Anatomy of a ‘fossil’ landslide from the Pleistocene of SE Spain

Pleistocene landslide failures are rarely recorded in the literature due to difficulties in recognition in the field. An adaptation of standard landslide classification based on activity is used to identify and examine the significance of a ‘fossil’ Pleistocene landslide from the Mocatán catchment of the Sorbas Basin, SE Spain. Recognition of the landslide is based on identifying key, but subtle anomalies in the geology and drainage. The fossil landslide at Mocatán developed principally in response to a rapid increase in valley incision rates associated with capture-induced base-level changes in the master drainage. This was facilitated by the weak sand and silt lithology of the study area. The landslide was a significant morphological modifier of the environment. Holocene drainage follows the original landslide morphology, whilst more recent gullying and piping exploits planes of weakness developed within the internal body of the landslide feature. In addition, the landslide removed much of the Pleistocene divide, facilitating future river capture.