The Spanish‐Portuguese Central System: An Example of Intense Intraplate Deformation and Strain Partitioning

Abstract

The intraplate deformation of Iberia during the Cenozoic produced a series of ranges and deformation belts with a wide variety of structural trends. The Spanish‐Portuguese Central System is the most prominent feature crossing over the whole of central Iberia. It is a large thick‐skinned crustal pop‐up with NE‐SW to E‐W thrusts. However, the 500‐km‐long left‐lateral strike‐slip Messejana‐Plasencia fault, also NE‐SW oriented, bends these thrusts to produce NE‐SW local paleostresses close to the fault, which seems to be consistent with a common deformational arrangement. This is also supported by the similar sedimentary infilling characteristics found in the surrounding Cenozoic basins. The moment of the maximum intraplate deformation is registered at the same time in all these basins during the upper Priabonian‐lower Chattian. As there are two possible sources for the intraplate compressive stresses, the Pyrenean (N‐S shortening) orogen to the north and the Betic (NW‐SE shortening) orogen to the south, neither can simply explain both simultaneous movements (NE‐SW strike‐slip and NE‐SW thrusting). The deduced age of the main deformation indicates a Pyrenean origin. In contrast, the concept of strain partitioning between the two types of faults gives as a result an overall north trending compression. Existing data do not support crustal detachment from the Betics neither from the Pyrenees but are consistent with a crustal uplift related to lithospheric folding. The subsequent Betic‐related stress field only slightly reworked previously Pyrenean‐related structures, except for the Portuguese sector, where tectonic activity occurred mainly in the Upper Miocene.

Lithospheric image of the Central Iberian Zone (Iberian Massif) using global-phase seismic interferometry

“…The differences below the CS affect the depth as well as the geometry of the crust-mantle interface. The Moho discontinuity in Diaz et al (2016) presents a rather flat geometry, depicting a little 1 km thick root. The results from gravity inversion, while being closer to our results regarding crustal thickness, are highly influenced by the inclusion of the topography in the inversion procedure.…”

“…The granites of the western sector correspond to the Avila Batholith, which is a vast association of igneous rocks. The current knowledge of the crustal and lithospheric structure of the Central System comes mainly from geophysical studies such as seismic data (Suriñach and Vegas, 1988;Diaz et al, 2016) and inversion and forward modelling of potential-field data (Tejero et al, 1996;de Vicente et al, 2007;Torne et al, 2015). These studies have found a crustal thickness in the range of 31 to 35 km, showing a thickening underneath the Central System with respect to the surrounding basins.…”

“…In any case, the structure of the CS suggested by the present dataset is that of an asymmetric orogen. Figure 6 shows a sketch of the interpretation of the CIMDEF GloPSI profile overlapped with the Moho geometry deduced from gravity inversion (Torne et al, 2015) and a compilation of active-source and RF Moho depths (Diaz et al, 2016). Also, the geometry of the inferred imbrication, involving just the lower crust (Fig.…”

Basement‐Cover Relationships and Their Along‐Strike Changes in the Linking Zone (Iberian Range, Spain): A Combined Structural and Gravimetric Study

“…Whether these thrust flats reactivate or cut a previous extensional detachment is uncertain (no clear synextensional growth geometries can be identified in their hanging walls and this prevents the characterization of extensional fault geometries at depth; Figure 13a). They outline an imbricate thrust system soled by a décollement in the shallow basement (Figure 8a, basement-involved thin-skinned tectonics, Pfiffner, 2006) that resembles the structural style in the eastern Central System, to the west of the study area (Figure 2;De Vicente et al, 2018). Thickness variations in relation to the Sierra de Arcos thrust (named as Sierra de Arcos Fault in Figure 13a) are in agreement with its role as the northern boundary of the Oliete subbasin (Casas et al, 1997;Soria, 1997) that (i) thinned progressively toward the east (cf.…”

Tectonostratigraphy of the Mérida Massif reveals a new suture zone exposure in SW Iberia

“…occupy intra-plate positions. Both are the result of plate tectonics in the Mediterranean domain as well as of distributed strain upon Africa-Europe convergence (Dewey et al, 1989;Jolivet et al, 2008;de Vicente et al, 2018).…”