Depositional environments in the White Nile Valley during the last 300,000 years

Abstract

Before regulation, the White Nile contributed 83% of the low water flow to the main Nile and was responsible for maintaining the Nile as a perennial river during times of drought in Ethiopia. Two key unresolved questions relating to the White Nile are:        (a) When did the White Nile first join the main Nile?        (b) What type of sediment did the White Nile contribute to the main Nile? The answer to the first question has important implications for our understanding of hydro–climatic and tectonic events in the Ugandan Lake Plateau. The answer to the second question is essential for correctly interpreting the sedimentary record preserved in the Nile deep sea fan in the eastern Mediterranean. Our work has shown for the first time that the White Nile has been transporting smectite–rich sediments from the time of its probable inception over 240 ka ago and possibly since about 400 ka. Our analysis of the heavy mineral assemblages in White Nile alluvial sediments provides strong support for a source in the Lake Plateau region of Uganda. The White Nile was flowing from Uganda by at least 240 ka and very likely from about 400 ka.