Earth science: Ancient river lost in the sands of time

The sandy wastes of the Western Sahara once accommodated a vast river network, according to a study published in Nature Communications this week. The findings have important implications for our understanding of the African continent under past and future climates.

Today, no major river systems exist in the Western Sahara, only a constantly shifting sea of sands. However, recent findings have suggested that this has not always been the case. The discovery of fine-grained, river-borne material in the deep ocean, and an extensive submarine channel carved into the continental shelf off the Western Sahara coast, indicate the past existence of a major West African river system. However, direct evidence of such a vast fluvial network on land has been lacking.

Charlotte Skonieczny and colleagues use orbital radar satellite imagery, which has the capability to penetrate metres of material, such as sand dunes, and map the geological features that lie hidden beneath. Using this technique, the team reveal the existence of a vast ancient river network approximately 520 km in length, which aligns almost perfectly with the submarine canyon previously identified on the adjacent coastline.

The findings have important implications for the way in which sediment records off West Africa are interpreted and for our understanding of an ancient, wetter, and possibly greener, Sahara.

doi: 10.1038/ncomms9751

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