Climatic and Hydrologic Changes in Northern Ethiopia in the last 3,500 Years: Evidence from the Geomorphic, Stratigraphic, and Geochemical Archives of Hayk Lake

Lake Hayk (23 km2 in surface) is located in northern Ethiopia, at an altitude of around 2,000 m a.s.l. The Late Holocene sedimentary successions preserved along the lake margins provide a detailed archive of the climate history of East Africa over the past 3,500 years. These successions are represented by colluvial/stromatolitic deposits and palustrine, deltaic, and fluvial sediments along the northern and southern coasts, respectively. During the last 3,500 years, the lake was characterized by three highstand phases, which occurred at about 3,250–3,000, 2,600–950, and 650 cal years BP—modern age (160 years BP non-calibrated). These stages are recorded by aggradation of siliciclastic deposits both along the southern and northern lake margins, whereas isotope data suggest that most of the stromatolites grew during phases of intense evaporation and lacustrine contraction. The good correlation between the Hayk Lake record and those of other late Holocene lakes of East Africa lakes allows a wide-scale generalization of late Holocene climate variability.