High-resolution OSL dating of a late Quaternary sequence from Xingkai Lake (NE Asia): Chronological challenge of the “MIS 3a Mega-paleolake” hypothesis in China

- We conducted a combined OSL and 14C dating for a late Quaternary lake sequence.
- The reliability and robustness of OSL dates are confirmed.
- 14C dating may significantly underestimate age of sediments of beyond 30 cal ka BP.
- This paper challenges the 14C-based “MIS 3a Mega-paleolake” hypothesis in China.
- Sedimentation rate of Xingkai Lake related to global climatic changes on orbital timescales.

In this paper a combined OSL (49 samples) and 14C (14 samples) dating study was conducted on a sediment core from Xingkai Lake, NE Asia. A single-aliquot regenerative-dose protocol was used to determine the equivalent dose (De) of the extracted fine-grained (FG) quartz fraction; the suitability of the measurement procedure was confirmed by a set of luminescence tests (e.g., preheat plateau and dose recovery measurements). In addition, a post-IR infrared stimulated luminescence protocol at 290 °C (pIRIR290) was applied to the polymineral FG fraction of seven samples. Our results can be summarized as follows: (1) The uppermost sample was dated to ∼110 a, indicating that the OSL signal of FG quartz has been well bleached. This has been further confirmed by the consistency of OSL ages and pIRIR290 ages within <80 ka. The resulting OSL ages generally increased with depth, and the lowermost samples of core XK08 reached back to the last interglacial, although the pIRIR290 dating suggested that the quartz OSL ages likely begin to be underestimated beyond 80 ka; (2) The comparison of OSL and 14C ages suggested that the radiocarbon dating technique may significantly underestimate the age of sediments for samples older than 30 cal ka BP (corresponding to ∼25 14C ka BP), and thus it is necessary to pay attention when using such old 14C dates for paleoclimatic/archaeological interpretation; (3) This study challenges the radiocarbon-based chronology of the “MIS 3a Mega-paleolake” hypothesis, which had been reiterated for many years and extensively reported across northern and western China; and (4) The current high-resolution OSL dating record (one-age/5-10 cm) showed clear sedimentation rate changes down the core. The identified variations in the sedimentation processes at the orbital timescale may be related to regional/global climatic changes during the past 130 ka, and the high sedimentation rate during the last ∼0.4 ka has probably been caused by intensified human activities in the Xingkai Lake catchment.