flexure is interpreted as the consequence of the loading by the growth of the orogenic prism that took place at that time and possibly started earlier during Paleogene. The Bartonian compressive deformation of the foreland correspond to the major phase of collision. These results were acquired during the Gaia project founded by TIGF, BRGM and Agence de l’Eau Adour/Garonne