Reconstructing the Environmental Context of Human Origins in Eastern Africa Through Scientific Drilling
Annual Review of Earth and Planetary Sciences, 50451 – 476 2022ISSN: 00846597 Publisher: Annual Reviews Inc.
Keywords:▾ Africa; Core drilling; Drills; Infill drilling; Sedimentary rocks; Stratigraphy; Continental scientific drillings; Drill core; East African Rift; Eastern Africa; Environmental contexts; High resolution; Hominins; Human evolution; Late Neogene; Paleoclimates; environmental change; environmental history; human evolution; Neogene; paleoclimate; Pleistocene; Lakes
Abstract: ▾ Paleoanthropologists have long speculated about the role of environmental change in shaping human evolution in Africa. In recent years, drill cores of late Neogene lacustrine sedimentary rocks have yielded valuable high-resolution records of climatic and ecosystem change. Eastern African Rift sediments (primarily lake beds) provide an extraordinary range of data in close proximity to important fossil hominin and archaeological sites, allowing critical study of hypotheses that connect environmental history and hominin evolution. We review recent drill-core studies spanning the Plio-Pleistocene boundary (an interval of hominin diversification, including the earliest members of our genus Homo and the oldest stone tools), and the Mid-Upper Pleistocene (spanning the origin of Homo sapiens in Africa and our early technological and dispersal history). Proposed drilling of Africa's oldest lakes promises to extend such records back to the late Miocene. squf High-resolution paleoenvironmental records are critical for understanding external drivers of human evolution. squf African lake basin drill cores play a critical role in enhancing hominin paleoenvironmental records given their continuity and proximity to key paleoanthropological sites. squf The oldest African lakes have the potential to reveal a comprehensive paleoenvironmental context for the entire late Neogene history of hominin evolution. © 2022 by Annual Reviews. All rights reserved.
The Lake Chad hydrology under current climate change
Scientific Reports, 10 (1) 2020ISSN: 20452322 Publisher: Nature Research
Abstract: ▾ Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s. Despites a partial recovery in response to increased Sahelian precipitation in the 1990s, Lake Chad is still facing major threats and its contemporary variability under climate change remains highly uncertain. Here, using a new multi-satellite approach, we show that Lake Chad extent has remained stable during the last two decades, despite a slight decrease of its northern pool. Moreover, since the 2000s, groundwater, which contributes to ~70% of Lake Chad’s annual water storage change, is increasing due to water supply provided by its two main tributaries. Our results indicate that in tandem with groundwater and tropical origin of water supply, over the last two decades, Lake Chad is not shrinking and recovers seasonally its surface water extent and volume. This study provides a robust regional understanding of current hydrology and changes in the Lake Chad region, giving a basis for developing future climate adaptation strategies. © 2020, The Author(s).
The Lake CHAd Deep DRILLing project (CHADRILL) - targeting ~ 10 million years of environmental and climate change in Africa
Scientific Drilling, 2471 – 78 2018ISSN: 18168957 Publisher: Copernicus GmbH
Keywords:▾ Biodiversity; Boring; Deposition; Infill drilling; Lakes; Sediments; Water levels; Continuous sequences; Depositional environment; Environmental records; Intertropical convergence zone; Microbial biodiversity; Monsoon circulations; Pleistocene sediments; Subsurface biosphere; Climate change
Abstract: ▾ At present, Lake Chad ( ~13°0 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 intertropical convergence zone (ITCZ) and monsoon circulation leading to a peak in rainfall during boreal summer. During recent 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 673m long geotechnical borehole drilled in 1973, along with outcrop and seismic reflection studies, reveal several hundred metres 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 northern African hydroclimate under different climate boundary conditions such as high CO2 and absence of Northern 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 migrations across northern Africa and has major implications for understanding human evolution. Furthermore, due to its dramatic and episodically changing water levels and associated depositional modes, 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 microbial biodiversity present in this type of depositional environment. We propose to drill a total of ~1800m of poorly to semi-consolidated lacustrine, fluvial, and eolian sediments down to bedrock at a single on-shore site close to the shoreline of present-day Lake Chad. We propose to locate our drilling operations on-shore close to the site where the geotechnical Bol borehole (13°280 N, 14°440 E) was drilled in 1973. This is for two main reasons: (1) nowhere else in the Chad Basin do we have such detailed information about the lithologies to be drilled; and (2) the Bol site is close to the depocentre of the Chad Basin and therefore likely to provide the stratigraphically most continuous sequence. © Author(s) 2018.