Evidence of forest extension in west Africa since 22,000 BP: A pollen record from the eastern tropical Atlantic
Résumé
Based on a pollen study of Atlantic deep-sea core KS12 (3°52'06" N-1°56'16 " W; 544 cm length; 2,955 m water depth) a continental paleoenvironmental reconstruction is proposed for the Gulf of Guinea for the time interval 22,000 BP--6500 BP. Repeated freshwater inputs by nearby coastal rivers were responsible for pollen transport from tropical humid environments during the whole period. Strong northerly trade circulation during the time interval 22,000-10,500 BP, with a maximum intensity at ca. 17,000 BP was responsible for pollen transport from Saharan and Sahelian environments which were located more to the south at that time. Near the coast, Guinean swamp and lowland forests were always present. They were particularly well developed around 22,000 BP, and later around 8,500 BP. After 17,000 BP, the progressive replacement of (semi)-arid elements (Saheliun and Saharun) by more humid Sudanian, Sudano-Guinean and Guinean associations indicates the onset of the modem vegetation zonation in West Africa.