Análise dos perfis longitudinais de tributários do rio Douro português, sua contribuição para identificar o ancestral rio Douro, prévio à etapa de encaixe da rede hidrográfica

Abstract

Projection of the concave graded long profile of the uppermost reaches of tributary streams of the Douro River (Portuguese sector) has been used to evaluate patterns of fluvial incision and their relationship to differential uplift across tectonic blocks. The graded profile represents an ancestral form of the Douro River that is different and has evolved to the modern entrenched convex form. Within the most upstream reach located Arribas do Douro reach (along the Portuguese-Spanish border) incision values are >500m, contrasting with 440 m near the Vilariça fault, and >600 m within in the downstream Plateau and Mountain region of NW Portugal. The graded profile reaches reflect an established connection to the Atlantic coast by the ancestral Douro River; whilst the later incision stage relates to continuous crustal uplift, lower sea-levels and cooler climates, with localized differential uplift along NNE-SSW left lateral strike-slip faults.