Multiple luminescence dating on heated materials at the nanzuo archaeological site, central Chinese Loess Plateau

Abstract

Nanzuo is a key Neolithic archaeological site in the central Chinese Loess Plateau (CCLP). The site is important for understanding the origin and development of the Chinese civilization, yet, it lacks a robust chronological framework. The current work, for the first time, dates two different types of heated materials (pottery and burnt soil) from a profile near the main excavation of the Nanzuo archaeological site using various luminescence dating techniques. These techniques included single grain (SG) quartz OSL and K-feldspar post-infrared infrared-stimulated (pIRIR) dating for burnt soil samples and pottery, and pIRIR dating for pottery slices using the rock surface luminescence technique (RSL). The reliability of luminescence dating was investigated by comparing SG quartz, K-feldspar and pottery slice ages with radiocarbon (¹⁴C) ages obtained from the same cultural layer. The results show that the SG quartz OSL and K-feldspar pIRIR₂₂₅ age estimates of the two coarse potteries are consistent with the ¹⁴C ages, however, the age estimates of the pottery slice (NZ22-CPS150) are significantly younger, which is primarily explained by underestimation in equivalent doses (D_e). Moreover, it is noted that while there is a considerable variation in the D_e of coarse pottery slices with depth, no significant correlation is observed between K- content and D_e. Heterogeneous K content was revealed by μ-XRF scanning on coarse pottery slices. Conversely, fine pottery displayed homogeneous K-content distribution and age estimates consistent with the ¹⁴C ages. Thus fine pottery slices are suggested to be more suitable for pIRIR dating relative to coarse pottery slices. The underestimation of D_e values in mixed minerals is observed as the primary reason for underestimated slice ages compared to SG K-feldspar, with grain size of K-feldspar and K content variation playing only a minor role. Therefore, by integrating the ¹⁴C ages with the luminescence ages of the pottery, it is inferred that human occupation of the Nanzuo site occurred around 5100 to 4500 years ago, which aligns with the ¹⁴C ages obtained from the main section of the Nanzuo site. The current work further concludes that the single-grain luminescence dating method is reliable for pottery. The study recommends to prioritize materials characterized by relatively uniform potassium (K) content for pIRIR dating using pottery slices.