OSTRACODE OCCURRENCES AT EARLY HOMINID SITE, OLDUVAI GORGE, TANZANIA

Olduvai Gorge is prominent for discoveries of stone artifacts and hominin remains deposited in Pleistocene lacustrine, lake margin, and fluvial lithofacies in the Olduvai Basin of Northern Tanzania. Although ostracodes have been recorded at various localities near the shallow, saline-alkaline paleolake in the Olduvai Basin, no systematic study has been conducted. In July 2013, many localities in Olduvai Gorge Beds I-III (2.04 to 0.08 Ma) were surveyed and sampled where ostracodes were expected. Ostracodes were discovered and collected from locality 80 below tuff IID, locality 202 just above tuff IF, and locality 204 in beds III-IV (undifferentiated). Additionally, recent ostracodes were sampled from sediments of the shallow, oligosaline pond remaining in the Ol’Balbal Depression at Olduvai Gorge.

Most sampling was concentrated at locality 80 in sandy claystone in the western lake margin deposits. These samples were disaggregated by mechanically breaking the rock into fragments around 1.5 cm³ in size, pouring boiling water over the fragments, and often multiple freeze-thaw cycles. The sediment was sieved using 850 µm, 250 µm, 180 µm, and 150 µm mesh sieves and ostracodes were picked from the remaining material. At locality 80, preliminary results show 4 ostracode species that have not been previously described from Olduvai Gorge: Potamocypris sp., Cypridopsis vidua, Heterocypris incongruens, and Sclerocypris bicornis. This species assemblage indicates shallow water which is consistent with previous environmental interpretations of lake margin environments with streams and temporary saline ponds. Once additional samples are examined and identifications are confirmed with SEM images, differences in species composition among the sites can be assessed and more detailed lake subenvironments could potentially be identified. Future research into ostracode paleoecology at Olduvai Gorge localities can increase the understanding of hominin paleohabitats by helping to resolve the climate history associated with archaeological and paleontological finds.