Paired 14C and 230Th/U burial ages of OES agree at ∼31 ka for an older LSA locality, validating the newer method, and in turn supporting its application to stratigraphically underlying MSA occurrences previously constrained only by a maximum 40Ar/ 39Ar age. Associated fauna, flora, and Homo sapiens fossils are thereby now fixed between 106 ± 20 ka and 96.4 ± 1.6 ka (all errors 2σ). Additional 40Ar/ 39 results on an underlying tuff refine its age to 158.1 ± 11.0 ka, providing a more precise minimum age for MSA lithic artifacts, fauna, and H. These results demonstrate how chronological control can be obtained in tectonically active and stratigraphically complex settings to precisely calibrate crucial evidence of technological, environmental, and evolutionary changes during the African Middle and Late Pleistocene. Understanding the complex and dynamic erosional/depositional interfaces that operated here during the Pleistocene was key to the Halibee chronological framework presented below. Fluvial deposition and erosion through time was largely controlled by the base level of downstream depocenters as the northward-flowing axial Awash River was tectonically dropped and/or volcanically dammed by the ongoing extension-related tectono-volcanic activity of the Afar Rift.
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