Pollen and isotopic records in Late Holocene sediments from Lake Turkana, Kenya

A 12 m piston core (LT 84-8P) taken in the northern basin of Lake Turkana has been dated by 6 AMS radiocarbon dates on large ostracods and analysed for its pollen content. During the past 2500 years, the pollen assemblages were dominated by Chenopodiaceae/Amaranthaceae (Cheno/Am) and Gramineae, representing the local pollen signal of the surrounding vegetation under arid conditions. Percentage fluctuations of Cheno/Am are interpreted as reflecting lake level variations in good correspondance with oxygen isotope from the same core. A rise in lake level is recorded at about 1600 yr B.P., preceded by a relative lowstand during much of the period from 2500 to 1600 yr B.P. The top of the core is estimated to be about 600 yr old, and shows a shift of unknown duration towards a more humid condition. The high lake level documented in this paper roughly coincides with that reconstructed from other cores in the lake based on diatom and carbonate analyses.