PALEOENVIRONMENTAL RECONSTRUCTION OF THE HOLOCENE GALANA BOI FORMATION AT KABUA GORGE, TURKANA BASIN, KENYA

The Late Pleistocene to Holocene Galana Boi Formation records the transgressive/regressive cycles of Lake Turkana in response to the climatic changes during the African Humid Period. The migrations of the lake-margin impacted the paleoenvironment in which anatomically modern humans lived. Using a series of new stratigraphic sections, this study provides a high definition paleoenvironmental reconstruction of the Galana Boi at Kabua Gorge, which is located approximately 12 km southwest of the town of Kalokol. In addition to measuring sections, fieldwork in the summer of 2016 involved collecting samples for lab analyses such as δ¹³C and δ¹⁸O, loss on ignition, radiocarbon dating, and singe shard tephra geochemistry. Localized (on the order of 10’s of m) spatial and temporal facies variability indicates a highly dynamic lake-margin environment. A laterally extensive unit of black clay serves as a key stratigraphic marker bed at Kabua Gorge, and represents a reducing marsh environment that would have provided abundant resources for exploitation. The presence of pedogenic carbonate nodules and vertic features suggests that some areas of black clay were subaerially exposed, resulting in Vertisol formation of up to 5 m thick. However, the degree of pedogenic overprint varies laterally within the unit, with the northern portion showing more developed pedogenic features. Distal to the Kalokol River the strata become more diatomaceous as a result of a decrease in terrigenous input. The measured section referred to as KLS is capped by alternating intervals of sand and diatomaceous silt/diatomite, representing a fluctuation between beach and lacustrine depositional environments respectively. A better understanding of these dynamic systems and the resulting sub-environments provides insight into the paleoenvironmental context and resources available to anatomically modern humans. In addition, the Galana Boi Formation records an important period in the migration of anatomically modern humans through the Nile drainage network, which served as a passageway through the otherwise arid environment of East Africa.