Optical dating of Upper Palaeolithic deposits in the Altai Mountains, Siberia

Denisovans, Neanderthals and modern humans are hominin groups known to have occupied the Altai Mountains in the Late Pleistocence. The earliest Upper Palaeolithic (UP) in the Altai Mountains consists of two variants, the Initial Upper Palaeolithic (IUP) and Early Upper Palaeolithic (EUP). It is uncertain which of these hominin groups was responsible for the IUP and EUP. There are two models to explain the emergence of the UP in the Altai Mountains: the local transition model and the chrono-stratigraphic model. The former argues for the regional development of the local Levallois-Mousterian Middle Palaeolithic (MP) variant (LMV) into the IUP and EUP, while the latter argues for modern humans migrating into the region, bringing with them UP technologies. The former also considers the IUP and EUP to be contemporaneous, while the latter considers the IUP and EUP to occur in succession, with the EUP overlying to IUP. The IUP displays MP and UP elements, while the EUP represents a fully developed UP technology. Denisovans, Neanderthals and modern humans have all been suggested as makers of the UP. Optical dating, including optically stimulated luminescence (OSL) dating and postinfra- red infra-red stimulated luminescence (pIR-IRSL) dating, was conducted on UP stratigraphic sequences at four sites in the Altai Mountains: Denisova Cave, Anui-2, Anui-3 and Ust-Karakol-1 Trench 2. Fifteen final ages and nine preliminary ages were obtained for these four sites. These ages were then compared to the existing radiocarbon (14C), palaeomagnetic excursion, and radiothermoluminescence (RTL) ages. The ages produced in this project suggest that the IUP emerged around 62 ka, and the EUP emerged around 35 ka. This succession of the EUP overlying the IUP supports the chrono-cultural model. Further studies are required to determine if there was a hiatus between the LMV and the IUP and EUP, and to assign lithic assemblages to hominin groups based on reliable fossil associations.