Late Holocene palaeolimnology of Bal Lake, Northern Nigeria, a multidisciplinary study

A multidisciplinary study of lake sediments from Bal Lake, a small saline lake in the Sahel zone of northeastern Nigeria, provides evidence for changing precipitation/evaporation ratios over the last 1000 cal. years. Climatic and environmental changes over this period have been reconstructed using evidence from ostracod faunal assemblages and shell chemistry, sediment properties and palynology and the sequences dated by a combination of 137Cs, 210Pb and AMS radiocarbon methods. The results testify to major hydrological changes in the Sahel over the last millennium. The end of a major drought phase that is seen in other records from the Manga Grasslands is dated to around 950 AD. This was followed by a prolonged freshwater phase of the lake from the 12th to the 16th century AD which points to wetter conditions. A period of higher salinity and hence drier and more variable conditions from the 1700s to the mid-1900s was followed by a pronounced drying trend into the 20th century.