Late Pleistocene and Holocene palaeohydrology of Lake Rukwa, Tanzania, inferred from diatom analysis

Diatom analysis has been used to provide information on the lake-level fluctuations of Lake Rukwa during the last 21.7 ka. Diatom-inferred chemical variables (conductivity, pH, anion and cation ratios) indicate that at the LGM lake level was low, probably driven by a low P:E ratio, but with sufficient water to avoid desiccation. Following the LGM, deep water conditions were obtained through a series of steps until maximum water depth was reached by at least 13.5 ka. The high lake-level phase lasted through the Early Holocene until after 6.7 ka. A shallow saline lake has occupied the basin from ca. 5.5 ka until the present day. The pattern of reconstructed lake-level fluctuation in Lake Rukwa is similar to that from Lake Tanganyika and other lakes from the equatorial and northern tropical zone. We can confirm that the N-tropical mode of millennial scale lake-level change since the LGM extended to at least 8degreesS. (C) 2002 Elsevier Science B.V. All rights reserved.