Neogene tectonics in Portugal

Abstract

The most important manifestation of the alpine tectonics in the Iberian Peninsula is the Betic Chain corresponding, in this peninsula, to the front of the Alpine chain. Thus, all the territory situated to the North-West (including Portugal) may be regarded as the foreland of this chain (RIBEIRO, 1988). Nevertheless, this foreland is also rather deformed, generally through the reactivating of deep and late hercynian fractures striking from ESE-WSW to NE-SW, as well as fractures striking sub-meridianly, linked to the opening of the Atlantic and the formation of the Lusitanian basin in the westernmost side of the Iberian Peninsula (Fig. 1). The Algarvian basin is a particular case in this general framework, for the main structures are two flexure lines striking E-W, connected to its evolution during the Mesozoic, having been reactivated during the Cenozoic. In the initial stage the alpine compression emphasizes the bending associated to the flexures that are progressively transformed in S-verging reverse faults and overthrusts. The role performed by the Quarteira fault is also important, for more than once during the Neogene it forms the frontier between two morphological and sedimentological domains (PAIS, 1982; KULLBERG et al., 1992).