At present, Lake Chad (~13°’N, ~14°E) is a shallow freshwater lake located in the Sahel/Sahara region of central northern Africa. The lake is primarily fed by the Chari-Logone river system draining a ~600,000 km2 watershed in tropical Africa. Discharge is strongly controlled by the annual passage of the ITCZ and monsoon circulation leading to a peak in rainfall during boreal summer. During the past decades, a large number of studies have been carried out in the Lake Chad Basin (LCB). They have mostly focused on a patchwork of exposed lake sediments and outcrops once inhabited by early hominids. A dataset generated from a 673 m long geotechnical borehole drilled in 1973, along with outcrop and seismic reflection studies, reveal several hundred meters of Miocene-Pleistocene lacustrine deposits. CHADRILL aims to recover a sedimentary core spanning the Miocene-Pleistocene sediment succession of Lake Chad through deep drilling. This record will provide significant insights into the modulation of orbitally forced changes in North African hydroclimate under different climate boundary conditions such as high CO2 and absence of N-Hemisphere ice sheets. These investigations will also help unravel both the age and the origin of the lake and its current desert surrounding. The LCB is very rich in early hominid fossils (Australopithecus bahrelghazali; Sahelanthropus tchadensis) of Late Miocene age. Thus, retrieving a sediment core from this basin will provide the most continuous climatic and environmental record with which to compare hominid migration(s) across northern Africa and has major implications for understanding human evolution. Furthermore, due to its dramatic and episodically changing water levels, Lake Chad’s sediments resemble maybe an analogue for lake systems that were once present on Mars. Consequently the study of the subsurface biosphere contained in these sediments has the potential to shed light on early life on Earth and other planets. Our preliminary drilling plan involves a multi-site approach with deep holes in the southern basin at easily accessible and protected sites to recover Miocene-Early Pleistocene deposits. Known outcrops encompassing deposits of maximum lake extent will be targeted by shallow drilling to the north. In this proposal, we are requesting funds to organize an ICDP workshop in N’Djamena (Chad) in 2015, to refine the current drilling plan, extend the research goals of the project, and to broaden the science team working on CHADRILL.
Sylvestre, Florence , Schuster, Mathieu , Vogel, Hendrik , Abdheramane, Moussa , Ariztegui, Daniel , Salzmann, Ulrich , Schwalb, Antje , Waldmann, Nicolas , and the ICDP CHADRILL Consortium (2018). "The Lake CHAd Deep DRILLing project (CHADRILL) – targeting ~10 million years of environmental and climate change in Africa" Scientific Drilling 24 p71-78