Geomorphological processes and their palaeoenvironmental significance at the Shum Laka cave (Bamenda, western Cameroon)

The climatic-environmental history of the Shum Laka cave (western Cameroon) and its surroundings has been established by means of geomorphological, sedimentological and botanical data, tied in a well-dated stratigraphical sequence. Since ∼ 30,000 yr BP, this mountainous area (1,650–2,000 m ASL) has never been a desert, nor a tropical forest. Temperatures seldom significantly dropped below freezing. Mountain forest, with galleries along the water courses and grassland in between, prevailed most of the time. A certain evolution can be observed from ∼ 31,000 to ∼ 20,000 yr BP. Annual precipitation was initially higher than today, and subsequently somewhat lower. From 13,000 yr BP onwards, humidity and temperatures increased again. Around 9,000 yr BP they probably reached higher values than today. From 9,000 yr BP human activity became very apparent. This may have influenced the evolution of the natural landscape, and obliterated climatological effects. This evolution has been interrupted three times by dryer climatic conditions, which each time lasted for only 1 or 2 millennia, respectively at ∼ 33,000, at 11,000, and at ∼ 3,000 yr BP. Another important, less humid, episode occurred between 6,070 and 3,180 yr BP. Finally, there is some evidence for a drier period between 8,480 and 7,150 yr BP. The climatic evolution, established for the Shum Laka cave, confirms and refines former data from the area and is in good agreement with data from Barombi Mbo and Chad.