Kathryne Fogle, “Analysis of Sediments Cores from Lake Basin of Olduvai Using X-ray Diffraction”
Mentor: Lindsay McHenry, Geosciences
Olduvai Gorge in Tanzania, East Africa is important anthropologically and has provided information on key phases on early human evolution and vertebrate fauna during the Pleistocene epoch from 2 Ma and 11,700 Ka[LJMI] and also hosted a lake during most of its history. The mineralogy of a paleolake sediment core (2A) sampled between 31 and 44 meters below the surface was analyzed using X-ray Diffraction (XRD) and interpreted to determine changes in sediment sources and lake water chemistry. Changes in water composition are indicated by fluctuating amounts of carbonate materials. All samples but one contain the zeolite mineral analcime and its fluctuating abundance indicate changes in water chemistry. From 33.18 to 34.46 meters of core 2A analcime is abundant but for the next 3m above it is less detectable. Finer claystone intervals seem to have a higher abundance in analcime, while zeolite is less abundant in clay-sand layers. In core 2A at 37.14 m and ending at 39.5 m in depth dolomite is abundant where analcime and other zeolites are less detectable, which may indicate a possible influx of Mg and lower pH. These findings are consistent with an arid environment with a saline-alkaline lake that is not suitable for human or animal consumption as high Ph and salinity are required to produce analcime.
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