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

摘要

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 degrees longitudinal and N20 degrees transverse tectonic features. In the west-Pyrenean Mauleon basin, preserved in the heart of a N120 degrees lithospheric pop-up, the Iholdy, Saison and Barlanes 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 degrees 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 Mauleon basin pop-up. Indeed, the N120 degrees-oriented thrust systems, defining the edges of the Mauleon 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.