2003 Seattle Annual Meeting (November 25, 2003)
Paper No. 90-3
Presentation Time: 8:00 AM-12:00 PM


FREIBURGER, Nick C.1, RUSSELL, James M.2, BEUNING, Kristina R.M.3, and SCHNURRENBERGER, Douglas2, (1) Geology, Univ of Wisconsin: Eau Claire, Phillips Science Hall: First Floor, Dept of Geology, Eau Claire, WI 54701, freibunc@uwec.edu, (2) Limnological Research Center, Univ of Minnesota, 220 Pillsbury Hall, 310 Pillsbury Dr SE, Minneapolis, MN 55455, (3) Biology, Univ of Wisconsin: Eau Claire, Phillips Science Hall: Room 357, Department of Biology, Eau Claire, WI 54701

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.

2003 Seattle Annual Meeting (November 25, 2003)
Session No. 90--Booth# 217
Lakes and Holocene Environmental Change: The Use of Multiproxy Lake Records for Paleoclimate Reconstructions (Posters)
Washington State Convention and Trade Center: Hall 4-F
8:00 AM-12:00 PM, Monday, November 3, 2003

Geological Society of America Abstracts with Programs, Vol. 35, No. 6, September 2003, p. 210

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