Quaternary dissection of the river Yeltes pediment zone (Salamanca)

Abstract

The Yeltes river, is a tributary of the Tormes River and native of the Peña de Francia range mountains. At the exit of the Peña de Francia System the river is framed in a fringe of alluvial sediments of triangular plant, formed by rañas and fluvial terraces, belonging these to the southern piedmont of the Ciudad Rodrigo's basin, which is built on a red miocene formation that seals a filling fundamentally arkosic, attributed to the Middle-Upper Paleogene. The upper part of this piedmont, which is prolonged toward the mountainous interior, is constituted by a system of big alluvial cones with the character of raña. These fans are constituted by fluvial sediments of high energy whose successive stepping in more and more lengthened platforms, mark the rhythm of the dissection until the current definition of the river Yeltes. The fringe of fluvial deposits associated, with their changing features (mainly edafic and of alteration), in parallell to their evolution, lengthens from the big initial fans toward the northern limit of the grave, where they are strangled by the fitting of the river. This strangulation, caused by the morphological and lithostructural conditioning exercised by the substrat in the layout of the river, defines an anomalous cartographic situation in connection with other well-known piedmonts of the Plateau. To sum up the age of the different episodes of their evolution is at the moment impossible.