Late Holocene environmental changes and present-day geomorphic processes in the Wurgo catchment (Wollo, Ethiopia)

The recent geomorphic evolution of a river catchment, located in Wollo (Ethiopia) between 2794 and 3374 m a.s.l., is outlined. The catchment is carved in Tertiary volcanics, intruded by felsic and mafic dikes. The slopes are bare and widely affected by erosion. At the slope toes thick colluvial deposits are found. Deep gullies cut these deposits, showing buried soils overlying alluvial gravels, likely emplaced during the last «Glacial». Most gullies have developed during the last decades, probably due to minor climatic fluctuations. A sequence of colluvial/alluvial deposits and buried soils, the lowest of which is dated 3900 yr 14C BP (2570-2145 cal. BC), suggests a progressive reduction of vegetation cover likely due to climate change to drier conditions and man-made forest clearing.