Lithological stratigraphies of 210Pb-dated sediment cores from four hydrologically interconnected fluctuating lake basins in Kenya are used to investigate how differences in basin morphometry and physical limnology influence the preservation and time resolution of sedimentary climate-proxy records. The potential of lakes to accumulate an undisturbed sediment record is primarily determined by their relative depth, the ratio between maximum depth and effective wind fetch. Chemically stratified crater lakes accumulate high-quality climate-proxy records because they complement great relative depth with topographical wind shelter, resistance of density stratification to propagation of wind-induced turbulence, and absence of bioturbation in anoxic bottom waters. The changes in water-column circulation and bottom dynamics that accompany lake-level fluctuations affect the time resolution of accumulating climate-proxy signals and thus the apparent magnitude and frequency of inferred climatic events. An episode of low lake level can be both over- or underrepresented in the climate-proxy record depending on the severity of the drawdown relative to the lake's critical depth of sediment accumulation. Decade-scale hiatuses due to non-deposition or erosion at low lake level may be difficult to recognize because mixing of unconsolidated muds deposited before and after the lowstand can obliterate evidence that the record has been truncated. Regional correlation of climate-proxy records must consider both hydrology-related differences in the climatic sensitivity of lakes and sedimentation-related differences in the integrity of their climate-history archive.
|Original language||English (US)|
|Number of pages||17|
|Journal||Quaternary Science Reviews|
|State||Published - May 1999|
Bibliographical noteFunding Information:
This study was funded by NSF-DEB 93-20324, NSF-ATM 95-31222, NSF-RTG 90-14277, and the Quaternary Paleoecology program at the University of Minnesota. The Þeldwork was carried out with research permission from the Office of the President of the Republic of Kenya to K. M. Mavuti (University of Nairobi). I thank Ken Mavuti, David Harper, Nicola Pacini, Brigitta Ammann, Herb Wright, Fabienne Janssen, Jo Verschuren, and officials at the Kenya Power and Lighting Co. and the Olkaria Geothermal Co. for assistance in the Þeld, Lady S. Cole and Melvyn Carnelley for historical information, Dan Engstrom for access to 210Pb-dating facilities, and Kerry Kelts, Tom Johnson, and David Williamson for comments on the draft manuscript. The author is postdoctoral fellow in Climate and Global Change Research with the National Oceanic and Atmospheric Administration (USA) and the Fund for ScientiÞc Research (Flanders, Belgium), and acknowledges predoctoral fellowships from the Belgian—American Educational Foundation and the Graduate School of the University of Minnesota. This is Limnological Research Center contribution No. 516.
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