d13C values in archaeological 14C-AMS dated charcoals: assessing mid-Holocene climate fluctuations and human response from a high-resolution isotope record (Arslantepe, Turkey)

RATIONALE: Past climate has always influenced human adaptation to the environment. In order to reconstruct palaeoclimate fluctuations and their role in the evolution of Near Eastern societies during the mid-Holocene, high-resolution Δ13C records from fossil wood remains at the archaeological site of Arslantepe (eastern Turkey) have been developed. METHODS: After chemical treatment, 13C values were measured by sample combustion flow using a FLASH EA-CHNS instrument interfaced with a Delta V isotope ratio mass spectrometer via a CONFLO III. Two replicates per sample were analysed. The measurement precision was evaluated by propagating variations of the 13C values of samples and V-PDB standards, whereas the accuracy was checked by a quality control sample. To account for changes in atmospheric CO2, Δ13C values were calculated. In addition, 14C/12C ratios were measured by means of ann AMS system (3 MV tandem accelerator). RESULTS: Mean Δ13C curves of deciduous Quercus and Juniperus from archaeological levels between 4700 and 2000 BC (Arslantepe periods VIII-VI D) were produced, where the isotope values were ordered by the available RC ages. Interspecific variations of evergreen vs deciduous plants were postulated for the juniper Δ13C values being higher than 3‰. The seasonal rainfall amount was recorded by the juniper remains, while the water table levels were obtained from the oak samples. CONCLUSIONS: The local climate experienced times of enhanced/reduced precipitation in concert with regional trends. Anomalies in the air mass circulation from the Mediterranean basin also produced oscillations of rainfall amount. In such a frame the Rapid Climate Change dry events had a consistent signature in the Arslantepe Δ13C record, thus potentially contributing to social or organisational changes at the site