WIDESPREAD DROUGHT IN TROPICAL EAST AFRICA DURING THE GRAND SOLAR MAXIMUM

New multi-proxy data from Lakes Edward, George and Kyoga, East Africa document significantly reduced lake levels between 1000 and 750 cal. years before present (BP). In the shallow lakes basins of George (central basin) and Kyoga, evidence for aridity is provided by a distinct desiccation surface of gray mottled clay with organic matter content below 20% and water content values of 60%, both well below typical values for the biogenic oozes that overlay these surfaces. Dates from these surfaces suggest that they may be linked to geochemical evidence for increased aridity around Lake Edward, which is hydrologically connected to Lake George. In Lake Edward sediments, a large positive spike in the % Mg in inorganic calcite occurs from 940 to 790 cal. years BP. The timing of all of these events, particularly the Edward record, corresponds closely with the Grand Solar Maximum and supports solar forcing of increased aridity in tropical East Africa at this time. Prior studies on smaller lake basins in the region, e.g. Lake Naivasha, have proposed a solar influence on tropical rainfall, and our new data make evident that this drought also had significant effects on the large lakes of the equatorial region. Following this period of aridity, sedimentological evidence and biogenic silica profiles from George and Kyoga indicate that both basins supported a shallow marsh prior to a return to open water conditions dominated by non-silicic algal populations.