(ESH) Collaborative Research: Lake Quaternary Climatic and Glacial History of Africa from Cosmogenic Dating of Glacial and Lake Deposits

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9632277 Zreda Reconstruction of the timing and extent of past glaciers and closed-basin lakes is critical for understanding regional and global climatic changes during the Quaternary. Such data are critically needed in the tropics, and equatorial Africa in particular, because of considerable discrepancy between paleoclimates deduced from terrestrial records and those calculated using general circulation models. Development of high quality terrestrial paleoclimatic data bases is one of the primary research needs in paleoclimatology. The proposed research contributes to fulfilling these needs by providing accurately dated, quantitative climatic proxy data for climatically sensitive locations in the equatorial and subequatorial Africa. Glacial deposits have been recognized and mapped in alpine regions of subtropical northwestern (the High Atlas) and tropical east-central Africa (Kenya and Kilimanjaro, among others). At these locations, multiple moraine systems record past glacier extent and provide an important proxy of previous climatic fluctuations. Very few of these landforms have been numerically dated because of lack of datable material associated with glacial deposits. Consequently, local chronologies have been based mainly on stratigraphic relationships between landforms and comparative relative weathering studies. We propose to use cosmogenic isotope dating methods (36Cl,10Be, 26Al,14C, 21Ne and 3He) to establish chronology of glaciations in Africa for the past 100,000 years or more. We also plan to use cosmogenic nuclides to date paleolake shorelines from accessible locations where strand lines are well preserved and have appropriate surfaces to date. High resolution glacial and lake-level chronologies from these sensitive locations should provide important data relevant to understanding the factors controlling late Quaternary climates in equatorial and subtropical regions of Africa. The final goal of the proposed project is to synthesize the geochronological inf ormation obtained from the above sources into a coherent paleoclimatic record and to place this regional reconstruction in the context of global climate change in the late Quaternary. Our geological and paleoclimatic data collected in Africa will contribute to the construction of the global database of Pleistocene glaciations based on cosmogenic dating terrestrial deposits. The results will be valuable for researchers in the areas of Quaternary geology, geomorphology, glaciology, geochemistry, paleoclimatology, atmospheric sciences and hydrology. ??