More than 5000 years of interaction between aeolian, fluvial and anthropogenic systems in the central Egyptian Nile valley

Interactions between aeolian processes and the Nile fluvial system have been illustrated for the late Pleistocene at many sites along the River Nile, but for the Holocene period almost no data is available on this interaction. In this study we reconstruct the interaction between the South-Rayan Dune Field (SRDF) and the Nile valley in central Egypt for the last 5000 years by applying a field-based geomorphic approach, combining geophysics, sediment coring, quarry stratigraphy, geochemistry and radiocarbon dating. Three main units/periods could be distinguished: the Pleistocene Nile braidplain, the aggrading Holocene Nile silts, and the Late Holocene desertification, with dune expansion from the Western Desert into the Nile floodplain. The latter is indicated by an intercalation of flood deposits and dune sediments, with increasing thickness of Nile silt layers at greater depths. The transition from the second to the third unit most probably corresponds to the drying period characteristic for the Nile River Basin and the Sahara since the Mid-Holocene. Several cultivation layers, the oldest dating from the onset of the Old Kingdom, could be detected illustrating the presence of humans in a fluvial landscape that becomes influenced by aeolian processes. Through time the Nile floods were more and more blocked by invading dunes, although the sand flux into the Nile valley was insufficient to block the Nile itself. It is, however, suggested that invading sand dunes shifted the Bahr-Youssef channel further east. At present, the major process shaping the interaction area is of anthropogenic origin. Field observations and satellite images from 1963, 1984 and 2003 showed that dunes are being removed at high rates by quarrying activities, leveling, irrigation and the establishment of agriculture. As such, these sediment archives providing valuable information on the Holocene fluvial-aeolian interactions are being obliterated.status: publishe