Handaxes are the most representative artefacts of the Acheulean (Mode II) technology. Many handaxe-bearing Paleolithic sites were discovered along the Hanjiang River Valley (HRV) in the southern Qinling Mountain, whereas reliable ages of handaxes are relatively scarce due to a lack of primary stratigraphic dated context. The Longwanling (LWL) site is an open-air Paleolithic site located on the third terrace of the Hanjiang River. In 2021, four in situ handaxes with elaborate processing were unearthed from the first locality of the site. And a single-grain post-infrared infrared stimulated (pIRIR) luminescence dating method of potassium feldspar (K-feldspar) grains was applied to determine the age of the cultural layer for these handaxes. The equivalent dose of two samples showed obviously younger components, and their central age model (CAM) ages displayed reversal. We attribute this to post-depositional disturbance, which may result from the filling of cracks, e.g., by precipitation-induced slope flow. After excluding the disturbance of younger component with finite mixture model (FMM), a consistent chronological framework could be built, suggesting that the LWL handaxes were buried at ~134–110 ka, which corresponds to the oxygen isotope stage 5 (MIS5) with a relatively warm and humid climate. The age estimate is located within the chronological framework of the Acheulean technology in the Qinling Mountains Range. Our findings demonstrated that the combination of single-grain techniques and relevant statistical models can provide reliable age constraint for archaeological sites with complex depositional contexts.

Single-grain dating; Optically stimulated luminescence; Longwanling site; Handaxe; Hanjiang River Valley