Climate change in the Turkana basin as deduced from a 4000 year long delta O-18 record

A model of the oxygen isotopic composition of Lake Turkana waters sheds insight into the paleoclimatic interpretation of a delta(18)O profile of inorganic calcite from a core taken from the lake. The model indicates that high frequency fluctuations seen in the isotopic record are probably due to shifts in lake level, while the long term increase of 1.4 parts per thousand seen from 4 to 2 kyr BP cannot be due solely to lake level change. It must be due to changes in other climatic parameters, such as the isotopic composition of the inflow, These findings suggests that the abrupt change observed in Lake Turkana (and many other African lakes) at 4 ka was the precursor to a 2000 year long adjustment in the climate over the Ethiopian Plateau. The isotopic record from Lake Turkana agrees with other paleoclimate records from the basin, including the diatom stratigraphy and radiocarbon dates on exposed shoreline deposits.