Extending the age model for Lake Bosumtwi (Ghana) to reconstruct West African climate and dust dynamics during the last million years

Lake Bosumtwi was created after a meteorite impact 1.07 Ma ago in an area that is highly susceptible for climate changes due to shifts of the tropical rain belt, as well as variation in dust dynamics. The sedimentary sequence records such changes in the tension field between the North African Monsoon (humid, wet) and the Harmattan (dry and dusty winds from the Sahara) and has been intensively studied. Drilling in 2004, supported by the International Continental Scientific Drilling Program (ICDP), recovered downhole logging data and sediment cores that allow for the analysis of the complete ~300 m lacustrine sequence. Yet, detailed climatic and environmental reconstructions for the record have not been completed, mostly due to the absence of a robust age model beyond 500 ka. In 2022, we obtained core scanning natural gamma ray data of the ~300 m lacustrine sedimentary sequence. Based on this data, we are generating an astronomical age model that can be directly compared to the 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 illuminate past changes in climate, environment, and ecosystems. This breakthrough 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.