The role of the Bay of Biscay Mesozoic extensional structure in the configuration of the Pyrenean orogen: Constraints from the MARCONI deep seismic reflection survey

Abstract

Seismic interpretation of the MARCONI deep seismic survey enables recognition of the upper crustal structure of the eastern part of the Bay of Biscay and the main features of its Alpine geodynamic evolution. The new data denotes that two domains with different Pyrenean and north foreland structures exist in the Bay of Biscay. In the eastern or Basque‐Parentis Domain, the North Pyrenean front is located close to the Spanish coast, and the northern foreland of the Pyrenees is constituted by a continental crust thinned by a north dipping fault that induced the formation of the Early Cretaceous Parentis Basin. In the western or Cantabrian Domain, the North Pyrenean front is shifted to the north and deforms a narrower and deeper foreland basin which lies on the top of a transitional crust formed from the exhumation of lithospheric mantle along a south dipping extensional low‐angle fault during the Early Cretaceous. The transition between these two domains corresponds to a soft transfer zone linking the shifted North Pyrenean fronts and a north‐ to WNW‐directed thrust that places the continental crust of the Landes Plateau over the transitional crust of the Bay of Biscay abyssal plain. Comparison between this structure and regional data enables characterization of the extensional rift system developed between Iberia and Eurasia during the Late Jurassic and Cretaceous and recognizes that this rift system controlled not only the location and features of the Pyrenean thrust sheets but also the overall structure of this orogen.

Plate kinematics in the Cantabrian domain of the Pyrenean orogen

“…The excess length in the crust was asymmetrically accommodated by the reactivation of the inherited extensional detachment (e.g. Gallastegui et al, 2002;Roca et al, 2011;Fernández-Viejo et al, 2012), above which the first embryonic contractional structures of the retro-wedge developed. It is worth remarking that, in a map view, the northward concave shape of all the structural features of the Cantabrian domain (Fig.…”

“…1a) (e.g. Roca et al, 2011); (4) a Mesozoic NNE-SSW oriented stretching direction is also observed in the Organyà Basin, which is located in the Pyrenean Mountain Range and belongs to the western portion of the Bay of Biscay-Pyrenean rift system. In agreement with these observations, all of them showing an almost ridge-perpendicular (i.e.…”

“…To the east, the Pyrenean arm of the Mesozoic Bay of Biscay-Pyrenean rift system has been sandwiched between the subducting Iberian Plate and the overriding Eurasian one (e.g. Choukroune et al, 1989;Muñoz, 1992;Teixell, 1998;Pedreira et al, 2007;Roca et al, 2011), which resulted in the development of a doubly vergent orogen. In the western portion of the Pyrenean orogen, hereinafter named Cantabrian domain, convergence involved the deformation of the southern passive margin of the Mesozoic rift system (Fig.…”

Characterization of a complex near-surface structure using well logging and passive seismic measurements

“…The North Castilian Platform was formed during the Mesozoic extensional phase (Roca et al, 2011). During this period, the basin was filled in by a thick sedimentary sequence (Quesada et al, 2005).…”

El sistema turbidítico conglomerático de Andatza (Pirineos occidentales): Estratigrafía, sedimentología y control estructural

“…Basin development was intimately linked to the relative motion of the Iberian and Eurasian plates during the Cretaceous, which was governed by the opening of the North Atlantic Ocean and in turn resulted in the opening of the Bay of Biscay under extensional to transtensional tectonics (e.g. Choukroune & Mattauer, 1978;Montadert et al, 1979;García-Mondéjar et al, 1996;Roca et al, 2011).…”