Understanding transient landscape of the Ethiopian Plateau in relation to mantle dynamics

Abstract

The Ethiopian Plateau, situated on the Western Escarpment of the East African Rift System, constitutes a part of a large igneous province that has experienced extensive flood basalt volcanism around 30 Ma related to the outpouring of the Afar mantle plume. This non-orogenic plateau with long-wavelength dynamic topography has been deeply incised by the Blue Nile River and its numerous tributaries. The plateau represents an excellent natural laboratory to study the interplay between bedrock river incision and uplift. Our analysis of a total of 202 convex upward and double-concave tributary longitudinal profiles reveals 244 knickpoints, the majority of which are not associated with lithologic boundaries or faults. The normalized steepness indices (k sn ) of these profiles vary in upstream versus downstream from knickpoints indicating variable uplift within the plateau. Our investigation of integrating mantle seismic P-wave velocity anomaly with k sn and knickpoints suggests ongoing incision of the plateau surface in response to Afar plume related mantle dynamics. Tributary reaches with higher k sn generally lie above the areas with negative velocity anomaly, thus hotter (than normal) mantle that are likely undergoing more uplift.Therefore, this study suggests that the transient landscape incision of the Ethiopian Plateau is largely controlled by the ongoing uplift of the plateau, indicating that the plateau physiography is dynamic, not stable.

Application of fractal and multifractal analysis on Blue Nile drainage patterns in the morphostructural analysis of the Ethiopian highlands, Ethiopia

“…The belt of SSA in the western part of Blue Nile Basin (Figure 6(d)) corresponds to the NW-SE direction of the Permo-Triassic fault system, which ran here (Macgregor, 2015). The young Quaternary character of the local drainage patterns with high FD and FDα is characterized by prevailing deep and narrow valleys, fault scarps, and the presence of morphodynamic phenomena (erosion, landslides, earthquakes) (Gani & Neupane, 2018). The drainage patterns are young and water divides change position easily (Kusák et al, 2019).…”

Assessment of relative tectonic activity using morphotectonic analysis in the Central High Atlas, Demnate Region, Morocco

“…11). In addition, average precipitation does not exceed 1000 mm/year under a semi-arid climate over most of the study area, which is suggested to be low to produce consensual slope breaks in stream profiles (Gani and Neupane 2018). Therefore, it can be suggested that current climatic conditions (precipitation) have no influence on the formation of the knickpoints detected in the Central High Atlas.…”

“…River longitudinal profile analysis usually examines topography in relation to tectonic forcing, climate, and lithology (Weissel and Seidl 1998;Clark et al 2004;Gani and Neupane 2018). For this purpose, normalized steepness (ksn) index is an indicator for fluvial incision triggered by the tectonic uplift, base-level change, climate, and lithology (Xue et al 2018).…”

“…Since, rivers' longitudinal profiles show an empirical power law relation between main channel slope and contributing drainage area expressed by the Eq. (6) (Hack 1973;Flint 1974;Wobus et al 2006;Gani and Neupane 2018):…”

“…For example, the linearity of mountain fronts and ratios of valley floor/height would be a good indicator of rates of uplift along a range bounding fault when effects of lithology and climate can be minimized (Bull and McFadden 1977). In the same way, to explore the relationships between uplift rates and landscape morphology, several researchers focused on the use of drainage networks analysis to decipher the role of neotectonics in the organization and architecture of rivers, the evolution of the landscape, and to assess earthquake hazard in different areas around the world (Wobus et al 2006;Nexer et al 2015;Xue et al 2017;Gani and Neupane 2018). Because of the advancement of geographic information systems (GIS) and the availability of data (DEM, satellite imagery, etc.…”