Hydroclimate reconstructions in the Suguta Valley, northern Kenya, during the Early-Middle Pleistocene Transition

Abstract

The Early-Middle Pleistocene Transition (EMPT) between 1200 and 700 ka represents a major global climate transition from dominantly 41,000- to 100,000-year glacial cycles. The forces and mechanisms behind this transition and the response of African environments are not well understood. The active volcanism and tectonics of the East African Rift System add complexity to local environmental systems and can erase important proxy records, inhibiting studies of lacustrine dynamics. As a result, there is minimal understanding of how this transition impacted the region's lake systems. At Paleolake Suguta, in the northern Kenya Rift, however, flood basalts cap lacustrine EMPT-age deposits, preserving these strata and their valuable paleoenvironmental record. This research presents a high-resolution reconstruction of hydrological change from approximately 931 to 831 ka within the Suguta-Turkana Basin in the northern Kenya Rift. Paleolake dynamics are reconstructed from a 41 m sedimentary section using diatom morphology, sedimentology, and X-Ray Fluorescence elemental analysis. Results show that lake levels varied greatly during this part of the EMPT with two wetter phases and two drier phases developing over about 100 kyr. From ∼885–831 ka, especially, the Suguta-Turkana Basin exhibits rapid changes in paleohydrology, ranging between deep stratified lakes; shallow, well-mixed lakes; and complete desiccation, with some of these changes occurring on an order of hundreds of years. This EMPT Suguta-Turkana-Baringo record therefore provides valuable insight into hydroclimate variability at an overall resolution of several thousand years, allowing reconstruction of past environments during a period of poorly understood terrestrial environmental change.