Climate-driven lacustrine dynamics from the Early Pleistocene Lorenyang Lake, Turkana Basin, Kenya
Résumé
Two stratigraphic records from Kaitio in West Turkana, Kenya, span 1.87 - 1.34 Ma, and document environmental
character and variability through a critical interval for human evolution and cultural development. The WTK13
core collected by the Hominin Sites and Paleolakes Drilling Project (HSPDP) recovered 216 m of sediment at
95% recovery. A parallel outcrop record of 180 m was investigated in exposures along the Kaitio laga close to the
drill site. Six tephrostratigraphic markers, the Chari, Lokapetamoi, 22Q-3, Etirr, Ebei and KBS Tuffs are present
in the outcrop and/or core. These were characterized by single-shard geochemical analysis, and provide links to
the well-established tephrochronology of the Turkana Basin. Magnetic polarity stratigraphy of the two records
documents the top of the Olduvai Subchron (C2N) at 1.78 Ma.
The lithostratigraphic record, bolstered by magnetic susceptibility and sedimentary facies characterization, demonstrates
a first-order transition from a deeper lacustrine system to a dynamic lake margin setting, followed by delta
progradation. Facies analysis reveals repeated fluctuations of lake level at Milankovitch and sub-Milankovitch
scales. Core-outcrop correlation allows detailed comparisons between diagenetically-prone outcrop samples and
more pristine samples from the deep core. The excellent preservation of the core sediments makes it possible to
obtain critical climate records of organic biomarkers, pollen, phytoliths and other proxies.
This detailed archive of environmental variability is closely linked to the rich paleontological and archaeological
discoveries from nearby sites and around the Turkana Basin