Great attention was paid in the excavation to stratigraphic control. Excavated areas were divided into subareas (1 m by 1 m, Extended Data Fig. 1b), and deposits were removed in 10–20 cm spits within stratigraphic units. Three-dimensional spatial information was recorded for all artefacts and animal remains with the ATK system and ‘Agisoft Photoscan’ program (Extended Data Fig. 1c), and systematic geological sampling was conducted for sedimentological analysis and palaeoenvironmental reconstructions. Wooden relics (including wooden implements) were kept in place and labelled. After taking photos and measurements, wooden relics were wrapped in plastic and stored in purified water. Carbowax (Polyethylene glycol [PEG]) was used as a bulking and consolidating agent for later treatment.
Extensive sieving and flotation were carried out on the site. All the excavated sediments in the cultural layers were marked with the origin of layer and subarea and wet-sieved on the site. These sediments were soaked, stirred and precipitated with water, then filtered through a 0.25 mm sieve to separate macroscopic plant remains. The sediments were then passed through a 0.5 cm mesh to separate out clasts (including stone artefacts), fossils and other remains. 25 litres of these sediment samples were randomly selected from each subarea for sieving through a 0.25 mm mesh to retrieve small mammal fossils. Drone aerial photography was used to show the location of the excavation and the topography surrounding the site (Fig 2a).
The magnetic polarity of the section was established by collecting 29 orientated bulk samples from T3 at 10–20 cm intervals along the sequences from the GTQ site and underlying terrace. The bulk samples collected were each cut into 20×20×20 mm cubes for palaeomagnetic measurements. All specimens were firstly subjected to subjected to 80 °C and 150 °C thermal demagnetization followed by alternating field demagnetization at peak fields up to 60 mT at 5–10 mT intervals, and then were subjected to stepwise thermal demagnetization up to 610 °C with 13 steps and 10~50 °C temperature increments using the TD-4 thermal demagnetizer. The remanence measurements were made using a 2G-760-R cryogenic magnetometer installed in a magnetically shielded space with a background field of <300 nT. All the experiments were performed in the Palaeomagnetism and Geochronology Laboratory of the Institute of Geology and Geophysics, Chinese Academy of Sciences. Demagnetization results were evaluated by orthogonal diagrams22, and the principal component direction was computed by means of principal component analysis23 on a minimum of four consecutive steps using the PaleoMag software24. All the samples showed a normal polarity. Based on the biostratigraphy and the OSL and ESR dates (see below) which suggest a late Middle-Pleistocene age for the site, we correlate this magnetozone with the Brunhes Chron of normal polarity, indicating that the age of the excavated deposits is <780 kyr.
Electron Spin Resonance/U-series Dating
Three fragments from a mammalian tooth (GTQ-T4-F12, Supplementary Fig. 7) from the Layer 8 of T4, were analysed using electron spin resonance (ESR) method. Dentine and sediment attached on each side of the enamel tissue (sediment-enamel-dentine geometry) were removed carefully by dental drill. The average thickness of enamel fragment before and after the surface grinding were measured. Over 20 μm of the dentine and sediment sides were removed to eliminate alpha dose contribution. Then the enamel samples were crushed and ground into 100-200 μm powder and divided into 10 aliquots for gamma irradiation. Irradiation were pursued at Pekin University with a calibrated 60Co source and the irradiation doses are 10.7, 19.9, 39.1, 76.7, 148.6, 292.2, 592.3, 1019.0, 1318.0, 1843.0, 2678.0, 4522.0 Gy, respectively. The irradiated enamel aliquots were stored for one month before measurement to eliminate unstable signal in the samples.
The ESR measurement were carried out on a X-band Bruker ER041XG ESR spectrometer at the Institute of Geology, China Earthquake Administration. ESR measurement was performed at the room temperature with the acquisition parameters below: 1mW microwave power, 100 kHz modulation frequency, 0.1 mT modulation amplitude, 5 ms time constant, 20 ms conversion time, 1024 points resolution and 5 scans for each measurement. ESR signal intensity of enamel was extracted from T1-B2 peak-to-peak amplitude and normalized by the weight of aliquot. Each sample was measured four times for checking reproducibility. A single saturation exponential (SSE) function was used to fit the dose response data points to determine the De of the enamel sample (Supplementary Fig. 7). The De is calculated by extrapolating the dose response curve on to the x-axis, which yields a value of 256 ± 5 Gy.
The uranium-series isotopes in the dental tissues were analysed using a Nu Plasma multi-collector inductively coupled mass spectrometer (MC-ICP-MS) at the Radiogenic Isotope Facility (The University of Queensland). The measured uranium concentration in the enamel and dentine tissue were extremely low (~ 0.02 and ~ 0.1 ppm respectively) (Supplementary Table 7), indicating a weak uranium mobility in the groundwater caused by reduction of soluble U(+VI) to insoluble U (+IV) and followed by precipitation in an anaerobic (reductive) environment. This explains why the wooden tools at GTQ could be well preserved. The corrected U-Th ages of both tissues were 128.5 ± 6.8 kyr and 37.9 ± 2.7 kyr. Since no obvious uranium loss in both tissues was indicated by the 230Th/234U ratio, the U-Th ages are considered as the minimum constraint of the fossil age.
The coupled ESR and U-series age of the fossil sample were calculated by US-ESR model with “DATA” program 25. This model introduces a U-uptake parameter p to describe the uranium uptake history in each dental tissue 26. For the external dose rate, since the uranium concentration in the dental tissues of fossil sample are extremely low, the beta dose contribution from the dentine is negligible and, hence, only the external dose rate (including beta, gamma and cosmic ray dose rates) from the sediment side was taken into account. Since the sediments attached to the fossil had been removed during excavation, we estimated the sediment dose rate based on the average beta and gamma dose rates obtained from two of the optical samples (GTQ-T4-6 and GTQ-T4-7), both were taken from a depth (1.75 m and 1.9 m, respectively) similar to that of the fossil sample (Supplementary Table 4).
The following parameters were used for dose rate and ESR age calculation of the fossil samples: alpha efficiency 0.13 ± 0.02 27; beta attenuation factors were based on Marsh 28; dose rate conversion factors from Adamiec and Aitken29; water content in the dentine and enamel tissues are estimated 5 ± 2% and 0 respectively. No radon loss in the dental tissues were assumed. The early-uptake (EU) and linear-uptake (LU) model ages 30 were calculated to test the model sensitivity of combined ESR/U-series age estimates. A combined U-series-ESR (US-ESR) uptake model 26 and a closed-system U-series ESR model (CSUS-ESR)31 were also calculated; the latter would give a maximum constraint of the fossil ESR age. The dose rate data and age estimates obtained using different models are summarised in Supplementary Tables 8 and 9. Given the low concentration of U in the fossil, different U-uptake models yielded indistinguishable age estimates at ~288 ka, which is excellently consistent with the four optical ages (from ~240 to ~320 ka) obtained for the sediment from the same layer.
The age of the wooden artefacts was constrained by optical dating 32 of the artefact-bearing sediments. Sediment samples were collected by using stainless steel tubes hammered horizontally into cleaned stratigraphic sections. Sample preparation followed standard procedures as described in previous studies 33. Potassium-rich feldspar (K-feldspar) grains ranging in size between 90 and 212 μm in diameter were extracted. The separated grains were etched in 10% hydrofluoric acid to remove the alpha-irradiated surface layer. The time of sediment deposition is estimated by dividing the equivalent dose (De, i.e., the radiation energy absorbed by grains since deposition) by the environmental dose rate (the radiation dose received by the grains per unit of time) 32,34. For De determination, the infrared (IR) stimulated luminescence (IRSL) of K-feldspar grains was measured. De values for individual K-feldspar grains were determined using a two-step (200 °C and 275 °C) regenerative-dose post-IR IRSL (pIRIR) procedure 33,35,36 and the recently developed standardized growth curve and LnTn approaches 37-41 (details are provided in the Supplementary Information Section 2).
The environmental dose rate for K-feldspar grains includes contributions from beta particles, gamma rays, cosmic rays. The external beta dose rate was estimated from beta-counting of dried and powdered sediment samples using a Risø low-level beta multicounter system. The gamma dose rate was measured by in situ gamma spectrometry at each sample location. The cosmic-ray dose rate was calculated by taking account of the latitude, longitude and altitude of the site and the burial depth of each sample40. The total dose rate of the K-feldspar grains also includes an estimate of the internal beta dose rate due to the radioactive decay of 40K and 87Rb within the grains. A K concentration of 12 ± 1% and a Rb concentration of 400 ± 100 ppm are assumed 42,43. The measured beta dose rates were corrected for grain-size attenuation, and the beta, gamma and cosmic-ray dose rates were adjusted for water content (based on the measured field values). Details of sample preparation, De determination methods, and environmental dose rate determination are given in the Supplementary Information Section 2.
Code availability. All custom R code used to produce the dating results presented here are available from the corresponding authors on reasonable request.
Reporting summary. Further information on research design is available in the Nature Research Reporting Summary linked to this paper.
All data generated and/or analysed during the current study are available from the corresponding authors on reasonable request.
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