PRELIMINARY EVIDENCE OF VEGETATION CHANGE AROUND LAKE MALAWI, AFRICA OVER THE LAST 1.5 MILLION YEARS

Sediments recovered during the Lake Malawi scientific drilling preserve abundant plant micro- and macrofossils. Pollen is well-preserved and ubiquitous throughout the 1.5 million year sequence, and initial analyses of this pollen suggest the presence of past plant communities quite different from those surrounding the basin during the Holocene and Last Glacial Maximum (LGM). Most striking is the 20-30% of montane forest taxa grains (Podocarpus, Ericaceae, Hagenia spp., Asclepias spp. and Olea spp.) found in samples between 100 and 500 kyr BP as compared to the maximum montane percentages of 5% found during the Holocene and LGM. Pollen percentages of montane forest taxa, pteridophytes and sedges change consistently and in anti-phase with Poaceae, Evergreen forest taxa (Macaranga, Alchornea, Myrica, Celtis, and Faurea-type) and Moraceae. In addition to pollen, charred grass cuticle (greater than 150 micrometers in diameter) is present at select intervals within the sediment record. Ongoing carbon isotopic analyses of these cuticle fragments will augment the pollen results and provide additional insight into the nature and composition of the forest understory and open grassland plant communities. As additional data become available the results will be interpreted within the context of response to human and paleoclimatic forcing.