New insight on paleoriver development in the Nile basin of the eastern Sahara

Abstract

Since the first detection of paleochannels beneath sand sheets and sand dunes in the Sahara using Shuttle Imaging Radar (SIR-A) data, key advances in the understanding of these features have been made. The Sahara is currently the largest and driest region on Earth. However, it was drained by numerous rivers that are now dry channels beneath sand sheets and sand dunes. The present Sahara reflects past pluvial conditions, and the transitions from heavy rainfall to arid or hyperarid conditions reveal major climate shifts. Here, we propose that the evolution of the Sahara occurred in response to the stages of the location of the African Plate relative to the Earth’s equator, i.e., as a result of the northward drift of Africa in space and time. For instance, it is probable that during the late Eocene or Oligocene the Earth’s equator was located at the current-day latitudes of Chad and Sudan. This geometry would have produced pluvial conditions throughout North Africa. With increasing drift in space and time during the Miocene, Pliocene, and Pleistocene, the source points shifted. New valleys were formed and old ones were abandoned, and the length of the main stream of the Nile increased.