Micromilling vs hand drilling in stable isotope analyses of incremental carbonates: The potential for δ ¹³ C contamination by embedding resin

RationaleEmbedding 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.MethodsHand-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.ResultsNo 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.ConclusionsFor 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

Archaeological marine carbonates in northern Hokkaido, Japan: methodology, chronology and palaeothermometry

The site of Hamanaka 2, Rebun Island (Hokkaido), contains an archaeological record including well-preserved faunal remains, including clam shells and cod otoliths, from hunter-gatherer groups across the Epi-Jomon to Historical Ainu periods. As demonstrated by sclerochronologists worldwide, incremental stable isotope analysis of marine carbonates can provide an archaeologically-relevant and directly-datable proxy record of oceanic palaeotemperature, which is especially important for coastal sites such as Hamanaka 2. Despite this, marine carbonates from the site have not yet been used for this purpose, partly due to concerns over a variable regional marine reservoir effect. This, in combination with the possibility of ‘old’ shells being incorporated into younger stratigraphic units, means that any climatic information gained can be difficult to associate conclusively with the stratigraphic unit from which it was excavated. This thesis aims to address the methodological and interpretational obstacles relating to the archaeological use of this material at Hamanaka 2, and considers the local palaeotemperature record these materials can provide and their implications. The first paper examines the candidacy of the Sakhalin surf clam as a sub-annual temperature record, using stable isotope analysis of modern shells to compare carbonate-derived temperature estimates with observed water temperature. The results confirm that, as with most large, slow-growing marine bivalves, this species is a reliable recorder or water temperature, although seasonal extremes are likely to be dampened in the shell isotopic record. The second paper focuses on the complications arising from high resolution incremental sampling of marine carbonates, specifically the issue of contamination from embedding resin, and the relative merits of hand drilling versus micromilling. Comparison between two series of directly comparable samples shows that embedding may produce implausibly high δ13C values in the embedded, micromilled samples. This is interpreted as evidence of the contamination effect of resin on δ13C, whilst δ18O appears unaffected. The results indicate that hand drilling fast-growing species can provide a sub-annual palaeotemperature record comparable to micromilling, minimising sampling time and maximising sample size. The final paper addresses the main archaeological questions of the thesis. It assesses the palaeotemperature record of shells and otoliths from Hamanaka 2 over the Epi-Jomon-Final Okhotsk period in the context of new radiocarbon dates, which are paired with existing terrestrial dates. This allows calculation of new marine reservoir corrections, useful not only for this site but all others in the region which contain similar marine evidence. The integration of marine material into Bayesian chronological modelling at Hamanaka 2 constrains the timing of the Final Okhotsk period more tightly compared to previous models, showing a revised end date of 1107-958 cal BP. δ18O results show no clear temperature trend across the study period, although the single Early Okhotsk otolith sampled is consistent with the existing suggestion that this period saw a short-lived period of cooler temperatures. Overall, stable isotope analysis and radiocarbon dating combine to show the potential of marine carbonate material from Hamanaka 2 as a climatic and chronological record

The potential of marine bivalve Spisula sachalinensis as a marine temperature record

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

New fieldwork at Mitoc-Malu Galben (Romania): An overview of the 2013 to 2016 excavations

Mitoc-Malu Galben is a key sequence for the European Upper Palaeolithic with abundant Aurignacian and Gravettian layers embedded in a long loess-paleosol sequence of about 14 metres depth. Here we present an overview of our 2013 to 2016 fieldwork campaigns resulting in 22 excavated trenches. We present new data on archaeological occurrences corresponding to the late Aurignacian as defined by the 1978 to 1995 excavations at the site.European Commission FP7 Marie Curie program (NEMO-ADAP project, grant n° 322261) European Commission H2020 Marie Skłodowska-Curie program (EU-BEADS project, grant n° 656325

New fieldwork at Mitoc-Malu Galben (Romania): An overview of the 2013 to 2016 excavations

Mitoc-Malu Galben is a key sequence for the European Upper Palaeolithic with abundant Aurignacian and Gravettian layers embedded in a long loess-paleosol sequence of about 14 metres depth. Here we present an overview of our 2013 to 2016 fieldwork campaigns resulting in 22 excavated trenches. We present new data on archaeological occurrences corresponding to the late Aurignacian as defined by the 1978 to 1995 excavations at the site

Quarante ans de recherches avec Vasile Chirica : Mitoc-Malu Galben

Reconnue comme gisement préhistorique depuis la fin du XIXème siècle, la station paléolithique de Mitoc–Malu Galben a attendu jusqu’en 1978 pour que son potentiel archéologique commence à être pleinement exploité. Vasile Chirica y entame à cette date des fouilles de grande ampleur, révélant une stratigraphie loessique complexe au sein de laquelle se succèdent occupations aurignaciennes et gravettiennes. Dès lors, les travaux de Vasile Chirica sur ce gisement exceptionnel permettront d’ouvrir son étude à la communauté scientifique. En collaboration avec d’autres chercheurs, le site fera l’objet de fouilles par une équipe internationale à partir des années 1990. Au fil du temps, toutes ces recherches ont permis d’établir Mitoc–Malu Galben comme l’une des séquences de référence du Paléolithique supérieur et de la transition Aurignacien- Gravettien à l’est des Carpathes. Dernièrement, quatre campagnes de fouille ont été conduites de 2013 à 2016. À travers diverses approches interdisciplinaires menées sur le site et le matériel extrait, les données les plus récentes permettent encore à l’heure actuelle de fournir de nouveaux éléments pour mieux appréhender ces deux paléocultures. Ce texte se propose de revenir brièvement sur ces résultats

The mid Upper Palaeolithic (Gravettian) sequence of Mitoc-Malu Galben (Romania): New fieldwork between 2013 and 2016 - Preliminary results and perspectives

This paper presents preliminary results of fieldwork conducted at the Upper Palaeolithic open-air site Mitoc-Malu Galben in northeastern Romania. The site has a ~14m deep loess-paleosol sequence with a rather high climatic resolution. The chronostratigraphy is well established and embedded in this long sequence are abundant archaeological remains, mostly attributed to the Aurignacian and Gravettian. Our fieldwork between 2013 and 2016 provided new samples of the main Aurignacian and Gravettian layers. Here we provide an overview of our fieldwork activities, the generated archaeological collections, and present a preliminary analysis of raw material economy and blank production and core exploitation strategies of the Gravettian assemblages. We also discuss the Mitoc-Malu Galben Gravettian in its wider regional context and implications for the Aurignacian-Gravettian transition

The Gravettian sequence of Mitoc-Malu Galben (Romania): New fieldwork between 2013 and 2016

In our presentation we will summarize results of fieldwork conducted at the Upper Palaeolithic open-air site Mitoc-Malu Galben in northeastern Romania. The site has a ~14m deep loess-paleosol sequence with a rather high climatic resolution. The chronostratigraphy is well established and embedded in this long sequence are abundant archaeological remains, mostly attributed to the Aurignacian and Gravettian. Our fieldwork between 2013 and 2016 provided new samples of the Aurignacian and Gravettian archaeological layers. Here we provide an overview of our fieldwork activities, the generated archaeological collections, and present a preliminary analysis of raw material economy and blank production and core exploitation strategies of the Gravettian assemblages. We also discuss the Mitoc-Malu Galben Gravettian in its wider regional context and implications for the Aurignacian-Gravettian transition

40 years of excavations at Mitoc–Malu Galben (Romania): changing fieldwork methodologies and implications for the comparability of archaeological assemblages

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/publishedVersio

40 Years of excavations at Mitoc-Malu Galben (Romania) : Exploring the archeology of a high-resolution loess-paleosol sequence

Mitoc–Malu Galben, with abundant Upper Palaeolithic archaeological layers embedded in a ~12 meters long loess-palaeosol sequence, is one of the key sites for the Upper Palaeolithic in Europe. The excavations in 1978–1990 yielded rich remains of Aurignacian and Gravettian workshops. From 1992 to 1995, their stratigraphical position, age and typological characteristics were better defined. Since 2013, our team has conducting new fieldwork focusing on: (i) the precise position and orientation of the archaeological remains through 3D recording with total stations, (ii) systematic wet-sieving of all excavated sediment, (iii) an interdisciplinary study of site formation processes, and (iv) a detailed technological study of the lithic artefacts. Our new field and lab research also aimed at integrating data from 40 years of work. Based on fieldnotes and drawings of the old two excavation periods and data from our new fieldwork, we constructed a GIS and database to assess artefact occurrences with reference to stratigraphic units, as well as their spatial distribution. We, thus, present an overview of the current knowledge about the site, with references to questions that remain open