Evolution of the western Namibian drainage systems since Eocene times - a multi-methodical approach

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The planned project aims to the reconstruction of drainage basin evolution over a long period of time and large areal distribution using sediments of the recent rivers and their precursors. With respect to the constantly very low erosion rates since Eocene times, exceptionally well-preserved remnants of Eocene to recent fluvial strata and a lack of precise age determinations, the western Namibian drainage system was chosen as working area. In order to obtain precise ages of the single terrace levels and to detect changes in the provenance of the sediments, this is the first study coupling the routinely used terrestrial cosmogenic nuclides (TCN) 10Be, 21Ne and 26Al from quartz and detrital zircon geochronology using U-Th-Pb and Lu-Hf isotopics complemented by single grain morphometrics. In addition to these methods, we plan a feasability study of entirely new and advanced dating techniques including cross-calibration of 26Al and 36Cl in calcite, as well as 36Cl, 41Ca, and 53Mn in magnetite. Succeeding or not, the scientific outcome of this rather chancy objective will not put the above mentioned primary objective at risk. Based on precise age determinations from routinely used TCN and uniquely high-resolution provenance analyses obtained from zircon we will be able to establish the timing of terrace forming events, and, therefore draw further conclusions like aspects of geology and palaeogeography (tectonic uplift, incision events, variability of catchment areas). The sediments will also provide data that will facilitate the reconstruction of potential changes in the sediment fluxes, source to sink dynamics, fluvial palaeoenvironment and some palaeoclimatic conditions, like water supply and discharge. Hence, this proposal is in contrast to the vast majority of all earlier studies, which are generally limited to small areas and/or short periods of time and aim either at palaeogeographic and/or geologic reconstructions or at the understanding of palaeoclimatic conditions. Finally, the cooperation of two institutions with fully-equipped state-of-the-art laboratories accompanied with advanced experience makes this project quite unique and economical.