The Quaternary landscapes, chronostratigraphy, and paleoenvironments of the Chalbi Desert, Kenya

Abstract The Chalbi Desert, located in eastern Africa, is a significant but overlooked archive of the Pleistocene and Holocene periods that could add insight into investigations on human evolution. We revisited southeastern Chalbi Desert landforms between the towns of Kargi and Maikona to improve the chronostratigraphy and provide paleoenvironmental context. Direct U-series and electron spin resonance dating of various fossil teeth recovered from a deflated dune (Qzs) landform at the Farre locality return a mean age of ∼545 ka, which is compatible with biostratigraphic inferences. While this numerical age result should probably be regarded as mostly indicative given the existing uncertainty on the environmental dose rate evaluation, the data set available nevertheless strongly suggests a Middle Pleistocene age for at least some of the fauna. Sedimentology, luminescence, and 14 C dating further suggest that this Qzs landform and its contents were modified by alluvial fan development and weathering during denudation in a proximal fan setting through the late Pleistocene into the Holocene. The Qzs landform currently experiences aeolian additions, erosion, and salt-affected soil development in an arid climate. Pedogenic carbonate isotope geochemistry suggests that deflated sand dunes were covered by woody grasslands during Marine Isotope Stage (MIS) 4 and 3 pluvials, consistent with nearby fan progradation constrained at >35 ka. The desert experienced increased hydrologic activity during late Pleistocene and African humid period pluvials, as evidenced by additional optically stimulated luminescence and 14 C dating from fan, dune, and playa contexts. The last significant pluvial episode ended after 4.4 ± 0.3 cal ka BP, which coincides with the final regression of nearby Lake Turkana. This study extends the chronology of Quaternary sediments in the Chalbi Desert to the Middle Pleistocene and offers paleoenvironmental insights into the conditions experienced by Middle Stone Age tool users in the region.