pIRIR and IR-RF dating of archaeological deposits at Badahlin and Gu Myaung Caves – First luminescence ages for Myanmar

Abstract

Reliable chronologies are essential for understanding the timing and routes of human dispersal through Southeast Asia, both of which remain open questions. This study provides luminescence chronologies for two archaeological sites in Myanmar-Badahlin Cave and Gu Myaung Cave-from which Palaeolithic artefacts have been recovered. We applied single-grain post-infrared infrared stimulated luminescence (pIRIR) and multi-grain infrared-radiofluorescence (IR-RF) dating methods to potassium-rich feldspar (Kfeldspar) grains extracted from the sedimentary deposits at these two sites. Luminescence characteristics of the K-feldspar extracts showed that the procedures were well suited for dating. The single-grain pIRIR ages suggest human occupation of Badahlin and Gu Myaung Caves by ~30 ka and ~25 ka, respectively, although the age estimates for Gu Myaung Cave are much older than the radiocarbon ages. The ages obtained using the IR-RF signal are even older, which we attribute to insufficient bleaching of this signal-and perhaps also the pIRIR signal-and the probable existence of a substantial residual dose at the time of sediment deposition.

Re-evaluating Pleistocene–Holocene occupation of cave sites in north-west Thailand: new radiocarbon and luminescence dating

“…Radiocarbon-and luminescence-based chronologies from Tham Lod and Ban Rai rockshelters suggested forager occupations extending into the Late Pleistoceneover 30 000 years ago at Tham Lod-but only a sporadic Holocene occupation. More recent analyses show a similar trend: luminescence ages from Badahlin Cave in Myanmar indicate human occupation in the Pleistocene, and radiocarbon measurements from Doi Pha Kan in Thailand date to the Terminal Pleistocene (Imdirakphol et al 2017;Schaarschmidt et al 2019). Evidence for Holocene foragers in north-west Thailand is less well-established.…”

Infrared radiofluorescence (IR-RF) dating: A review

“…3). Varma et al (2013) reported that although the IR-RF signal of their sample was almost at its saturation level, it did not show significant phosphorescence after bleaching the sample for 800 s. Hence, they concluded that no extra pause is needed and suggested that a delay of 500 s is sufficient to reduce the phosphorescence down to the background level if the bleaching time is less than 800 s. Similarly, Schaarschmidt et al (2019) reported a weak phosphorescence compared to the IR-RF signal and reduced the pause to 900 s for their samples.…”

“…In summary, it seems that phosphorescence caused by bleaching can be avoided by introducing a pause of 15 min to 1 h prior to IR-RF measurements (Erfurt and Krbetschek, 2003b;Frouin et al, 2015;Schaarschmidt et al, 2019) in the case of solar simulator bleaching and may not be required if the sample is bleached with a UV LED for 800 s or longer (Varma et al, 2013).…”

Review of the Post-IR IRSL Dating Protocols of K-Feldspar

“…Different methods were applied to overcome the fading problem, such as the fadia method [119][120][121], the isochron method [122], isolating 'zero'-fading grains [123], and fading correction [124,125]. After the pIRIR dating protocol was established, single-grain pIRIR dating with K-feldspar has been reported in numerous studies [43,108,[126][127][128][129][130][131][132][133][134][135][136][137]. The machine time can be saved by performing prior-IR stimulations on all the grains simultaneously [108,129,137].…”