Electron spin resonance dating of optically bleached quartz grains from the Middle Palaeolithic site of Cuesta de la Bajada (Spain) using the multiple centres approach

Abstract

Electron spin resonance (ESR) dating of optically bleached quartz grains was performed on three sediment samples collected from the Middle Palaeolithic site of Cuesta de la Bajada (Spain). A standard multiple grain and multiple aliquot additive dose procedure was employed, and both the Al and Ti centres were measured as part of the multiple centres approach. ESR age estimates obtained for the three samples indicate that the Al centre provides a maximum possible chronology; use of the Ti centres show that the Al signal was likely not systematically reset to its residual level during sediment transportation. A direct comparison between ESR ages based on the Ti centres and single grain optically stimulated luminescence (OSL) ages from samples collected nearby shows broadly consistent results. The Ti-H centre also appears to provide suitable chronologies for at least two of the three Middle Pleistocene samples studied here. Surprisingly, the only sample showing consistent ESR ages between the Al and Ti centres appears to be overestimated in comparison with the Ti-centre and OSL ages derived from the other two samples. This indicates either incomplete bleaching of both the Al and Ti centres for this sample, or unexpected impacts of other sources of D e uncertainty, such as multi-grain averaging effects. The ESR dating results overall indicate that the archaeological sequence of Cuesta de la Bajada CB-3 is most likely correlated to either MIS 7 or 9.

ESR and ESR/U-series chronology of the Middle Pleistocene site of Tourville-la-Rivière (Normandy, France) - A multi-laboratory approach

“…In contrast, the Ti-H centre provides age estimates that are in agreement with the ESR/U-series results. This demonstrates the great potential of this centre to date late Middle Pleistocene deposits, which is consistent with previous observations by Duval et al (2017). A multiple centre approach seems therefore indispensable when dating this type of fluvio-estuarine sediment, even when the sedimentological characteristics of the sediments seem initially quite suitable for an ESR study (as it was the case for the Tourville D1 and I units).…”

“…Previous cross-comparison studies showed good agreement with results derived from other numerical dating methods such as Luminescence, U-series and 40 Ar (e.g. Duval et al, 2017;Méndez-Quintas et al, 2018;Pereira et al, 2018). Unfortunately, given the very limited number of laboratories and researchers specialized in the ESR dating applications mentioned above, inter-laboratory comparison studies remain very rare.…”

“…Ti-H ESR ages ( Figure 6). In accordance with the principles of the MC approach, this overestimation is most likely due to incomplete bleaching (Duval et al, 2017). The geological nature of the D2 sediment (silty clayey deposits) could indicate a turbid water deposit in a decantation environment such as floodplain or muddy supratidal area.…”

“…A few recent applications studies may provide a fair idea of the time range applicability achieved by the MC approach. Ti-H signal has proven to produce age estimates consistent with independent age control from about 300 ka to 40 ka (e.g., Duval et al, 2017;Kreutzer et al, 2018), while Ti-Li and Al centres may provide accurate age results between about 200 ka and 2 Ma (Beerten and Stesman, 2006;Mendez-Quintas et al, 2018;Sahnouni et al 2018;Voinchet et al, this issue). For a time period younger than about 40 ka, none of the Al and Ti centres seem to yield accurate age results (e.g., Mendez-Quintas et al, 2018), which indicate the difficulty to detect low dose estimates (<100 Gy) with these signals.…”

“…Incomplete bleaching would therefore lead to different burial dose estimates for these three ESR signals, with the Ti-H signal typically providing the smallest dose and the Al signal the biggest one. In this case, the first one would most likely be the closest estimate of the true burial dose absorbed by the sample, whereas the second one would provide a maximum possible estimate (see Duval et al, 2017). However, the systematic application of the MC approach is sometimes complicated by the weak ESR signal measured for the Ti-H centre (see Rixhon et al, 2017), which makes it complicated to obtain meaningful results.…”