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

Abstract

Tectonic inversion of continental passive margins, orogens formation and deformation transfer to build intraplate ranges are processes that shape plate boundaries, define topography, and delineate continent/ocean transitions. However, the crustal deformation mechanisms that govern these processes vary depending on the tectonic setting and on the overlap of successive tectonic phases. The central and NW Iberian Peninsula comprises from north to south: (i) the North Iberian Margin (NIM), a partly inverted passive margin with limited oceanic subduction, (ii) the Cantabrian Mountains (CM), formed in the northern boundary of the Iberian microplate, and (iii) the Spanish-Portuguese Central System (SPCS), an intraplate mountain range. With the aim of unraveling the crustal-scale structure and the deformation mechanisms in these areas, we present a 650-km long cross-section from the NIM to the south of the Madrid Cenozoic basin based on new wide-angle seismic reflection/refraction data and on the reinterpretation of P-wave velocity (Vp) models. The hyperbolic moveout seismic data revealed an asymmetry of the PmP phases (Moho reflections) at both sides of the SPCS and deep subvertical reflectors to the south of the SPCS, that we interpreted as the image of south-vergent crustal-scale faults. In contrast, in the CM the Vp models presented show the northwards subduction of the Iberian lower crust. Therefore, the deformation mechanisms that govern the current crustal architecture in the central and NW Iberian Peninsula are a crustal-coupled deformation with significant vertical displacement in the SPCS and a crustal-decoupled deformation with mainly horizontal displacement in the CM.