Source-to-sink system evolution of the Nile since 70 Ma

Nile River, the longest river in the world (>6,500 km), has been studied since long time ago tracing back to the fifth century yet the timing of origin of its present-day drainage is still disputed. There are two end-members of notions of the birth of the Nile, the first one believes that the present-day Nile has been connected to the Ethiopian Plateau since ~30 Ma, while the other supports the idea of young Nile around ~6 Ma. The Nile crosses today two former endorheic systems (Sudanese and Albertine “Basins”) and one exorheic system (Tethys Margin) before finally depositing sediments in the Mediterranean Sea. Our objective here focuses on deciphering the source-to-sink scenario of the Nile through relief growth, tectonic, and climate since the uppermost Cretaceous.

The timing of the uplifts and deformation wavelengths are constrained by characterizing and mapping several generations of stepped pediments on DEM and satellite images which then dated using their geometrical relationships with dated magmatic rocks. Additionally, stratigraphic records of the sedimentary basins were studied to complement the dating of the pediments. The authenticity of the approaches is to integrate those data enclosing all the source-to-sink (S2S) systems to construct a coherent scenario of the Nile paleorouting systems especially on the dynamics of its sediment sources.

We proposed the following model for the S2S of the Nile where its catchment grew larger southwards through time. First, a significant deformation occurred around the Cretaceous-Paleogene boundary (66 Ma) with the uplift of western limit of the Nile catchment, the Darfur-Ennedi-Tibesti domains, followed by the formation of a main large pediment. Second, this pediment was then flooded during late Paleocene (58-57 Ma) until a subtle high bounding northward the endorheic Sudanese “Basin”. Consequently, carbonate platforms were widely deposited from Paleocene until middle Eocene in the Egypt extending southwards to the former Hudi Lakes in northeast Sudan and there was no siliciclastic supply for the Nile during that time. Third, the first evidence of a fluvial system (“Pre-Eonile” according to Said, 1981) was discovered during late Eocene (~37 Ma) by large channel incisions on top of the carbonate platforms. Contemporaneously, the Uweinat Dome was uplifted and likely acted as the main siliciclastic source during late Eocene to Oligocene. Fourth, the initiation of Red Sea rifts during the Oligocene followed by a major uplift at the scale of north-east Africa (~10 Ma) provoked another plausible siliciclastic source, the Red Sea Hill’s flanks, in addition to the Uweinat Dome. Fifth, during the capture of the Sudanese endorheic system in the Early Pliocene (~4 Ma), the Nile catchment grew significantly larger and the sources were actively provided by the Darfur and Ethiopian Plateau. Finally, during middle-late Pleistocene (< 1 Ma) the Nile completed its present-day catchment by capturing the Albertine endorheic system and the siliciclastic sediments were supplied by the Ethiopian Plateau and the East African Dome.