Cenozoic landscape development within the Central Iberian Chain, Spain

In the Central Iberian Chain (Spain), covering an area of some 7400 km2, up to seven stepped erosion surfaces are determined from aerial photographs and field observations. These planation surfaces situated between 1000 and 1600 m a.s.l. are separated by erosional scarp slopes. Most parts of the erosion surfaces are developed on Mesozoic limestones and form stepped rims around the main elevations of the Iberian Chain. It is proposed that the surfaces were formed by erosional events associated with periods of uplift related to Eocene–Miocene compressional tectonic activity. The palaeogene uplift was related with syntectonic sedimentation in internal basins with up to 3500 m of accumulated thickness. During the Neogene (Middle Miocene–Pliocene) post-tectonic period, the lowered synclinal areas formed residual, internally drained basins that were filled with non-marine deposits (mainly clays and limestones). The filling of the internally drained sedimentary basins located within the Iberian Chain onlapped onto the ancient erosional surfaces, covering the lower younger levels. The recent landscape evolution of the whole area is controlled by the capture of the internal basins and the dissection of the ancient relief by the present-day fluvial network. This process is related with the transition from internal to external drainage of the Ebro basin.