2010 GSA Denver Annual Meeting (31 October 3 November 2010)
Paper No. 245-9
Presentation Time: 8:00 AM-6:00 PM


VAN PLANTINGA, Alexander, Department of Geology, Baylor University, One Bear Place #97354, Waco, TX 76798, alex_van@baylor.edu, PEPPE, Daniel J., Department of Geology, Baylor University, One Bear Place #97354, Waco, TX 76798-7354, TRYON, Christian, Department of Anthropology, Harvard University, Cambridge, MA 02138, and FAITH, J. Tyler, Hominid Paleobiology Doctoral Program, Department of Anthropology, George Washington University, Center for the Advanced Study of Hominid Paleobiology, Washington, DC 20052

The Pleistocene sediments of the Wasiriya Beds on Rusinga Island, Lake Victoria, Kenya were poorly understood geologically and archaeologically prior to renewed fieldwork in 2009. While work on Rusinga has traditionally focused on the famous Miocene fossils, our current work aims to clarify the previously conflicting reports of Pleistocene sediments preserving Late Pleistocene high lake-stand deposits, fossils of extant and extinct ungulates, and Middle Stone Age (MSA) artifacts.

Recent detailed stratigraphic work in the Wasiriya Beds has focused on the Nyamita locality, where > 31 m of sediment are exposed along an ~1 km transect. At Nyamita in situ and surface MSA artifacts and abundant vertebrate fossils have been documented and collected. Based on radiocarbon dates on gastropod shells, the Nyamita deposits are at least 43 ka, and possibly considerably older. The Wasiriya Beds at Nyamita are composed of sands, silty clays, conglomerate lenses, tuffaceous silts, and at least two cold spring carbonate (tufa) deposits. Exposed tuffaceous silt blocks contain fossil gastropods, weak ped structure, palesol carbonates and root casts. Several well-defined tuffaceous marker beds permit lateral correlation in the field and by geochemical compositional analyses by electron microprobe.

This study found no evidence of Pleistocene lacustrine facies, but instead indicates a complex paleoenvironment of alternating landscape stability and high-energy fluvial conditions, with Pleistocene topography similar to the modern situation: steep gulleys and sediment seasonally shed from local highlands ~2 km away. Further, these observations suggest that lake level during the deposition of the Wasiriya Beds was likely considerably lower than at present. The tufas imply a locally high water table and spring activity suggests some areas on Rusinga were wetter than the broader region. Abundant pedogenic carbonate nodules in the paleosols suggest a seasonal environment with periods of local aridity. Detailed stratigraphic control provides the foundation for a landscape-scale approach to paleoenvironmental and behavioral variability, and is the basis for our ongoing analyses using isotopic, ecological, and archaeological approaches to understand the behaviors of early Homo sapiens in the Lake Victoria region.

2010 GSA Denver Annual Meeting (31 October 3 November 2010)
General Information for this Meeting
Session No. 245--Booth# 9
Archaeological Geology (Posters)
Colorado Convention Center: Hall D
8:00 AM-6:00 PM, Wednesday, 3 November 2010

Geological Society of America Abstracts with Programs, Vol. 42, No. 5, p. 578

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