Cenozoic vegetation change in Africa : A large scale-view of a small-scale process.

JACOBS, B., PAN, A., SCOTESE, C., GARCÍA MASSINI, J.L.

Yaoundé, Cameroon.

Congreso; 18th meeting of the Association for the Taxonomic Study of the Flora of Tropical Africa (AETFAT); 2007

Abstract Efforts to improve a spatially and temporally uneven paleobotanical record have produced Eocene, Oligocene, and Miocene sites in Tanzania, Ethiopia, and Kenya. A 46 Ma site demonstrates northern Tanzania had a dry climate similar to today, and woodlands dominated by microphyllous, caesalpinioid legumes – structurally similar to modern woodlands. Paleobotanical sites on the Ethiopian Plateau, 28-27 Ma, document forests with genera found today (disjunct) in West Africa, and coastal and Eastern Arc Mountains of Kenya and Tanzania, but now absent from Ethiopia. The common occurrence of palm fossils indicates the forests differed from living counterparts, where palms are absent or species-poor. A decline in the ecological role for palms took place after 27 Ma, but a decrease in palm diversity seems to have occurred before 28 Ma as palm genera identified are found in Africa today. The Miocene record from Kenya indicates considerable variation in environments between 12.6 and 7 Ma, ranging from lowland forests with West African affinities, to seasonally dry, legume-dominated woodland or wooded savannah. These demonstrate that the overall trend toward increasing aridity and spreading grass-dominated environments during the Neogene was complicated by smaller-scale variations in landscape and vegetation in the East African rift.