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Abstract Basic assumptions of the single aliquot regenerative dose (SAR) protocol are tested using the violet stimulated luminescence (VSL) signal from quartz. The VSL signal is shown to be reduced to a sufficiently low background level between SAR steps, and the SAR protocol appears to adequately correct for sensitivity changes during measurement. The VSL SAR protocol can recover a large (405 Gy) laboratory beta dose within uncertainties, however the mean value for the dose recovery ratio is commonly 0.8 or less. This poor behaviour is echoed in the measurements of equivalent dose (D e) for a sample with an expected D e of ∼354 Gy, which underestimates D e by 50–70%. Further investigations are required to understand the mechanisms underlying these underestimations in VSL SAR D e values. Highlights • Compared two single aliquot regenerative dose protocols for VSL signal. • Protocols assessed to minimise recuperation and optimise signal depletion. • Partial success in dose recovery of ∼400 Gy using post-blue VSL signal. • VSL signal gives 50–79% underestimation of the expected D e. [ABSTRACT FROM AUTHOR]

When electron spin resonance (ESR) is applied to sedimentary quartz, dealing with the poor bleachability of the signals is particularly challenging. In this study, we used both the single-grain optically stimulated luminescence (OSL) and the single aliquot ESR dating of quartz from deep sand deposits preserving a Stone Age archaeological sequence to combine the advantages of the two methods: good bleaching behaviour and extended age range. Using the youngest samples at each sampling site we were able to calculate the mean ESR residual age from the difference between the OSL ages and the apparent ESR ages. Focusing mainly on the single aliquot regenerative dose (SAR) protocol here, we were able to calculate the mean ESR residual age for the Ti and Al centres, including the non-bleachable signal component for the latter. For the NP site, residual ages of 209 ± 13 ka and 695 ± 23 ka were calculated for the two centres, whereas for the ZS site 268 ± 39 ka and 742 ± 118 ka were determined. These residual ages are significant and cannot be neglected. Thus, the residual age was subtracted from the apparent ESR ages. The validity of the residual subtraction method was tested through a comparison of the oldest OSL age from each site with the residual subtracted ESR age. For both NP and ZS sites, the residual subtracted Ti and Al ages were consistent with the OSL age within 2-σ uncertainty, and therefore confirm the robustness of the subtraction method. Within the NP sequence, we were able to locate the end of the Early Stone Age at 590 ± 86 ka, and this provides a maximum age for the transition to the Middle Stone Age in this part of south-central Africa. [ABSTRACT FROM AUTHOR]

Despite eastern Africa being a key location in the emergence of Homo sapiens and their subsequent dispersal out of Africa, there is a paucity of long, well-dated climate records in the region to contextualize this history. To address this issue, we dated a ∼293 m long composite sediment core from Chew Bahir, south Ethiopia, using three independent chronometers (radiocarbon, 40Ar/39Ar, and optically stimulated luminescence) combined with geochemical correlation to a known-age tephra. The site is located in a climatically sensitive region, and is close to Omo Kibish, the earliest documented Homo sapiens fossil site in eastern Africa, and to the proposed dispersal routes for H. sapiens out of Africa. The 30 ages generated by the various techniques are internally consistent, stratigraphically coherent, and span the full range of the core depth. A Bayesian age-depth model developed using these ages results in a chronology that forms one of the longest independently dated, high-resolution lacustrine sediment records from eastern Africa. The chronology illustrates that any record of environmental change preserved in the composite sediment core from Chew Bahir would span the entire timescale of modern human evolution and dispersal, encompassing the time period of the transition from Acheulean to Middle Stone Age (MSA), and subsequently to Later Stone Age (LSA) technology, making the core well-placed to address questions regarding environmental change and hominin evolutionary adaptation. The benefits to such studies of direct dating and the use of multiple independent chronometers are discussed. • Four independent dating methods applied to ∼293 m lake core from southern Ethiopia. • Reveals 620 ka high-resolution sedimentary record near key fossil hominin sites. • Mean accumulation rate of 0.47 mm/a comparable to other African lacustrine sediments. • Accumulation rate fell to 0.1 mm/a during MIS 2, likely due to reduced sediment supply. • Use of multiple independent chronometers is a powerful approach in lake settings. [ABSTRACT FROM AUTHOR]