Inverted topographic features, now submerged beneath the water of Lake Nasser, document a morphostratigraphic sequence of high-amplitude late-Pleistocene climate oscillation in Egyptian Nubia

Abstract

The Nile Valley between the Second Cataract at Wadi Halfa and the First Cataract at Aswan has been inundated behind two dams – the Aswan Dam, first built in 1902, and the High Dam (Sa'ad el A'ali), that blocked the flow of the Nile in 1964. The anticipated loss of archeological monuments in Lake Nasser, the reservoir behind the High Dam, initiated an international campaign to protect, move, or at least document as many of those monuments as possible.The UNESCO Campaign to Salvage the Monuments of Nubia included two projects that undertook to record the prehistoric archeology of the reservoir area; each of those projects engaged geologists to help place archeological sites in rigorous stratigraphic contexts. Thus, the Nile Valley between Wadi Halfa and Aswan was the site of an intensive investigation of late-Cenozoic geologic history.In this paper we summarize the principal stratigraphic elements of the suite of sediments and landforms that characterize the late-Cenozoic geology of Egyptian Nubia. Those elements include:1.Early Nile Gravel (ENG), a Nile flood-plain gravel deposited while humans were manufacturing Acheulean artifacts in the Nile Valley.2.Wadi Conglomerate (WCGL), a wadi-floor gravel topographically inverted to form sinuous ridges in the time after deposition of ENG.Because of the deep incision of the Nile Valley and immediately adjacent tributary wadis, the terrain close to the Nile, within the Reservoir area, preserves multiple generations of wadi inversion, a complex morphostratigraphic sequence not described from other areas in Egypt. The oldest body of WCGL was deposited at the same time as the ENG was accumulating.3.Late Nile Sediments (LNS), a section of younger (∼27,000-5000 14C yrs BP) sediment representing both local components and Nile-deposited components, that enclose a rich inventory of prehistoric cultures younger than Acheulean.Although examples of WCGL can be studied at locations remote from the Aswan Reservoir, most outcrops of ENG, WCGL, and LNS described in the field in Egyptian Nubia are now submerged under the water of the Reservoir.