SEEING DEEPER INTO THE MUD: INSIGHTS FROM THE WTK13 CORE, WEST TURKANA, KENYA

A 215 m sedimentary core collected in 2013 from the Nachukui Formation, West Turkana, Kenya, presents a rare opportunity to integrate a multi-proxy core analysis with associated outcrop-based datasets and a rich record of hominin evolution. Age constraints from complimentary macro- and crypto-tephra characterizations constrain the core record to ca. 1.9 – 1.35 Ma, and permit tephrostratigraphic correlation around the basin. Lithostratigraphic details in the core demonstrate an unusually high-resolution facies record of lake-level fluctuations. Laminated clays alternate with weakly-developed paleosols throughout the core. High-frequency variation in water depths suggests Milankovitch and sub-Milankovitch scale climatic influences. Long-term variation observed in elemental XRF, TIC/TOC, biogenic silica, magnetic susceptability, and ostracod faunas document shifting environmental character as lacustrine dominance is supplanted by lake-margin processes.

The primary control for long-term environmental change may be more a function of landscape evolution (infilling of the lake), and may not be entirely a climatic signature. Short-term oscillations are almost certainly due to climatic dynamics within the basin and region, but operating over a wide range of temporal frequencies.

The environmental data from the WTK13 core can be directly linked to the important hominin KNM-WT 15000, the Turkana Boy skeleton, recovered barely 2.5 km from the coring site, as well as other significant paleontological and archaeological finds. The geological record reflected in the extremely well-preserved core sample also allows for a much more complete understanding of the implications of features seen in the more accessible outcrop record of the basin.

This work reflects contributions from all members of the Hominin Sites and Paleolakes Drilling Project (HSPDP) field and laboratory teams.