Intra- and inter-tooth variation in strontium isotope ratios from prehistoric seals by laser ablation multi-collector inductively coupled plasma mass spectrometry

RATIONALE

Strontium isotope ratios (⁸⁷ Sr/⁸⁶ Sr) in modern-day marine environments are considered to be homogeneous (~0.7092). However, in the Baltic Sea, the Sr ratios are controlled by mixing seawater and continental drainage from major rivers discharging into the Baltic. This pilot study explores if variations in Sr can be detected in marine mammals from archaeological sites in the Baltic Sea.

METHODS

⁸⁷ Sr/⁸⁶ Sr ratios were measured in tooth enamel from three seal species by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The method enables micro-sampling of solid materials. This is the first time that the method has been applied to marine samples from archaeological collections.

RESULTS

The analyses showed inter-tooth ⁸⁷ Sr/⁸⁶ Sr variation suggesting that different ratios can be detected in different regions of the Baltic Sea. Furthermore, the intra-tooth variation suggests possible different geographic origin or seasonal movement of seals within different regions in the Baltic Sea through their lifetime.

CONCLUSIONS

The method was successfully applied to archaeological marine samples showing that: (1) the ⁸⁷ Sr/⁸⁶ Sr ratio in marine environments is not uniform, (2) ⁸⁷ Sr/⁸⁶ Sr differences might reflect differences in ecology and life history of different seal species, and (3) archaeological mobility studies based on ⁸⁷ Sr/⁸⁶ Sr ratios in humans should therefore be evaluated together with diet reconstruction.

Polarization measurements in high-energy deuteron photodisintegration

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.