Upper lithospheric transfer zones driving the non-cylindricity of the West-Pyrenean orogenic prism (Mauléon hyperextended basin)

Abstract

The Pyrenean domain records the development of a hyperextended system during the Early Cretaceous at Iberia/Eurasia plate-boundary. This rifting stage is controlled by the coeval development of N120° longitudinal and N20° transverse tectonic features. In the west-Pyrenean Mauléon basin, preserved in the heart of a N120° lithospheric pop-up, the Iholdy, Saison and Barlanès transverse structures are known to play a significant role during the Cretaceous hyperextension. Using a multidisciplinary approach combining Raman thermometry, paleostress reconstructions, seismic interpretations, 3D implicit geological modeling and passive seismic interpretation, we define these three N20° structures as syn-collisional transfer zones rooting at depth in the upper lithospheric mantle. These tectonic features significantly control the 3D structural architecture of the Mauléon basin pop-up. Indeed, the N120°-oriented thrust systems, defining the edges of the Mauléon basin pop-up, branch into these transfer zones and define corridors with differing amounts of shortening. This overall structural pattern defines drawer-like structures allowing the closure, by stages, of the former rift domain. Thus, this study clarifies the role of inherited lithospheric transfer zones in the reactivation of a hyperextended rift basin and bears upon the origin of the non-cylindrical shape of the West-Pyrenean belt.