HR: 0800h
AN: U21A-0702    [Abstracts]
TI: Extensional Tectonics and Paleoclimate of the Albertine and Edward Rifts: Constraints from Integrated Seismic Reflection and Topographic Studies
AU: * Karp, T
EM: tkarp@syr.edu
AF: Department of Earth Ciences Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244 United States
AU: McGlue, M M
EM: mmmcglue@syr.edu
AF: Department of Earth Ciences Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244 United States
AU: Scholz, C A
EM: cascholz@syr.edu
AF: Department of Earth Ciences Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244 United States
AU: Kasande, R
AF: Petroleum Exploration and Production Department, PO Box 9, Entebbe, 99999 Uganda
AU: Mugisha, F
AF: Petroleum Exploration and Production Department, PO Box 9, Entebbe, 99999 Uganda
AB: Lakes Albert and Edward are among the largest lakes in Africa and form substantial reservoirs for tropical precipitation within the Upper Nile Watershed (UNW), the equatorial headwaters supporting annual discharge of the main Nile River into the Mediterranean Sea. Extensional processes forming Lakes Albert and Edward have driven landscape evolution, manifested in significant topography and reversed drainages networks. Consequently, the UNW, including Lakes Albert, Edward, Victoria, and Kyoga, and their riverine connections, provide an important case study for drainage basin evolution in actively extending continental lithosphere. In addition to multiple scales of tectonic deformation, high frequency climate change affects the basins in the UNW, which record moisture signals from both the Indian and Atlantic Oceans. Paleoclimate proxy data indicate the desiccation of Lake Victoria and cessation of Victoria Nile flow during the Last Glacial Maximum (22 - 18 ka). However, the response of Lakes Albert and Edward during this time period is not fully resolved. In 2003, 1600 line km of multichannel seismic reflection and high resolution echo-sounder data were collected from Lake Albert, while 200 km of 1 kHz seismic reflection data were collected from Lake Edward. In conjunction with recently released digital elevation models, we investigate both tectonic and climatic processes operative in the basins. In Lake Albert, we are able to map depth to pre-rift basement, basin boundary fault as well as intrabasinal fault geometries that control both bathymetry and sediment distribution. Shallow reflections suggest desiccation of the lake, probably during the LGM; these results tie well with published sediment core data. Acoustic data from Lake Edward record two regression events, although this lake apparently escaped LGM desiccation, and may contain a complete, high-resolution archive of Quaternary climate change in its deep-water sequences. Our interpretations provide another incremental step toward a more complete understanding of Lakes Albert and Edward. These acoustic data represent a new opportunity to resolve important questions regarding the long term (ca. 10 Ma) tectono-climatic evolution of region, which can be used as a baseline for constraining environmental conditions during hominid evolution in East Africa.
DE: 8109 Continental tectonics--extensional (0905)
DE: 3025 Marine seismics (0935)
DE: 1815 Erosion and sedimentation
DE: 1836 Hydrologic budget (1655)
SC: Union [U]
MN: 2004 AGU Fall Meeting