Document Type

Article

Publication Date

2012

Abstract

Since the first detection of paleochannels beneath sand sheets and sand dunes U the Sahara using Shutle Imaging Radar (SIR-A) data, key advances the understanding hese features have been made. The S 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 ainfall to arid ryperarid conditions reveal major climate shifts. Here,we propose that the evolution of the Sahara occurred in- response the stages ofthe location of the African Plate relative to the Earth's equator, i.e., as a result of f the northward drift of Africa in space s .c and ime. For instance, f probable that during the late Eocene Oligocene the Earth's equator was located t the current-day latitudes of Chad and Sudan. This geometry would have produced pluvial con- ditions 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 S the Nile increased.

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