A direct comparison between the historical record of lake level and the d18O signal in carbonate sediments from Lake Turkana, Kenya

Ricketts, Richard D., Robert F. Anderson

Limnol. Oceanogr., 43(5), 1998, 811-822 | DOI: 10.4319/lo.1998.43.5.0811

ABSTRACT: We compared oxygen isotopic profiles from authigenic calcite in nine freeze cores from Lake Turkana, Kenya, with the historical record of lake levels for the past 105 years. 210Pb dating of the cores indicates that sediment in two of the cores spans the complete historical record. We observed spatial variability in δ18O and δ13C values between cores and an offset from expected isotopic equilibrium values in several of the cores. Both of these characteristics can be explained by proximity to river input. In model calculations of lake level, we muted the spatial variability of the S1*O dataset by using a normalized and stacked record. There is good agreement between the lake level history modeled using the normalized and stacked record and the historical record of lake level. The lake level record derived from the δ18O data indicates that lake level fluctuated by 15 m during the last century. Our model calculations indicate that δ18O records can be used to generate quantitative lake level curves even using datasets with significant spatial variability.

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