Neotectónica del sector centro-meridional de la cuenca de Madrid

Abstract

The analysis and study of geomorphological features such as: sequence and geometrical disposition of Quaternary geomorphological units; hanging valleys; captures, straight scarps; triangular facets; tilted and deformed deposits..., together with the application of geomorphic indices such as: Stream gradient index; mountain front sinuosity index and ratio of valley-floor width to valley height, all of them indicators of recent tectonic activity, constitute the basis for the realization of a neotectonic cartography. Likewise an analysis of the longitudinal profiles of the several rivers crossing across the studied area and their sinuosity, has been made. From all that, it can be deduced that during the Quaternary the neotectonic activity in the centresouthern sector of the Madrid Basin has been important, mainly during the early-middle Pleistocene transit, when the capture of the River Manzanares by a tributary of the River Jarama, is produced by the southwestward-tilting of the La Marañosa block. Most of the geomorphological features indicators of neotectonics are associated to the large gypsum scarps bounding the main rivers, and are developed troughout the whole Quaternary, including the Holocene. On the other hand the study of the longitudinal profiles of the rivers shows a marked deviation from the theoretical equilibrium profile, being all of them affected by numerous inflections which in many cases correspond to the passing of faults perpendicularly to the river floor. Likewise the sinuosity degree of the rivers is conditioned at a small scale, by the passing of faults, or tectonic activity lines, parallel or perpendicular to the valley.