Contribuição para a análise tectono-sedimentar do Fosso de Aljezur (SW de Portugal)

Abstract

Key-words: Cenozoic; Portugal; alpine tectonics; sedimentology; pull-appart basins. The Aljezur "graben" is a crucial piece in understanding lhe Caenozoic evolution of the SW atlantic portuguese edge. Detailed study ofthe sedimentary filling and bordering accidents allows the identification or several evolution sleps since the Miocene. The graben is bordered by accidents that dislocate geomorphologic surfaces (Littoral Platform to lhe W, Interior Platform to the E), and also Neogene sedimentary units. The sedimentary filling is composed by conglomerates and sands grading into clays and bioclastic limestones (Burdigalian to Serravalian), upon which lie unconfonnably fine reddish sands, sometimes with abundant micas. Genetic and geometric relationships between these sands, those in higher surfaces outside the "graben" and the main bordering faults, are discussed. As a conclusion, lhe reconstruction of the tectono-sedimentary evolution is attempted, integrating it in a ''pull-apart'' context associated with lhe Messejana-fault syslem and it´s reactivation by the differently orientated alpine compressions.