The MARCONI-3 Deep Seismic Reflection profile: structure of the North Pyrenean foreland at the eastern part of the Bay of Biscay

The MARCONI-3 profile denotes that the structure of the North Pyrenean foreland at the western part of the Parentis Basin consists of a wedge of uppermost Cretaceous to Cenozoic synorogenic sediments lying on the top of a thinned continental crust with a major Mesozoic Basin to the north, the Parentis Basin, and a coeval structural high to the south, the Landes High. The Parentis Basin appears bounded southwards by a major normal fault. It is filled by a thick carbonate succession affected by a salt ridge and diapirs formed during the Albian-Late Cretaceous and squeezed during the late Eocene-middle Miocene. The Landes High includes a thin pre-Upper Cretaceous cover which, together with the synorogenic sediments, is deformed by a thrust wedge that constitutes the north-Pyrenean front. This overall structure evidences that the Mesozoic extension played an important role both in the location and features of the north-Pyrenean contractional deformation. Specially, the Alpine structure in the Parentis Basin denotes that the Landes High acted as a buffer for the north propagation of the Pyrenean deformation until early Miocene and vanished afterwards during the last stages of Pyrenean development when some basement faults reactivated in the Parentis Basin.