ARSF project ET07/07: Late Pleistocene desiccation of Lake Tana, Source of the Blue Nile. Led by: Dr. Charles Bates, School of Geography and Geosciences, University of St Andrews, St Andrews, Fife, UK. Location: Blue Nile.

The Blue Nile has its source at Lake Tana in northern Ethiopia, and flows 1610km to its confluence with the White Nile at Khartoum. Although shorter than the White Nile, it contributes ~56% of total Nile discharge, rising to 68% during maximum flow, and the bulk of transported sediment. However, much less is known about the Quaternary-Tertiary geological history of the Blue Nile and its headwaters than for Lake Victoria, the source of the White Nile. A recent NERC-funded research programme on Lake Tana provided new core data (Lamb et al., 2007) that showed Tana dried out at about 17,000 cal BP, contemporaneous with desiccation of Lake Victoria. The seismic data revealed a previously unknown, thick (+100 m) sedimentary sequence with basin-wide reflecting horizons strongly suggesting numerous earlier regional, and possibly global (Heinrich?), climatic events. This was an unexpected discovery and, in order to best interpret this record, a much more comprehensive knowledge of the surrounding geology and regional tectonics was required. Due to the size of the basin (ca. 70 x 100 km) and minimal road network, airborne mapping backed by judicious ground truthing provided the only feasible solution to obtaining the required data.