Stable isotope of Mesolithic remains of Pila wernei of the Nile area, Sudan: A tool for palaeoenvironment reconstruction

The article deals with stable isotopes of oxygen and carbon on current and archaeological semi-aquatic gastropod shell of the Pila wernei from Sudan and reports some new ¹⁴C analyses on archaeological Pila specimens. This, with the aim of obtaining new information on climatic and environmental changes in the al-Khiday area during the first phase of Holocene. The Pila shells come from a well-preserved shell midden present at al-Khiday and dated 8700-7000 cal yr BP. The area of al-Khiday was inhabited since at least 10 ka. Pila wernei species has never been studied in detail; this study demonstrates that the O and C isotope composition of aragonite shell is able to record the environmental and diet changes during the gastropod life. The comparison between the isotope data obtained on present-day and archaeological shells show a prevalence of C4 plants and higher rainfall during the Mesolithic. Two climatic fluctuations have been recognised: the first one indicating wetter conditions from 8650-8400 to 8500-8050 cal yr BP (decrease of the δ¹⁸O values), the second one pointing less wetter conditions from 8500-8050 to 7850-7600 cal yr BP (increase of δ¹⁸O values). Despite the difficulties in studying semi-aquatic gastropods due to their lifestyle habit, the identification of climatic fluctuations in the Early Holocene confirms the reliability of this proxy for climatic reconstructions. Despite the high number of isotopic analyses (1556) used in this work, they were not sufficient to mirror the fast climate changes characterising the studied period and finally obtain a detailed reconstruction for nearly the two millennia considered. Nonetheless, future projects may benefit greatly from unveiling the shell-environment relationship of the species.