Sediment cores and seismic reflection data acquired from the eastern basin of Lake Kivu, Rwanda reveal extensive limnologic variations due to changes in regional climate and basin structure. The eastern basin of the lake contains a sedimentary wedge which is > 1.5 km in thickness on its western side, and basal sediments are estimated to be at least 1.5 million years old. Sediments are likely to be thicker and older than this in the northern, Congolese basin of the lake. Above the ∼300 m iosbath only a thin layer of Holocene sediments are observed indication that this may have been the lake's high stand prior to that time. There are at least three erosional unconformities interpreted as desiccation or near-desiccation events which are estimated to have occurred at ∼475 ka, ∼100 ka, and ∼20 ka; the two most recent of these low stages likely developed during the African Megadrought and Last Glacial Maximum (LGM) periods. Following the LGM, the water levels rose to form a ∼100 m deep lake with its surface ∼370 m below the current lake level. The lake remained near that level for several thousand years and during this time the Virunga Volcanic Province expanded. At ∼12.2 ka a change to wetter climate conditions rapidly filled the lake to spill out of the Bukavu Bay basin southward toward Lake Tanganyika. Tephra sampled from the cores show that there have been at least 24 large local volcanic events since the early Holocene lake transgression.
Bibliographical noteFunding Information:
We thank the Government of Rwanda for permission to conduct this research, and to the Ministry of Natural Resources, the University of Rwanda, and Kivuwatt Ltd. for assistance with the field work. Financial support for the project was provided by Vanoil Energy Ltd. , the MacArthur Foundation , and the following industrial associates of the Syracuse University Rift Basin consortium: BP , Chevron , Shell , Petrobras , ExxonMobil and Cobalt International . Special thanks go to P. Cattaneo, J. Greenberg, J. Corbett, E. Kabende, and the crew of the R/V Kilindi. We extend special thanks to A. Vodacek for his leadership of the MacArthur Foundation project, and to X. Zhang, I. Nizere, D. Mburu, C.J. Ebinger, and R. Hecky, for support and scientific collaborations.
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- African Great Lakes
- East Africa Rift Valley
- East African climate
- Lake Kivu
- Virunga Volcanic Province