Mid-Pleistocene environmental change in tropical Africa began as early as 1.05 Ma

Palynological records from the Congo fan reveal environmental change in equ atorial Africa occurring 1.05 Ma ago, 100 k.y. before the mid-Pleistocene c limatic shift at 0.9 Ma. Prior to 1.05 Ma, a glacial-interglacial rhythm is not obvious in the African vegetation variation. Afterwards, Podocarpus sp read in the mountains of central Africa mainly during glacials and Congo Ri ver discharge decreased. The sequence of vegetation variation associated wi th the mid-Pleistocene glacials and interglacials differed from that observ ed during the late Pleistocene. Between 0.9 and 0.6 Ma, interglacials were characterized by warm dry conditions and glacials were characterized by coo l humid conditions, while during the past 0.2 Ma glacials were cold and dry and interglacials warm and humid. Our data indicate that before the Northe rn Hemisphere ice caps dramatically increased in size (0.9-0.6 Ma), low-lat itude climate forcing and response in the tropics played an important role in the initiation of 100 k.y. ice-age cycles. During the mid to late Pleist ocene, however, the climate conditions in the tropics were increasingly inf luenced by the glacial-interglacial variations of continental ice sheets.