Paleolimnology of mid-elevation lakes in the Kenya Rift Valley

Abstract

Three small lakes of the Kenya Highlands have been subject to intermittent paleoenvironmental investigation for more than 50 years. In this report, the stratigraphic, core-based history of Lake Naivasha (elev. 1890 m) is extended backward to 20000 B.P. and is related to less complete 30000-year core stratigraphies from nearby lakes Nakuru and Elmenteita. The paleolimnological reconstructions, primarily diatom-based, include geochemical parameters and the first ostracode stratigraphies from tropical Africa. The analyses from all three lakes converge on a history of low and fluctuating water levels over approximately the past 4500 years, preceded by a major Holocene high stand (ca. 10000–6000 B.P.) and a brief earlier rise centered on 12500 B.P. The lakes were mostly very low during the late Pleistocene (13 000–30000 B.P.), though modestly elevated levels may have occurred early in this time period. The ostracode record, comprising at least 15 species, was relatively continuous in the Nakuru core but was restricted to sharply demarcated regions in cores from the other lakes.