Role of dynamic topography in sustaining the Nile River over 30 million years

Hagenia from the early Miocene of Ethiopia: Evidence for possible niche evolution?

“…The data produced by our study of early Faccenna et al (2019) suggest the elevation at Mush would have been as high as 2,500. Nevertheless, the paleoflora is interpreted as a closed-canopy, mixed-moist semi-evergreen forest described from the modern Guineo-Congolian lowlands with average yearly precipitation of about 1500-1600 mm (Bush et al, 2017).…”

“…The consensus opinion from a variety of studies indicates deposition into the Nile Delta of sediments originating on the Ethiopian Plateau beginning in the late Oligocene nearly contemporaneously with massive flood basalt eruptions, indicating a topographic high relative to the delta region (Faccenna et al, 2019;Fielding et al, 2018;Ismail & Abdelsalam, 2012;Macgregor, 2012;Pik et al, 2003;Sembroni et al, 2016). Most studies, whether using remote sensing coupled with nickpoint geomorphology or thermochronometry (e.g., U-Th/ He), conclude that the Blue Nile has been the main, if not only, source of sedimentation to the Nile Basin since the late Oligocene, and additional episodes of elevation took place between about 22 and 10 Ma (Pik et al, 2003;Sembroni et al, 2016;Fielding et al, 2018;Faccenna et al, 2019). Ismail and Abdelsalam (2012) Paleoclimate at the Mush locality has so far been documented by calculation of mean annual precipitation from leaf morphology at six stratigraphic horizons, including the specific location of deposits also preserving Hagenia pollen (Bush et al, 2017).…”

The First Fossil Owl (Aves, Strigiformes) From the Paleogene of Africa

“…Likewise, loss of the mammalian megafauna in North and South America has been implicated as a potential contributing factor in the extinction and reduction of giant scavengers, such as the teratorns and condors [64,65]. Additionally, new evidence suggests that the Nile River drainage system formed contemporaneously with the estimated age of Jebel Owl (~30 Ma; [66]) and the subsidence of northern Egypt and changing environment of that time period may have played a role in the creation of the niche occupied by this large owl. However, additional information regarding the geographic and temporal distribution of the Jebel Owl will be needed before paleoclimatic and faunal impacts can be assessed with any certainty.…”

Scale‐Dependent Flow Directions of Rivers and the Importance of Subplate Support

“…To explore whether subplate forcing can “overwrite” the effects of preexisting structure we use landscape evolution models. A similar problem has been examined by parameterizing landscape evolution models using uplift predicted from “backwards in time” global convection models (Braun et al., 2013; Faccenna et al., 2019). Our approach has three steps.…”

“…The planform of rivers on top of topographic swells in other continents also have similarly simple patterns at long, O(10 3 –10 4 ) km, wavelengths (Rudge et al., 2015). At these long wavelengths rivers mostly flow away from crests of topographic swells that are supported by the mantle (Braun et al., 2013; Faccenna et al., 2019; Roberts et al., 2012). This pattern of emergent simplicity at long wavelengths is manifest in the flow paths of many large rivers draining topographic swells and tectonic topography on Earth, for example, African swells, Colorado Plateau, Mexican Highlands, East Australian Highlands, Himalayas, and elsewhere, for example, Tharsis Rise, Mars (Black et al., 2017).…”