Published online by Cambridge University Press: 01 May 2009
Low-lying physiographical features in the northern Sudan are associated with Lower Tertiary “lake beds”. Some undulation may have been imposed, e.g. in the Dongola bend of the Nile. There has been little vertical river erosion below the level of the lake beds in the northern Sudan, whereas in Egypt there were long successions of Tertiary sediments, uplifts, folding, and faulting. Neither late-Tertiary marine flooding nor successive regradings of the Nile in Egypt reached the Sudan. With reference to the present flood plain the summit level of some silts of Palaeolithic age rises in a striking manner from the country around Atbara (and probably a wider area) downstream into the Dongola bend, reaches a maximum (so far as known) around Wadi Haifa, and then falls again.