Geometría, estructuras y evolución de la terminación occidental de los relieves del Orógeno Alpino-Pirenaico (NO Península Ibérica)

Abstract

The geometry, structures and tectonic evolution of the western termination of the Alpine-Pyrenean Orogen relief onshore and related foreland have been studied. We present the results of structural mapping and detailed outcrop studies of Cenozoic-age structures carried out at the NW Iberian Peninsula. On the basis of this work we propose a new tectonic model for the termination. $FFRUGLQJ WR WKH LGHQWL¿HG VWUXFWXUHV WKUHH PDLQ UHJLRQV FRXOG EH UHFRJQLVHG WKH $VWXU*DODLFD $* UHJLRQ RU WKH ZHVWHUQ part of the Cantabrian Mountains (CM), characterised by thrusts with a south vergence, which are the continuation of the structures of the Pyrenees, (2) The Galaico-Leoneses Mountains (GLM), characterized by thrusts with a north vergence, and (3) The Rías Baixas-Terra Chá region (RBT) characterized by strike-slip faults with no relevant associated relief but with recent seismic activity, which represents the less deformed Alpine foreland. The western termination of the Alpine-Pyrenean Orogen is formed due to the superposition of two mountain ranges (CM and GLM) and a complex tectonic evolution. The CM were emplaced southwards and VXEVHTXHQWO\ WKH */0 ZDV HPSODFHG QRUWKZDUGV 7KH ZHVWHUQ OLPLW RI WKH (: WKUXVWV RI WKH &0 DQG WKH DVVRFLDWHG UHOLHI GH¿QH a N-S-oriented arch-shape structures (Ibias-Ancares and Rúa-Vilalba). Tectonic activity commenced during the Eocene, and in the westernmost areas during the Late Oligocene. The CM south-verging thrust activity ended at the beginning of Late Miocene, although deformation continued in the GLM with north-verging thrusts. The evidence of intense tectonic activity during the Miocene, the western migration and southward transference of tectonic activity and the interaction of two successive deformation fronts, suggests that a re-examination of the tectonic evolution of the northern Iberian microplate during the Alpine Orogeny is necessary.

Seismicity and potencially active faults in the Northwest and Central-West Iberian Peninsula

“…These types of movements are also found to the east, in the Ventaniella fault (Cantabrian Mountains) and within the Iberian Chain (e.g. De Vicente and Martín-González and Heredia, 2011b). The compression responsible for these structures is the N-S maximum horizontal stress related with the Pyrenean collision.…”

“…Bragança-Vilariça and Verín-Vila Real corridors), this took place mainly during the Late Miocene and therefore related with the Betic collision (Martín-González et al, 2011). In contrast, the Rias Baixas-Terra Cha Region (RBT) represents the less deformed region of the foreland (Martín-González and Heredia, 2011b) (Fig. 1).…”

“…The Pyrenees forms the border between Eurasia and the Iberian Peninsula microplate, trending ESE-WNW, and represents a doubly verging continental collision orogen (Choukroune et al, 1990;Muñoz, 1992;Teixell, 1998). The Alpine structures of the Cantabrian Mountains can be divided, based on involved lithologies, age and deformational style, into two regions: the VascoCantabrica (VC) in the E and the Astur-Galaica (AG) in the W (Martín-González and Heredia, 2011b) In the Astur-Galaica region, the overall Alpine structure is a regional monoclinal flexure that corresponds to the back-limb of a major fault-bend fold related to the Cantabrian Basal Thrust (CBT). This north-dipping basement thrust overturns the Mesozoic-Cenozoic sediments in the south border of the Cantabrian Mountains (Alonso et al, 1996).…”

Crustal structure of the south-western termination of the Alpine Pyrenean–Cantabrian Orogen (NW Iberian Peninsula)

“…1). In spite of the complete lack of Mesozoic rocks, the scarcity of Cenozoic sedimentary record, and the intense basement deformation, Alpine tectonic events has been unravel in the recent years from stratigraphical (Martín-Serrano et al, 1996;Martín-González and Heredia, 2011a), palaeontological (Freudenthal et al, 2010, MartinGonzález et al, 2014 and structural studies (Santanach, 1994;Heredia et al, 2004;Vegas, 2009 andMartin Gonzalez andHeredia, 2011b).…”

Palaeontological age and correlations of the Tertiary deposits of the NW Iberian Peninsula: the tectonic evolution of a broken foreland basin

“…The age of the Tertiary deposits in the NW Iberian Peninsula has not been established with certainty to date, and therefore the understanding of the tectonic evolution of the region remains imprecise and controversial (Martin-Serrano et al, 1996;Alonso and Pulgar, 2004;Barnolas and Pujalte, 2004;De Vicente and Vegas, 2009;Martín-González and Heredia, 2011b). The difficulty in dating these deposits is due to their limited exposure and the fact that they were deposited as terrigenous continental sediments, in oxidized arid or semiarid environments.…”