Environmental Changes at Lake Cheshi, Zambia Since 40,000 Years B.P.

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Abstract
Sediment and microfossil analyses of a 7.5-m core from Lake Cheshi suggest that south-central Africa experienced late Quaternary climate changes similar to those in East Africa. The lake formed around 34,000 yr B.P., after a prelacustrine phase of at least 6000 yr, from climatic or tectonic causes. Ratios of precipitation to evaporation were probably similar to those of today until a decline about 15,000–13,000 yr B.P. when the lake shrank and became chemically concentrated. Maximal lake levels occurred between 8000 and 4000 yr B.P., and were followed by a low stand under presumably arid conditions about 3500 yr B.P. Encroachment of sudd vegetation contributed to shallowing during the last 3000 yr. A phase of microfossil dilution may reflect human activity in the basin, or climatic or hydrological changes. Melosira valve morphology seems to reflect mixing regimes. Sponge and testate amoeba remains were most numerous relative to diatoms during low-water phases.