Extending the age model for Lake Bosumtwi (Ghana) for climate- and environmental reconstructions in West Africa during the last million years

Lake Bosumtwi, formed after a meteorite impact at ~1.07 Ma, contains a sedimentary archive that yields an excellent high-resolution record of climate- and environmental change in Sub-Saharan West Africa. The region is highly susceptible to climate changes due to shifts of the tropical rain belt and variation in dust dynamics in the tension field between the North African Monsoon (humid, wet) and the Harmattan (dry and dusty winds from the Sahara). Consequently, Lake Bosumtwi has been intensively studied and in 2004, supported by the International Continental Scientific Drilling Program (ICDP), sediment cores were recovered and downhole logs were performed that allow for the analysis of the complete ~300 m lacustrine sequence. However, detailed climatic and environmental reconstructions for the record are incomplete, mostly due to the absence of a robust age model prior to 500 ka. In 2022, we conducted core scanning natural gamma ray measurements for the ~300 m lacustrine sedimentary sequence. Based on the resulting data, we are generating a correlative age model that is tested by cyclostratigraphic tools and that can be directly compared to the available independently dated sections, but extends farther back in time. Our age model will provide critical chronologic context for the numerous existing and new proxy data that facilitate a study of changes in climate, environment, and ecosystems. This will allow a robust framework to analyse climatic interferences with archaeological findings that might shed new light on habitat availability for our ancestors in tropical Western Africa.