GRAIN SIZE ANALYSIS OF THE WEST TURKANA KAITIO (WTK13) CORE AND IMPLICATIONS FOR PALEOENVIRONMENTS IN THE TURKANA BASIN 1.8 TO 1.3 MA

Grain size data is an important component of sedimentological analysis that can provide insight into the energy and conditions of the depositional environment. When combined with other proxy records, grain size analysis furthers paleoenvironmental reconstructions through time. The Hominin Sites and Paleolakes Drilling Project (HSPDP) collected a core (WTK13) from the Turkana Basin in northwestern Kenya that records environmental conditions over the period 1.8-1.3 Ma. The target of this core was the fine-grained lithology of the Lorenyang Lake and the record is directly correlated to hominin find KNM-WT 15000 (Turkana Boy). WTK13 is primarily composed of fine sediment, specifically clays and silts. However, it coarsens in the upper 60 m. The facies record of this core and other proxy record data sets indicate lake level fluctuations in a dynamic lake margin environment. The sample collection process involved collecting sediment samples from approximately 32 cm intervals along the length of the 216 m core for high-resolution analysis. Additionally, we sampled through laminated and scrambled facies associations which represent flooding surfaces of the lake across moderate to weakly developed paleosols. Samples were run on a Malvern Mastersizer 3000 after removing carbonates, organics, and biogenic silica. Silt dominates both paleosols and laminated intervals with about 20-30% sand and <10% clay. Comparison of grain size data to other proxy record data sets from WTK13 using spectral analysis can uncover important trends in depositional environment throughout the lake’s history. A detailed grain size analysis of the WTK13 core demonstrates otherwise undetectable variability in the Turkana paleolake sediment. These trends provide insight into the energy of the depositional environment of paleolake Turkana and thus the landscape hominins inhabited.