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Rationale Embedding resins are commonly used to facilitate high-resolution sampling for stable isotope analysis but anomalous δ13C values have been observed in some cases. Here we compare the results of microsampling strategies for hand-drilled versus resin-embedded micromilled samples from the same marine shells to assess whether resin contamination is implicated in δ13C spikes. The comparison allows assessment of the relative benefits for spatial resolution, seasonal range for both δ18O and δ13C, and sample failure rates. Methods Hand-drilled samples were obtained from two bivalve shells (Spisula sachalinensis), corresponding to micromilled samples on the same shells where high δ13C spikes were observed. All carbonate powders were analysed using a dual-inlet Isoprime mass spectrometer and Multiprep device. Results from both sample sets were compared statistically. Results No anomalous high δ13C values and no failures due to insufficient gas were observed in the hand-drilled samples in contrast to the embedded micromilled sequences. Spatial resolution was reduced (~2.5×) in the former compared with the latter, resulting in a small reduction in the total range observed in the micromilled δ13C and δ18O values. Reduced sampling resolution between the two datasets was only significant for δ18O. Conclusions For S. sachalinensis (as with other similar bivalves), rapid growth mitigates the reduced sampling resolution of hand drilling and does not significantly impact observed isotopic range and seasonal patterning. Occurrence of anomalous δ13C values were eliminated and failure rates due to insufficient sample size greatly reduced in the hand-drilled dataset. We can find no other explanation for the occurrence of δ13C spikes than contamination by the embedding agent. We conclude that the logistical and interpretational benefits of careful hand drilling may be preferable to resin embedding for micromilling in marine shells, corals or speleothems where growth rate is rapid and the highest resolution is not required.

This paper presents a four year subannual isotope marine temperature record using modern Spisula sachalinensis specimens from Tomakomai (Hokkaido's Pacific coast, Japan). This species is commonly found in pre- and protohistoric shell middens and faunal assemblages from around the Seas of Japan and Okhotsk, so has significant potential as an indicator of past marine and, by inference, climatic conditions. However, previous sclerochronological research on the species’ growth has shown significant geographical variation in growth pattern, rendering palaeoclimatic interpretation difficult. To address this issue, this study applied sequential isotopic analysis to two sectioned modern valves, providing a proxy for sea surface temperature (SST) and allowing the direct identification of seasonality during shell growth. The sequences span four years of growth, as confirmed by visually identified growth patterns and the oxygen stable isotope results, which show clear annual cycles in δ18O. δ13C seasonality is less clear, but shows a weak inverse correlation with temperature potentially relating to primary productivity. Annual growth lines show that shell growth occurs during both warmer and cooler SSTs, but is more rapid during the cooler seasons. This is consistent with warm-season growth minima seen in shells from Hakodate Bay by Kato and Hamai (1975), but not with their suggestion that it is associated with shells growing at the southern limits of their distribution. Comparison to average local SST shows that δ18O-derived temperature falls within the expected range, but, contrary to expectations given preferential cool-season shell growth, appears biased towards warmer temperatures. Factors that could contribute to this are discussed. Overall, stable isotope analysis of Spisula sachalinensis is considered a useful complement to macro/microscopic sclerochronological research in building a holistic picture of shell growth, and has significant potential as a high resolution proxy for palaeoenvironmental studies of past SST.

Mitoc-Malu Galben (Romania) is one of the key-sites for the Upper Palaeolithic in Eastern Europe, with abundant Upper Palaeolithic archaeological layers embedded in a similar to 14 meters long loess-palaeosol sequence. The excavations in 1978-1990 yielded rich remains of Aurignacian and Gravettian workshops. From 1992 to 1995, an international collaboration helped better define their stratigraphical position, age, and typological characteristics. Since 2013, our team has conducted new fieldwork focusing on interdisciplinary study of site formation processes and a detailed technological study of the lithic artefacts. These different excavation phases have employed quite substantially different fieldwork methodologies. Here, we explore the impact of the changing excavation methodologies on the comparability of the generated assemblages by analyzing the frequency of bladelets among the elongated blanks as well as the length distribution of elongated blanks. Our preliminary study allows us to suggest that some of the assemblages seem to be influenced by the fieldwork methodology employed by each excavation phase, but more studies are needed to start to understand how the assemblages are biased. info:eu-repo/semantics/publishedVersion