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Accepted Paper:

High frequency lake cycles at Olduvai Gorge, Tanzania, significance in hominin evolutionary studies and drillcore correlation.  
Ian Stanistreet (The University of Liverpool) Nicholas Toth (University of Indiana) Kathy Schick (University of Indiana) Lindsay McHenry (University of Wisconsin- Milwaukee)

Paper short abstract:

Measurement of East African palaeoclimatic variation has concentrated on drying/wetting cycles of Milankovitch band. We explore higher frequency lake advance/withdrawal cycles on millenial scales, helping to identify palaeo-land surfaces, and allowing highly resolved correlation with lake drillcores.

Paper long abstract:

Measurements of East African palaeoclimatic variation have so far concentrated on drying/wetting trends of the Milankovitch spectrum (>23,000a). However very high frequency (multimillenial) sub-Milankovitch cycles of lake flooding have been identified at Olduvai Gorge and have been termed Lake-parasequences, analogous to marine parasequences of Milankovitch period. These have previously been applied to the high-resolution correlation of hominin assemblage levels, such as HWK E Level 1 and FLK Level 22. We use these high frequency lake cycles to demonstrate our ability to identify palaeo-land surfaces over wide areas and correlate between drillcores and sites of interest to human origins studies. Our current test interval to apply Sequence Stratigraphic concepts concerns the sections between the Bed I Basalt and Tuff IB, including Leakey's well-known "living floor" at DK. Derived from trench backwalls, a high-resolution trench- and outcrop-based stratigraphic framework defines successive land surfaces, allowing their correlation with recently drilled Borehole 2A, sited in an offshore lake setting. Bracketing this interval are the Bed I Basalt (1.877+0.013 Ma), prominent in core 2A, and Tuff IB (1.848+0.003 Ma), confirmed geochemically. Since there are no major tuffs in the core between these two units, the Sequence Stratigraphic methods were required to provide ties within. The full import of this technique comes with the challenge to relate hominin sites and transitional surfaces to predominantly lacustrine borehole core sediments. Whereas facies cannot be correlated easily, Lake-parasequences can. As a pilot study we have undertaken correlation of the DK assemblage surface, previously excavated by us, to Borehole 2A. [Additional authors N. Toth & K. Schick]

Panel P24
Climate change, technology and palaeobiology in early hominin evolution
  Session 1