A crustal-scale section of the NW Iberia: deformation mechanisms and transfer during the Alpine compression

SEISMIX 2024, Abstract volume - 18 - A crustal-scale section of the NW Iberia: deformation mechanisms and transfer during the Alpine compression I. DeFelipea, P. Ayarzaa, I. Palomerasa, M. Ruizb, J. Andrésc, and R. Carbonellb aDepartamento de Geología, Facultad de Ciencias, Universidad de Salamanca (Spain), ide[email protected]s, [email protected]s, [email protected], bGeosciences Barcelona, GEO3BCN-CSIC, Barcelona (Spain), [email protected], [email protected], cInstitut Cartogràfic i Geològic de Catalunya, Barcelona (Spain), Juvenal.Andre[email protected] Orogen formation, tectonic inversion and deformation transfer are processes that shape plate boundaries, However, the crustal deformation mechanisms that govern these processes vary deeply depending on the Peninsula comprises from north to south: i) the partially inverted passive continental North Iberian Margin (NIB), ii) the Cantabrian Mountains (CM) formed in the northern boundary of the Iberian subplate during the Alpine compression, and iii) an intraplate range, the Spanish-Portuguese Central System (SPCS). In addition, the CM and SPCS are separated by the Duero Cenozoic basin which represents an elevated plateau (~800 m), whereas to the south of the SPCS, the Madrid Cenozoic basin is located at 400 m altitude. Here, we present a 650-km long crustal-scale cross-section going from the NIB to the south of the Madrid Cenozoic basin. The latter is based on new hyperbolic moveout processing of wide-angle seismic reflection/refraction data and on the reinterpretation of previous Pwave velocity models. Our data show an asymmetry of the Moho reflections at both sides of the SPCS and deep subvertical reflectors to the south of the SPCS that we interpret as the image of south-vergent crustal-scale thick-skinned thrusts. This contrasts with the deformation pattern of the CM, where deformation is decoupled between the upper and lower crust and only the Iberian lower crust subducts to the north reaching at least 45 km. This crustal architecture results from the inversion during the Alpine contraction of inherited structures and weakness zones: mid-Cretaceous extensional detachments in the NIB and CM, and lateto post-Variscan granitoid intrusion that prompted crustal-scale fault nucleation in the contact with the host rocks in the SPCS. Here, the Conrad discontinuity separating the upper and lower crust was assimilated during granitoid intrusion in the late-Variscan extension, constraining the pattern used to accommodate deformation and playing a key role in the final contrasting altitudes of the Acknowledgements This study was supported by: The Spanish National Research Program under grants (CGL2014-56548P; CGL2016-81964-REDE), the Generalitat de Catalunya (2017-SGR-1022) and the Junta de Castilla y León (SA084P20).