Paleoclimate implication on the Lake Fonjak level changes (Adamawa Plateau, Central Cameroon) during the last 13,500 cal yr BP

Abstract

A significant change towards more arid/seasonal climate conditions in the transitional zone between equatorial and sahelian zones in Central Africa was clearly recorded in the Lake Fonjak, Adamawa plateau. In the aim of taking out the implication of paleoclimate variations on lake level changes in the Adamawa plateau during the Holocene, diatoms records coupled with C/N ratio and P content in the Lake Fonjak sediments were studied. They exhibit three zones related to the water level variations since 13,500 cal yr BP. From 13,500 to 4400 cal yr BP, the zone I evidences the predominance of planktonics, suggesting a high-water level in the Lake Fonjak at this period. From 4400 to 3600 cal yr BP, the zone II shows the appearance of tychoplanktonics, followed by the rise of both aerophilous and epiphytics, indicating the lake level oscillations at centennial timescale with shallow water and dried areas in the borders. Beyond 3600 cal yr BP, the zone III corresponds to the rise of both benthics and aerophilous, suggesting an important lowering of the water-level until sub-modern conditions. These changes are linked to the displacement ITCZ mean positions in the context of the decreasing summer insolation in the northern hemisphere.