Dating of ancient ceramics from Churajon archaeological site, Arequipa, Peru by Tl technique

The ceramic fragments from the archaeological site of Churajon [Jofrey et al, 2020], Arequipa, Peru, were dated by thermoluminescence (Tl) technique. For this purpose, the outer layer of the ceramic fragments was removed to eliminate any unknown external effects and the obtained cores were carefully crushed in a hydraulic press and sieved to retain grain sizes between 0.150 and 0.250 mm in diameter. All the crushed material was subjected to an H₂O₂ solution to remove organic material and to 10% HCl to dissolve the carbonate minerals and metal oxides. Then, a 20% HF solution is used to corrode the surface of the grains and eliminate the pre-effects of α-rays. The quartz grains obtained after the chemical treatments were sieved again to obtain grains of size between 0.150 and 0.250 mm in diameter for the thermoluminescence measurements [Joseff et al,2020]. All sample preparation was carried out under subdued red light to prevent affecting the dating signal from quartz. The quartz grains obtained were irradiated from 10 Gy to 100 Gy gamma dose using a Co-60 source. For Tl measurements a Harshaw 3500 equipment was used. Before Tl measurements, all samples were heat-treated at 230 °C for 5 seconds to eliminate Tl peaks below 250°. Tl glow curves show a very intense peak at about 258 °C. The age of the samples was between 675 ± 83 years determined by the additive Tl technique. Our study, based on the Tl technique to study pottery from the Churajon archaeological site, will be of great help to archaeologists in Peru. With the results of this research, we can understand the chronology and determine the areas of dispersion and density of the archaeological occupation in the Arequipa Valley. (author)