Constraints Imposed by Rift Inheritance on the Compressional Reactivation of a Hyperextended Margin: Mapping Rift Domains in the North Iberian Margin and in the Cantabrian Mountains

Abstract

The Alpine Pyrenean‐Cantabrian orogen developed along the plate boundary between Iberia and Europe, involving the inversion of Mesozoic hyperextended basins along the southern Biscay margin. Thus, this margin represents a natural laboratory to analyze the control of structural rift inheritance on the compressional reactivation of a continental margin. With the aim to identify former rift domains and investigate their role during the subsequent compression, we performed a structural analysis of the central and western North Iberian margin, based on the interpretation of seismic reflection profiles and local constraints from drill‐hole data. Seismic interpretations and published seismic velocity models enabled the development of crustal thickness maps that helped to constrain further the offshore and onshore segmentation. Based on all these constraints, we present a rift domain map across the central and western North Iberian margin, as far as the adjacent western Cantabrian Mountains. Furthermore, we provide a first‐order description of the margin segmentation resulting from its polyphase tectonic evolution. The most striking result is the presence of a hyperthinned domain (e.g., Asturian Basin) along the central continental platform that is bounded to the north by the Le Danois High, interpreted as a rift‐related continental block separating two distinctive hyperextended domains. From the analysis of the rift domain map and the distribution of reactivation structures, we conclude that the landward limit of the necking domain and the hyperextended domains, respectively, guide and localize the compressional overprint. The Le Danois block acted as a local buttress, conditioning the inversion of the Asturian Basin.

Ambient noise tomography of the southern sector of the Cantabrian Mountains, NW Spain

“…The thickening occurs preferentially in the crust that had previously been extended during the two rifting episodes (Fernández-Lozano et al 2012). In fact, there is a sharp gradient in thickness that coincides partly with the trace at the surface of the Ventaniella fault (Cadenas et al 2018). The Ventaniella fault is a rectilinear crustal fault 320 km long on land and extending for more than another 150 km beneath the sea within the Bay of Biscay continental platform, where it is named as the Cantabrian fault (Fernández-Viejo et al 2014; Fig.…”

“…Between late Jurassic and early Cretaceous, a major extensional episode produced the opening of the Bay of Biscay and the current crustal structure mostly to the east of the study area, for example, the Basque-Cantabrian basin. Details on the effects on the continental margin and the nature of the extension can be found in Cadenas et al (2018).…”

“…Although the fault is exposed at the surface, it is difficult to extract information at depth about its inclination and offset, given that the latter is difficult to resolve with current geophysics. Cadenas et al (2018) have suggested the idea that the fault can be rooted in the lower crust. This is a working hypothesis for a number of recent studies focusing in the understanding of the structure of the fault throughout the crust.…”

Shaping of intraplate mountain patterns: The Cantabrian orocline legacy in Alpine Iberia

“…These differences are highlighted by strong changes in the depth to the Moho, from 28-30 km offshore to 34-41 km beneath the main mountain uplifts (Montes de León, Spanish Central System, and Cantabrian Mountains, respectively; Pedreira et al, 2007;Díaz and Gallart, 2009;Díaz et al, 2015;Torne et al, 2015). Deformation started in the late Eocene and was well recorded in the Cantabrian continental shelf (Pedreira et al, 2015;Cadenas et al, 2018, and references therein). The cause of this shortening was the underplating of part of the Bay of Biscay crust under Iberian crust, as revealed by seismic data (Alvarez-Marrón et al, 1996, 1997Gallart et al, 1995;Fernández-Viejo et al, 1998Ayarza et al, 2004;Gallastegui, 2000;Gallastegui et al, 2002;Pedreira et al, 2003Pedreira et al, , 2007Pulgar et al, 1996).…”

Reply to Comment by Pedreira et al. on “Reconstruction of the Exhumed Mantle Across the North Iberian Margin by Crustal‐Scale 3‐D Gravity Inversion and Geological Cross Section”

“…Since there is no major frontal thrust over the Duero Basin (Alonso et al, ), these authors propose that most of the displacement (~75 km) occurred along a north‐vergent accretionary wedge or tectonized zone at the toe of the continental slope of Le Danois Bank, being transferred at depth to the 60–90‐km northward subduction. However, recent interpretations of high‐resolution seismic reflection data (Cadenas et al, ; Zamora et al, ) reveal that the displacement accommodated by reverse faulting in the retrowedge south of Le Danois Bank was greatly overestimated.…”