The Spanish Central System is a Cenozoic pop-up with an E W to NE SW orientation that affects an the crust (thick-skinned tectonics). It shows antifonn geometry in the upper crust with thickening in the lower crust. Together -with the Iberian Chain it constitutes the most prominent mmmtainous structure of the Pyrenean foreland.The evolutionary patterns concerning the paleotopography of the interior of the Peninsula can be established by an analysis of the fo11owing data: gravimetric, topographical, macro and micro tectonic, sedimentological (infilling of the sedimentary basins of the relative foreland), P T t path from apatite fission tracks, paleoseismic and instrumental seismicity.Deformation is dearly asymmetric in the Central System as evidenced by the existence of an unique, large (crustal-scale) thrust at its southern border, while in the northern one there is a normal sequence of north verging thrusts, towards the Duero Basin, whose activity ended during the Lower Miocene. This deformation was accomplished lUlder triaxial compression, Oligocene Lower Miocene in age, marked by NW SE to NNW SSE shortening. Loca11y orientations of paleostresses deviate from that of the regional tensor, follo-wing a period of relative tectonic quiescence. During the Upper Miocene Pliocene, a reactivation of constrictive stress occurred and some structures underwent rejuvenation as a consequence of the action of tectonic stresses similar to those of today (lUliaxial extension to strike slip -with NW SE shortening direction). However, the westernmost areas show continuous activity throughout the whole of the Tertiary, with no apparent pulses. At the present time there is a moderate seismic activity in the Central System related to faults that were active during the Cenozoic, with the same kinematic characteristics.
The Iberian microcontinent and its connected oceanic crust are affected by deformations related to the Eurasian‐African plate boundary. Active stress inversions from populations of moment tensor focal mechanisms have been performed around and inside the Iberian peninsula, using a total of 213 moment tensor estimates. Main results are as follows: (1) The tensorial solutions show better consistency and lower misfits compared to those obtained previously from first P arrival focal mechanisms. (2) Along the Eurasia‐Africa western boundary, the type of active stresses progressively changes easternward from triaxial extension to uniaxial compression along the Terceira Ridge, the Gloria Fault zone, and the Gulf of Cadiz. (3) In the Betics‐Alboran‐Rif zone, uniaxial extension predominates with Shmax N155°E trending. (4) In northern Algeria, uniaxial compression reappears. (5) The Iberian foreland is currently under strike‐slip to uniaxial extension tensorial conditions.
The Iberian Chain is a wide intraplate deformation zone formed by the tectonic inversion during the and basin evolution analysis, macrostructural Bouguer gravity anomaly analysis, detailed mapping and paleostress inversions have been used to prove the important role of strike slip deformation. In addition, we demonstrate that two main folding trends almost perpendicular (NE SW ID E W artd NW SE) were simultaneously active in a wide transpressive zone. The two fold trends were generated by different mechanical behaviour, induding buckling and bending under constrictive strain conditions. We propose that strain partitioning occurred with oblique compression and transpression during the Cenozoic.
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.
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