Erosion history from incision modeling and river profile morphologies: example from the Tekeze River System, Ethiopian Plateau, East Africa

The Ethiopian Plateau in East Africa is arguably one of the best natural laboratories to study erosion from river morphology as the plateau has deeply incised by two major river systems of the Nile, the Blue Nile River in the south, and the Tekeze River in the north, yet an understanding of the incision history in the Tekeze River System remains undocumented. This research utilizes 3D incision model and bedrock river longitudinal-profile morphologies to investigate incision rate, magnitude, and timing. Incision data, generated from geochronologic age of lava flow integrated with SRTM-derived digital elevation models (DEMs), and river morphologic data, extracted from tributary long profiles, suggest that the plateau is experiencing differential incision since similar to 30 Ma, with an increased rate at similar to 10 Ma. Incision map reveals that majority of the incision occurred along the tributaries of the Tekeze River, with the deepest incision of 1.6 km observed in the tributary Zerima. Longitudinal profiles of 23 tributaries show records of at least two major tectonic knickpoints, indicating at least three incision phases (phase I-III) where long-term incision rate since similar to 30 Ma is similar to 40 m/m.y. that started to increase to similar to 100 m/m.y. since similar to 10 Ma. Normalized steepness index (k (sn) ) from long profiles indicate higher incision within the plateau interior and along the rift-flank, but lower incision around Precambrian shear zones. Landscape evolution of the Ethiopian Plateau presented here contributes toward understanding of the geodynamics of the world's largest active continental rift system.