Numerous rain forest and savanna terrains in Western Central Africa are located on flat planation surfaces formed by long lasting surface denudation over Gondwana type basement rocks, often topped by weathering resistant and extended lateritic crusts. There is widespread evidence and recognition that fluctuations in climate during the Quaternary in Central Africa have strongly affected regional environmental conditions such as extension, structure and composition of the rain forest-savanna border by modified rainfall and related hydrological characteristics. Equatorial

ecosystems in Africa can therefore be regarded as highly sensitive to former and recent environmental modifications (Gasse, 2000; Runge, 2001, 2002; Thomas, 2004). For palaeo-environmentally oriented studies the occurrence of thick alluvia trapped inside river basins can be successfully used as a proxy for former climate and vegetation reconstructions in lower latitudes (Thomas, 2000; Runge, 2002; Sangen, 2007).