A02_P01

Direct and Indirect Attempts at Diachronic Quantification of the Marine Reservoir Effect

Niedospial J¹, Sevink J², Maurer A, Mazzini I⁴, Arienzo I⁵, Kuijper W⁶, van Hall R², Dee M¹

¹Centre for Isotope Research, University of Groningen, Groningen, Netherlands, ²Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands, ³Groningen Institute of Archaeology, University of Groningen, Groningen, Netherlands, ⁴Institute of Environmental Geology and Geoengineering, National Research Council of Italy, Rome, Italy, ⁵National Institute of Geophysics and Volcanology, Naples, Italy, ⁶Faculty of Archaeology, Leiden University, Leiden, Netherlands

The marine reservoir effect (MRE) is fundamental to understanding the carbon cycle and for correction of radiocarbon dates on samples either partially or wholly derived from marine carbon. Estimates of the offset commonly make use of paired samples of contemporary marine and terrestrial material, with the resultant offset then applied to the time period of interest. Paradoxically, it is widely accepted that the MRE at any one location is likely to have fluctuated over time, calling into question the validity of such retrojections. In this

study, we set out to both calculate the MRE for a specific location and then to understand the dynamics behind its variation over time using an array of geochemical and palaeoecological proxies. Previous research at our study site of Puntone, on the Tyrrhenian Sea, revealed that the area had transitioned between open marine, lagoonal and terrestrial regimes, and hence the local MRE was likely to have altered over time. This expectation was confirmed by the new radiocarbon data we obtained on marine shells and terrestrial plant remains. First attempts at using metal ion and isotope ratios through the core to elucidate, and indeed model, the MRE fluctuations have shown signs of promise but additional research is required to develop these approaches.

A02_P02

Variability of Radiocarbon reservoir age effects in lakes and rivers of Eastern Anatolia and Lesser Caucasus

FONTUGNE M^1,2, HATTÉ C^2,3, TISNÉRAT-LABORDE N², OLLIVIER V¹, KUZUCUOGLU C⁴

¹LAMPEA, Aix-en-Provence, France, ²LSCE - CEA, Gif-sur-Yvette, France, ³Silesian University of Technology, Gliwice, Poland, ⁴Laboratory of Physical Geography , Meudon, France

Multiproxy sedimentary sequence analysis constitutes the basis for reconstructions of past paleoenvironments and climate evolution. These sequences are, for the most part, obtained by coring in lakes (maar or crater) whose waters can record volcanic activity or karstic contributions, especially in Eastern Anatolia and the Lesser Caucasus. The main consequence is to generate a reservoir age effect and to bias the radiocarbon dates of sedimentary records from these lakes. In the same way, the halieutic resources bordering these lakes also record this reservoir effect. And, as they constitute the food resources of the local populations, this reservoir effect is also reflected in the skeleton of the lake population. We present, here, some results obtained from eastern Anatolian lakes, Van and Sevan lakes and from archaeological sites along the Kura river and its tributaries from Lesser Caucasus.

A02_P03

Identification of marine reservoir effect in the Holocene sediments from the Nobi Plain, central Japan

Nakanishi T¹, Hori K², Nakashima R³, Hong W⁴

¹Museum of Natural and Environmental History, Shizuoka, Japan, ²Department of Earth Science, Tohoku University, Sendai, Japan, ³Geological Survey of Japan (GSJ), Advanced Industrial Science & Technology (AIST), Tsukuba, Japan, ⁴Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea

To investigate the relationship between paleoenvironmental changes and marine reservoir effects, the radiocarbon ages of marine shells and terrestrial plants were measured from the same horizons of the Holocene sediments. Two sediment cores, HN1 and OG, were obtained from the western margin of the Nobi Plain, which faces the Kuroshio warm current. This plain is a fluvial–coastal lowland formed mainly by Kiso, Nagara, and Ibi rivers (Hori et al., 2019). These drilling sites are located in subsidence area associated with the Yoro fault (Kuwahara, 1968; Ishiyama et al., 2007). Based on analyses of lithology, molluscan assemblages, and radiocarbon dating, we interpreted five sedimentary units in order of older age: estuary, prodelta, delta front, delta plain, and artificial soil. These paleoenvironmental changes had been mainly associated with the sea-level rise during the deglacial period. Terrestrial accumulation curve was consistent with the Kikai-Akahoya volcanic ash (K-Ah: ca. 7,300 cal BP; Machida and Arai, 2003). The reservoir ages during the period from 9,300 to 2,800 cal BP of 13 pairs obtained from the estuary to delta front facies were evaluated. The average from 140 ± 70 to 900 ± 50 was 350 ± 180 years. The chronological change in the reservoir effect will be compared with the previous results from the other coastal area in Southwest Japan (Nakanishi et al., 2017ab, 2019). Drilling program of the sediment cores were supported by the Grants-in-Aid for Scientific Research, Kakenhi JP17K18526. Radiocarbon dating was funded by the JSPS Kakenhi grant number JP18H01310.

A02_P04

Time varying Local Marine Reservoir Effect in Coastal Systems

Macario K¹, Alves E¹, Oliveira F¹, Chanca I², Scheel-Ybert R³, Gaspar M³, Tenorio C³, Dias F¹, Aguilera O¹, Bianchini G³, Vitorino B¹, Cardoso R¹, Anjos R¹, Muniz M¹

¹Universidade Federal Fluminense, Niteroi, Brazil, ²Max Planck Institute, Jena, Germany, ³Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

The radiocarbon (¹⁴C) Marine Reservoir Effect (MRE) is known to vary with time due to global environmental changes, now better represented by the Marine20 calibration curve. In coastal regions, however, the scenario is considerably more complex and the MRE is influenced by carbon sources that exhibit a wide range of isotopic signatures. Indeed, the complexity of the carbon cycle in coastal systems demands extensive research for an accurate quantification of the MRE and its variability, which has the effect of hindering accurate ¹⁴C chronologies on the coast. The local MRE offset (∆R) in estuaries, is subject of the interplay of the hydrography with factors such as the regional geology, upwelling and sea-level variations. Using paired archaeological samples from the Southeastern coast of Brazil, we show a highly variable MRE and a possible correlation with the sea level regression.

A02_P05

Freshwater reservoir effects in charred ‘food crusts’ on pottery: frequency, magnitude, risk factors and prospects for correction

Meadows J^1,2, Lucquin A³, Gonzalez Carretero L^3,4, Dolbunova K^4,5, Craig O³, Heron C⁵

¹ZBSA (Centre for Baltic and Scandinavian Archaeology), Kiel, Germany, ²Christian-Albrechts-Universität zu Kiel, Leibniz-Labor für Altersbestimmung und Isotopenforschung , Kiel, Germany, ³BioArCh, University of York, York, United Kingdom, ⁴Department of Scientific Research, The British Museum, London, United Kingdom, ⁵State Hermitage Museum, St Petersburg, Russia

The ERC-funded INDUCE project is concerned with the adoption of pottery by hunter-gatherer-fishers in northeastern Europe. In this region and period, it is often difficult to date pottery find contexts, but potsherds often have carbonised deposits (‘food crusts’, FCs). Thus ¹⁴C dating of FCs is desirable, but these FCs probably contain carbon from aquatic organisms with unknown ¹⁴C reservoir effects. The problem is more salient at inland sites, given the potential scale of freshwater reservoir effects (FREs).

To investigate pottery function, INDUCE has acquired EA-IRMS data (%C, %N, δ¹³C, δ¹⁵N) on FCs on more than 400 sherds, from over 50 sites. In most cases we have also obtained biomarker (GC-MS) and compound-specific δ¹³C (δ¹³C16:0, δ¹³C18:0) data on soluble lipids extracted from the same FC. Some FCs have also been examined by SEM-EDX microscopy. These analyses confirm that FCs are composed primarily of food remains, which are dominated by aquatic species.

We have dated more than 100 FCs, often when their context date, and/or local FRE, is well-constrained. We have tested whether any combination of isotopic, biomolecular and microscopic data predicts apparent ¹⁴C age offsets in FCs. Contrasting results from sites with >10 dated FCs illustrate the scope for using FC ¹⁴C to date hunter-gatherer-fisher pottery. Where FC ingredients are more varied, a multi-proxy approach appears to account for most of the variation in FC offsets, but at other sites, FC composition is too uniform, and FREs are too varied, to justify attempts at FC ¹⁴C-age ‘correction’.

A02_P06

Estimating freshwater reservoir ages using Bayesian models for the Mesolithic to neolithic transition

Olsen J¹, Maaring R¹, Mannino M¹

¹Aarhus University, Aarhus, Denmark

The chronology of the Mesolithic to Neolithic transition is difficult to date accurately using radiocarbon analysis on human or animal bone remains. This is because that in particular the hunter-gather culture of the Mesolithic involves diets from multiple sources. When both marine and freshwater food webs are exploited, it becomes difficult to correct the radiocarbon ages for possible reservoir effects. In particular, the freshwater reservoir effect is unknown and expected to vary substantially. We have collected a large dataset of dog bones across the Mesolithic to Neolithic transition from which we have deduced the percentage of terrestrial, marine and freshwater diets using a FRUITS model. Further, we have included a dataset of domesticated cattle. All from multiple sites across Denmark. We have constructed a Bayesian model with phases based on the archaeological typology, i.e. belonging to either Mesolithic or Mesolithic. In the model we have allowed for estimating the total reservoir age using a wide uniform prior. If we assume that the marine reservoir age is known then the freshwater reservoir age can be estimated from the posterior total reservoir age probability distribution. The calculated freshwater reservoir age vary from a few hundred ¹⁴C years and up 1200 ¹⁴C years. Further, we have tested the robustness using different Bayesian model of the Mesolithic to Neolithic transition and found our freshwater reservoir estimates are similar and independent of model choice.

A02_P07

Reservoir Effect determination in marine shells from Mexico

Rodriguez-Ceja M¹, Díaz-Castro M², Solis C¹, Álvarez-Lajonchere L³, Méndez-García C^1,4, Chávez-Lomelí E¹

¹Universidad Nacional Autónoma de México, Mexico City, Mexico, ²2 Instituto Superior de Tecnologías y Ciencias Aplicadas. Universidad de La Habana, Cuba., La Habana, Cuba, ³Museo de Historia Natural Felipe Poey. Universidad de la Habana, Cuba. , LA Habana, Cuba, ⁴Cátedras Conacyt. Instituto de Física. Universidad Nacional Autónoma de México. , Mexico City, Mexico

When trying to establish the chronology of a site through radiocarbon dating, terrestrial samples are usually preferred. However, since they are not always available, an alternative is the use of malacological material from marine organisms as mollusks.

Given that radiocarbon activity in aquatic environments is usually different from that of the atmosphere, organisms that grow in both environments have different apparent ages, even though they are contemporary. This apparent age is known as “reservoir effect” and varies depending on latitude and other local factors.

Mexico is a country with a littoral of more than 11,000 Km, and a great interest in dating malacological samples from coastal contexts.   However, reservoir effect studies are still scare. Must of the available data come from studies done in the 60s and 90s decades, of the XX century.

We present new reservoir effect data from coastal Mexican sites in the Pacific Ocean and the Caribbean Sea, obtained from a Collection of Mexican shells samples belonging to the Natural History Museum Felipe Poey, from the Universidad de La Habana, Cuba and to the Institute of Biology of the Universidad Nacional Autónoma de México.