干旱区生态环境知识资源中心

The Western Desert of Egypt is one of the most arid areas of the world. Because of the extreme scarcity of the rainfall (less than 1 mm of annual mean rainfall in some places) and because of the amount of available sediment, aeolian processes are the major morphogenetic factors. The studies of the palaeoenvironments in this area (Wendorf et Schild, 1980; Sanlaville, 1997; Brookes, 2003; Bubenzer et Riemer, 2007) show that the climate has gradually become hyperarid between 5800 BP and 4500 BP. So, the ascendancy of aeolian processes isn’t new. During the Holocene, the aeolian processes and landforms has acted as a resource (moisture of the deposits, arable lands) and as a stress (sanding and silting up, erosion) at the same time. The geomorphological and geoarchaeological survey of the Dush area, located in the South of Kharga basin has highlighted the existence of fine-grained sediment which are neither spring deposits (as described by Bousquet, 1996) nor playa deposits (as described by Embabi, 1972, 1999, 2004). The archaeological data produced since 1976 by the IFAO (Institut Francais d’Archeologie Orientale) mission and the sedimentological analyses indicates that the sediment of these deposits had been windblown and trapped by vegetation (fields of the ancient oases). The cultivation of the fields lasted from 2500 BP to 1500 BP, allowing the height of the deposits to reach several meters. The drop of the water table and the uplift of the level of the fields forced the farmers to adapt themselves, up to the abandonment of most of the sites (around 1500 BP). After 1500 BP, the deposits have been eroded by wind, involving the formation of yardangs. The current landscape of the studied hills is the result of the succession of a period characterized by the deposition of windblown sediment linked to the cultivated fields and a period of aeolian erosion linked to the end of agricultural activities.