Palaeoenvironmental Reconstruction of the Late Pleistocene and Holocene in the Lake Chad Basin: A Multi-Proxy Record

The Lake Chad Basin in North East Nigeria recorded dramatic Pleistocene and Holocene environmental fluctuations associated with African monsoon variability, providing a critical archive for understanding natural climate variability over timescales relevant to projecting future hydrological change in this now-crisis-affected region. This study reconstructs the Late Pleistocene and Holocene palaeoenvironmental history of the Nigerian portion of the Lake Chad Basin using a multi-proxy sediment record from a deep sediment core recovered from the depocenter of a palaeo-lake in Borno State. A composite chronological framework combining radiocarbon dating, optically stimulated luminescence dating, and tephrochronological correlation provides age constraints across the core. Palaeoenvironmental proxies analysed include pollen assemblages, diatom assemblages, ostracod species composition, carbonate stable isotopes, grain size, magnetic susceptibility, and organic carbon content. Quantitative palaeoclimate reconstruction using transfer functions applied to diatom and pollen assemblages yields estimates of palaeoprecipitation and lake level variations through time. The study identifies the African Humid Period at approximately eleven to five thousand years before present as a period of dramatically enhanced monsoon precipitation and lake expansion, with abrupt termination consistent with a threshold response to declining insolation forcing. A revised palaeoclimate model for the Nigerian Lake Chad Basin is proposed and compared against regional synthesis datasets from Mali, Niger, and Cameroon. Keywords: palaeoenvironment, Lake Chad Basin, multi-proxy, Holocene, African Humid Period.