ANALYSIS OF STREAM LONGITUDINAL PROFILES OF THE BLUE NILE DRAINAGE NETWORK TO UNDERSTAND MANTLE-DRIVEN UPLIFT OF THE ETHIOPIAN PLATEAU

We extensively analyzed stream profiles of the Blue Nile drainage network of the Ethiopian Plateau extracted from SRTM derived DEMs using stream power law. As the Ethiopian plateau has experienced 1.6 km deep incision, this study is topical to better understand landscape evolution from regional-scale to far larger continental-scale and their concomitant morpho-tectonic features in an active geodynamic context. In this study we investigate the tectonic history of the plateau by analyzing channel morphology such as longitudinal profile forms, which are also sensitive proxies for inferring incision and uplift history.

We focused on two parameters of channel long-profiles: major knickpoints and normalized steepness index (k_sn). Our study indicates that major knickpoints (relief >200 m) are distributed within highly incised areas of the plateau, setting the boundaries between high and low uplift zones of the plateau. Detailed investigation of knickpoints resulted in identifying significant proportion of them not related to any geological structures and lithology that is consistent to our previous assumption that these knickpoints are likely associated with tectonic uplift. We also found that normalized steepness index values vary systematically in upstream and downstream of the channels, indicating that tributaries are responding to differential tectonic uplifts of the region. We plan to correlate the distribution of steepness index of major tributaries with the mantle tomography of the Ethiopian plateau to accommodate more plausible causes of plateau uplift.