A 12,400 C-14 yr offshore diatom record from east central Lake Victoria, East Africa

The diatom record of V95-2P, a 7.6 m long sediment core collected from 67 m depth, is the first from the east central portion of Lake Victoria. A soil horizon developed at the coring site shortly before 12,400 C-14 yr BP due to a lakewide desiccation event. The radiocarbon chronology of the older ha lf of this core is problematic, but if our estimated chronology is correct, then aridity and evaporative concentration of the lake are indicated by th e presence of Thalassiosira rudolfi from > 12,400 BP to about 10,000 BP. Ab undant Aulacoseira and generally rising biogenic silica concentrations may reflect enhanced water column mixing and rising precipitation:evaporation r atios ca. 10,000-8400 BP. A lakewide reorganization of diatom assemblages o ccurred around 7200 BP, when Aulacoseira nyassensis largely replaced A. gra nulata and after which rainfall and wind-driven mixing became more seasonal ly restricted. Pronounced reductions in offshore diatom deposition, from ab out 8300-5800 BP and after 3500 BP, may have been related to declines in th e duration and/or intensity of wind-driven mixing. Increased aridity, and p ossibly deforestation in the lake basin, is indicated after 1400 BP.