A mid to late Tertiary lake, Palaeolake Etosha, was the single collective end point of three drainage systems feeding southwards off the central Angolan highlands, the Cubango and Kunene Megafans and the Cuvelai Drainage System. The lake beds consist of 50 m of saline, olive green clay, the Etosha Pan Clay Member, containing authigenic analcime, monoclinic K-feldspar and glauconite.