Planning: CDP: High-Resolution Seismic Reflection Site Survey Supporting Lake Victoria Scientific Drilling

Syracuse University, Syracuse NY

Investigators

Abstract

2231128 Scholz This award will support acquisition of high-resolution seismic reflection data from Lake Victoria in East Africa. Several seismic lines are proposed (2000 km) over a two-year period in order to image the subsurface structure and stratigraphic framework of basinal lake sediments. The intent is to determine the best areas of the lake to drill as part of a future planned proposal to drill into lake sediment and recover long and continuous sedimentary records to facilitate studies of regional Pleistocene/Holocene paleoclimatology, paleoenvironments, and biologic history of the region and lake organisms. A CHIRP seismic reflection instrument would be towed by a contracted vessel. The data collected would be processed, analyzed, and interpreted and legacy seismic reflection data collected in the 1980 and 90s using older technology would be reprocessed, the data sets integrated and ultimately archived within the Marine Geoscience Data System (MGDS) at Lamont Doherty Earth Observatory. Planning activities and proposed seismic surveys are required to develop a future competitive proposal to conduct a scientific lake drilling campaign on Lake Victoria. The PIs are part of an international team of scientists who have already been supported by the International Continental Scientific Drilling Program to host a planning workshop in Tanzania in summer 2022. The proposed work would form the basis for the thesis work of an incoming Syracuse University graduate student who is a Tanzanian national and the work would be conducted in collaboration with Tanzanian institutions, including the Department of Fisheries, the Geological Survey Department, and the University of Dar es Salaam. Lake Victoria is the largest lake in Africa, is the source of the White Nile, is home to hundreds of endemic organisms, supports the largest lake fishery on Earth and contains important records of Quaternary climate variability in the continental tropics. Given its shallow, broad morphometry and large surface area- to- catchment ratio, the lake is extremely sensitive to changes in hydroclimate. Fluctuations in the water levels of the lake are important drivers for range expansion, contraction, fragmentation, adaptation, and diversification for flora and fauna in the lake (e.g., cichlid fish), as well as the broader watershed, and have contributed to the dispersal of early populations of Homo sapiens across Africa. Prior studies of lake sediment cores and seismic reflection data document the virtually complete desiccation of the lake at the terminal Pleistocene, and terrestrial outcrops within the lake’s watershed and seismic data from within the lake suggest the lake has likely desiccated and refilled multiple times in its approximately 400,000- year (~400 kyr) history. A future drilling program would support research on an array of topics, including 1) lacustrine basin formation and development, 2) tropical climate and environmental change over multiple glacial-interglacial cycles, 3) climate linkages to lake desiccation events, 4) diversification and evolution of aquatic fauna responding to lake dynamics and climate change, 5) climate and environmental pressures associated with lake extent driving dispersal of early human populations, and 6) savanna ecosystem changes and their biogeographic implications. The legacy seismic reflection data available from the lake are not suitable however for siting scientific drill cores from the basin, and this proposal will acquire modern, high- resolution ‘marine-type’ CHIRP seismic reflection data, which will image through the well-documented late Pleistocene unconformity present across the basin. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.