PALEOCLIMATIC SIGNIFICANCE OF THE STABLE ISOTOPIC COMPOSITION AND PETROLOGY OF A LATE PLEISTOCENE STALAGMITE FROM BOTSWANA

High-resolution delta(18)O and delta(13)C analyses of a stalagmite fro m Lobatse II Cave reveal late Pleistocene environmental changes in Bot swana. Large shifts in delta(18)O and delta(13)C are observed between two main periods of deposition. The first period, between 51,000 and 4 3,000 yr B.P., was warm and humid and may have been associated with so me C-3 vegetation. The second period, between 27,000 and 21,000 yr B.P ., had temperatures approximately 2 degrees C lower, and vegetation do minated by drought-adapted C-4 plants. The intervening period, between 43,000 and 27,000 yr B.P., bounded by two major hiatuses in stalagmit e growth, produced discontinuous speleothem formation, probably under dry conditions. New Th-230/U-234 mass spectrometry age determinations for the stalagmite generally agree with previously measured Th-230/U-2 34 ages. (C) 1995 University of Washington.