CLIMATIC CONTROL OF THE LATE QUATERNARY HYPERPYCNITE SEDIMENTOLOGY OF LAKE KIVU, EAST AFRICA

Lake Kivu, located in the Western Rift Valley of East Africa, is subject to various geologic hazards, including volcanic eruptions, earthquakes, and potential limnic eruptions due to magmatic charging of CO₂ in the hypolimnion. Integration of high-resolution seismic reflection data, radiocarbon-dated sediment cores, and lake-floor bathymetry of Lake Kivu reveals axially and transversely transported turbidite systems of the late Quaternary age in the Eastern Basin of the lake. Turbidity-flow depositional elements, including leveed-channels, overbank sediment waves, and terminal lobes, are observed. Sourced by hyperpycnal flows during floods, the temporal distribution of the turbidites is climatically controlled: the turbidite record (i.e. the turbidite bed-thickness time series) is well-correlated with the water level history of Lake Kivu, and the paleoclimatic and paleohydrologic records in tropical East Africa, over the past ~20 ka. Our work shows that turbidites sourced by hyperpycnal flows (i.e. hyperpycnites) are high-fidelity proxies for reconstructing past flood events, and provide a long-term measure of regional precipitation and lake level. It is also suggested, on the basis of the sediment stratigraphy, that exceptional floods may have triggered lake overturn events in Kivu’s recent history, with potentially catastrophic impact on aquatic fauna.