New ages for the Upper Palaeolithic site of Xibaimaying in the Nihewan Basin, northern China: implications for small-tool and microblade industries in north-east Asia during Marine Isotope Stages 2 and 3

It has been suggested that the 'small-tool' and microblade Upper Palaeolithic industries coexisted in the Nihewan Basin of northern China for about 8-14 000 years during Marine Isotope Stage (MIS) 2. This inference was based on uranium-series ages of around 15 and 18 ka for bovid teeth recovered from the 'latest' small-tool site of Xibaimaying - the youngest occurrence of such tools in the region - and optically stimulated luminescence (OSL) dating of the earliest typical microblade site (Youfang: ∼26-29 ka). In this study, we re-dated the Xibaimaying site using single-grain OSL methods and the resulting ages indicate that the cultural layer was deposited 46 ± 3 ka ago, during MIS 3 - more than 20 millennia earlier than previously thought and older also than the so-called earliest 'primitive' and typical microblade tools found at Zhiyu (∼31-39 ka cal BP) and Youfang. These new ages for human occupation of Xibaimaying remove support for the parallel development of the small-tool and microblade industries in the Nihewan Basin during the Upper Palaeolithic, but reliable age estimates from additional sites are needed to confidently infer the nature of the chronological relationship between these two Upper Palaeolithic industries and the associated toolmakers.