Single-grain K-feldspar pIRIR dating of the Longwanling handaxe-bearing site in the Hanjiang river valley, central China

Abstract

Many handaxe-bearing Early Paleolithic sites were discovered in the Hanjiang River Valley in the southern Qinling Mountain Range. However, reliable radiometric ages are relatively scarce due to the paucity of primary stratigraphic dated sequences. The Longwanling (LWL) site is an open-air Paleolithic site located on the third terrace of the Hanjiang River Valley (HRV), where five handaxes were unearthed in 2021 in situ at Locality-1. Here, both single-grain and single-aliquot post-infrared infrared stimulated luminescence dating methods of potassium feldspar grains were applied to determine the age of the cultural layer for these handaxes. The equivalent dose of samples NJU4051 and 4052 showed clear younger components. The single-grain ages obtained through the central age model and single-aliquot ages of these two samples are much younger than three other samples which show age reversal. We attribute this reversal to post-depositional disturbance, which may result from the filling of cracks, e.g., by precipitation-induced surface runoff. After excluding the disturbance of the younger component using a finite mixture model, a consistent chronological framework could be built, suggesting that the LWL handaxes were buried at ∼140–110 ka, which corresponds to Marine Isotope Stage 6 and 5. Our findings demonstrate that the combination of single-grain techniques and relevant statistical models can provide a reliable age constraint for archaeological sites with complex depositional contexts. In addition, the chronological framework of Chinese handaxes is mainly concentrated in the time intervals of ∼0.8 Ma and ∼210–50 ka (the LWL site falls within the latter range).