The modern Nile sediment system: Processes and products

摘要: Abstract We trace compositional changes of Nile sediments for 7400 km, from their sources in equatorial rift highlands Burundi and Rwanda to sink the Mediterranean Sea. All chemical physical controls on sediment petrography, mineralogy geochemistry, including weathering, grain-size, hydraulic sorting, mechanical breakdown, anthropic impact, mixing recycling are investigated detail. The course is controlled along its entire length by East African–Red Sea Rift. In this anorogenic setting, detritus derived various proportions volcanic fields associated with tectonic extension (Anorogenic Volcanic provenance) igneous, metamorphic sedimentary rocks uplifted shoulders or exposed craton (Continental Block provenance). spectrum such detrital signatures displayed catchment. Volcaniclastic Atbara sand generated focused erosion Ethiopian basaltic plateau semiarid climate, whereas quartzose White reflects low rates, extensive weathering trapping lakes swamps at subequatorial latitudes. main Nile, as tributary Blue suspended load volcaniclastic, feldspatho-quartzose bedload largely basement sources, fine medium-grained eolian added lower course. Mixing populations different provenance grain size reflected diverse violations settling-equivalence relationships fluvial deltaic sediments. Sediment delivery Sudan has been cut off after closure Aswan High Dam accelerated cusps leading local formation placer lags dominated ultradense Fe–Ti–Cr oxides, but mineralogical caused man's radical modification regimes have minor so far. beaches Sinai, Gaza Israel, volcaniclastic gets progressively diluted recycled coastal deposits carbonaticlastic eroded Levant shoulder. Studying variability modern big-river systems allows us appreciate richness natural processes occurring vast drainage basin, provides a key understand information stored archives reconstruct evolution Earth's surface recent less past.