Freshwater Reservoir Offsets Investigated Through Paired Human-Faunal14C Dating and Stable Carbon and Nitrogen Isotope Analysis at Lake Baikal, Siberia

Abstract

Thirty-three paired accelerator mass spectrometry (AMS) radiocarbon dates on human and terrestrial faunal remains from the same Neolithic and Early Bronze Age graves are used to develop a correction for the freshwater reservoir effect (FRE) at Lake Baikal, Siberia. Excluding two outliers, stable nitrogen isotope (δ15N) values show a positive correlation(r2= 0.672,p< 0.000) with offsets in14C yr between paired human and fauna determinations. The highest offset observed in our data set is 622 yr, which is close to the value of ∼700 yr suggested for endemic seals in the lake. For each per mil increase in δ15N, the offset increases by 77 ± 10 yr in the overall data set. However, there are indications that different regression models apply in each of two microregions of Cis-Baikal. In the first, sites on the southwest shore of the lake and along the Angara River show a strong positive correlation between δ15N values and offsets in14C yr (r2= 0.814,p< 0.000). In the other, the Little Sea, both δ13C and δ15N values make significant contributions to the model (adjustedr2= 0.878; δ13Cp< 0.001; δ15Np< 0.000). This can be related to the complex13C ecology of the lake, which displays one of the widest ranges of δ13C values known for any natural ecosystem. The results will be important in terms of refining the culture-history of the region, as well as exploring the dynamic interactions of hunter-gatherer communities both synchronically and diachronically.