17:15 〜 18:45
[MZZ44-P04] Influences of environmental factors in bioavailable Sr isotope ratios in archaeological cattle bones
キーワード：87Sr/86Sr isotope ratios, Isotope geoarchaeology, Marine Sr dispersion, Coastal environments
The isotope ratios of 87Sr/86Sr in animal bones reflect the Sr isotope ratios in their dietary components. In the case of domesticated herbivores, it is expected that their diet will closely reflect the local soil and groundwater ratios. However, studies have shown that the Sr isotopic ratios may differ from those of the local soil and grass, suggesting the influence of other components besides the local soil (Scott et al. 2020, Appl. Geochem). A recent study investigating the source of bioavailable Sr in archaeological cattle bones from coastal Bengal, India, revealed a strong contrast in Sr isotope ratios between bulk soil (0.72271) and cattle bones (0.71566) from the Chalcolithic to recent times, with minor variations observed within cattle bones over time (Dey et al., 2023, J. Radioanal. Nucl. Chem.). The authors speculated that the lower Sr isotope ratio in cattle bones was due to Sr derived from seawater, as the regional ground and surface water Sr isotope ratios were reported to be higher than the measured soil.
In this study, we examine the variability in Sr isotope ratios of water-soluble and insoluble fractions in the soil. Plants absorb Sr present in the soil along with water. Therefore, it is likely that the bioavailable strontium originates from the water-soluble portion of the soil. The water-soluble fraction from three soil samples, taken from the same layers as the cattle bones, was analysed. The data shows significantly lower 87Sr/86Sr isotopic values (ranging from 0.71606 to 0.71721), indicating that the bioavailable strontium is depleted in radiogenic 87Sr compared to the bulk soil. The lower ratio in the soluble fraction may have originated from marine-derived sea salt through the deposition of aerosol or rainwater. The results suggest that the 87Sr/86Sr ratio of bioavailable Sr may be significantly influenced by marine Sr in coastal areas, even at a distance of several tens of kilometres from the coastline.
In this study, we examine the variability in Sr isotope ratios of water-soluble and insoluble fractions in the soil. Plants absorb Sr present in the soil along with water. Therefore, it is likely that the bioavailable strontium originates from the water-soluble portion of the soil. The water-soluble fraction from three soil samples, taken from the same layers as the cattle bones, was analysed. The data shows significantly lower 87Sr/86Sr isotopic values (ranging from 0.71606 to 0.71721), indicating that the bioavailable strontium is depleted in radiogenic 87Sr compared to the bulk soil. The lower ratio in the soluble fraction may have originated from marine-derived sea salt through the deposition of aerosol or rainwater. The results suggest that the 87Sr/86Sr ratio of bioavailable Sr may be significantly influenced by marine Sr in coastal areas, even at a distance of several tens of kilometres from the coastline.