A PRELIMINARY FOSSIL DIATOM ANALYSIS OF WEST TURKANA PALEOLAKE: THE HOMINID SITES AND PALEOLAKES DRILLING PROJECT (HSPDP)

We present preliminary results of the fossil diatom record from West Turkana Lake recovered from the HSPDP paleolake sediment core. The West Turkana site was chosen because of its great potential for reconstructing environmental variables that respond to climate change in the northeast African region during the period of early hominid activity. This 216-meter core was collected in the summer of 2014 from the western margin of the current Lake Turkana, above the modern lake level. The intermittent presence of lake sediments with fossil diatom assemblages in the core represents times in the past when the perimeter of the lake was more expansive, under more humid conditions. The presence of developing soil profiles in the core description infers multiple lake-level changes throughout the core. Diatom preservation worsens as alkalinity increases, which appears to coincide with the lower water levels. The Omo River is the major input to this terminal lake system and is currently located directly to the north of the Lake Turkana, northeast of this site. The location of this input is highly variable due to the high sediment loads and corresponding deltas. Variation in river position through time may have placed the mouth of the Omo River at or near this site and altered the diatom composition in the sediment record toward dominance of diatoms belonging to the genus Aulacoseira. Poor diatom preservation and few samples with abundant diatoms throughout the core have led us to change our original sampling interval strategy, focusing on core intervals with good diatom preservation at a finer resolution.