Relative paleointensity correction of radiocarbon reservoir effect for lacustrine sediments on the northeast Tibetan Plateau

Abstract

An accurate chronological framework is vital if we are to use lacustrine sediments on the Tibetan Plateau (TP) for paleoclimate reconstruction. Radiocarbon (14C) dating is the most frequently used method for dating late Quaternary lacustrine sediments. However, it is often affected by potential reservoir effects. Owing to the complex hydrogeology and sedimentology processes of the lake we study in this paper, it is difficult to correct this effect. Geomagnetic relative paleointensity (RPI) method has demonstrated the potential to construct an accurate high-resolution chronological framework for sediments in the Brunhes chron. In this study, we present an RPI record as well as environmental magnetism results from a core (HL) on the Hurleg Lake in the northeast TP. We aim to determine the reservoir effect and establish an accurate timescale for the core. The RPI record was constructed by normalizing the natural remanent magnetization after 30 mT alternating field demagnetization with saturation isothermal remanent magnetization (NRM30mT/SIRM). This exhibits a general agreement with other geomagnetic intensity stacks from the world, suggesting that global-scale patterns of geomagnetic paleointensity behavior were also documented in Hurleg Lake sediments. Our RPI record can be adequately matched to RPI references to provide three additional age tie points for the HL core. We then evaluated the reservoir effect and constructed a timescale for the core using chronological controls from both RPI and 14C dating. The estimated RE age was weak below 272 cm, was 2–3 ka at the upper 50 cm, and was inferred to have increased between depths of 272 and 50 cm. Environmental magnetism sequences from core HL display a similar paleoclimatic pattern with records from core HL05-2 and core K-2 both in the Hurleg Lake area, suggesting that correction for the radiocarbon reservoir effect is accurate and timescale of core HL is reliable. Our study further demonstrates that the method of obtaining age control points from RPI is applicable to lake sediments on the TP.