The Kashiru Pollen Sequence (Burundi) Palaeoclimatic Implications for the Last 40,000 yr B.P. in Tropical Africa

Abstract

A continuous pollen record from a central African highland site (3°28′S, 29°34′E) with 15 radio-carbon dates spans at least the last 40,000 yr. Both modern and fossil pollen have been investigated. A clear pattern of changes in vegetation and climate is suggested. Prior to 30,000 yr B.P., the occurrence of the montane conifer forest, including the upper forest limit, indicates climatic conditions colder and drier than now, but more humid than in late-glacial time. Between 30,000 and 15,000 yr B.P., grassland with afroalpine indicators expanded down to 2500-2000 m altitude as a result of dry, and most probably cool, climate; the montane forest persisted in refuges, although much reduced. Forest vegetation with the same floristic composition as today appeared after 13,250 ± 200 yr B.P., suggesting more humid conditions. The occurrence of a possible short-term humid episode about 21,500 yr B.P. is correlated with some high lake-level stages in East Africa and with organic deposits in deep-sea cores from the Mediterranean and the Atlantic Ocean.