El Paleodeslizamiento de Villar del Olmo (Madrid, Cuenca del Tajo)

Résumé

In the western slope of Arroyo de la Vega, close to Villar del Olmo village (Madrid, Tajo Basin), there is a large rotational paleolandslide whose slided mass covers an area of 55 Hm2. The subsurface geology consists of Miocene clays, silty-clays, marls, gypsum and limestones at the top formed in a lacustrine environment. The landslide has been strongly modified by erosion and it has colluvial covers. The slip surface outcrops 50 metres above the valley bottom and it is placed on high plasticity silty clays. Deformation structures generated by progressive simple shear mechanism can be seen on the slip surface. Friction striations subsequently filled with carbonate precipitates indicate horizontal N 90º E movement direction. The landslide seems to have been triggered by the big slope associated with gullying, the level difference between the Páramo and the valley bottom (over 90 metres) and the high plasticity (and low strength) of clayey levels. This landslide is a good example of landslides generated in Tajuña and subsidiary rivers valleys of this area