Evolução Quaternária do Graben da Vilariça (Trás-os-Montes, NE Portugal)

Abstract

In Portugal, the Douro River has a first large bend, leaving it's E-W general orientation after the Spanish border and near the Coa River mouth; another infiection occurs in Pocinho, where the Douro River fills the Vilari\a tectonic depression and receives the water from the Sabor River and the Vilari\a stream. The Vilari\a stream fills a NNE-SSW fiat valley situated between Serra de Bornes and the Sabor River. Quaternary evolution of this sector of the Hesperic Massif is recognized by the valley morphology and sediments, the Serra de Bornes' uplift and tectonic displacement (horizontal and vertical) ofgranites and Paleozoic series. All these evidences are associated with the Bragan\a-Vilari\a-Manteigas NNE-SSW tectonic accident, where more sediments are being studied. Many of these sediments have in common an alluvial fan origin and ages since Paleogene are proposed. Vilari\adepositsand Pleistocene Douro terraces present identical characteristics in geomorphological position and sorne sedimentologic features like reddish color and kaolinite-illite-smectite clay association; these similar characteristics justify a Quaternary age proposal for the Vilari\adeposits. The variation ofother sedimentological characteristics along the valley suggests the presence of several alluvial fans.