The freshwater reservoir effect can result in anomalously old radiocarbon ages of samples from lakes and rivers. This includes the bones of people whose subsistence was based on freshwater fish, and pottery in which fish was cooked. Water rich in dissolved ancient calcium carbonates, commonly known as hard water, is the most common reason for the freshwater reservoir effect. It is therefore also called hardwater effect. Although it has been known for more than 60 years, it is still less well-recognized by archaeologists than the marine reservoir effect. The aim of this study is to examine the order of magnitude and degree of variability of the freshwater reservoir effect over short and long timescales. Radiocarbon dating of recent water samples, aquatic plants, and animals, shows that age differences of up to 2000 14 C years can occur within one river. The freshwater reservoir effect has also implications for radiocarbon dating of Mesolithic pottery from inland sites of the Ertebølle culture in Northern Germany. The surprisingly old ages of the earliest pottery most probably are caused by a freshwater reservoir effect. In a sediment core from the Limfjord, northern Denmark, the impact of the freshwater reservoir effect on radiocarbon dating in an estuarine environment is examined. Here, freshwater influence causes reservoir ages to vary between 250 and 700 14 C years during the period 5400 BC -AD 700. The examples in this study show clearly that the freshwater reservoir effect can seriously corrupt radiocarbon dating at inland sites. Reservoir effects should therefore be considered whenever food remains on pottery or the bones of omnivores are radiocarbon dated -irrespective of the site's distance to the coast.

The freshwater reservoir effect is a potential problem when radiocarbon dating fish bones, shells, human bones, or food crusts on pottery from sites near rivers or lakes. The reservoir age in hardwater rivers can be up to several thousand years and may be highly variable. Accurate 14C dating of freshwater-based samples requires knowing the order of magnitude of the reservoir effect and its degree of variability. Measurements on modern riverine materials may not give a single reservoir age correction that can be applied to archaeological samples, but they show the order of magnitude and variability that can also be expected for the past. This knowledge will be applied to the dating of food crusts on pottery from the Mesolithic sites Kayhude at the Alster River and Schlamersdorf at the Trave River, both in Schleswig-Holstein, northern Germany.

a b s t r a c tThe pottery investigated in this study comes from late mesolithic inland sites next to rivers in Northern Germany. The first AMS 14 C datings of food crusts from these sites showed surprisingly high ages, which could be caused by the hardwater effect.Modern samples from the rivers have ages of several hundred 14 C years, and a modern food crust prepared from fish with a certain reservoir age shows the same age as the fish. Surprisingly, there was a large age difference between water samples and fish/mollusc shell from the same river. Associated archaeological samples of terrestrial and fluvial origin show age differences of several hundred and up to 3000 years. These high age differences are only to a limited extent transferred to the archaeological food crusts.

Palaeoenvironmental and 14 C reservoir age variability in the Limfjord, a sound through northern Jutland, Denmark, was investigated for the period 7300 to 1300 cal yr BP. Shells and bulk sediment samples from a core from a former inlet, Kilen, were analysed by radiocarbon dating and stable isotope (C/N) measurements. A strong correlation between the C/N ratios and δ 13 C values verifies that these are good carbon source indicators and thus allow environmental reconstructions. Furthermore, δ 13 C values are correlated with salinity in the photic zone, inferred quantitatively from diatom assemblages. They are therefore used to differentiate between brackish and marine palaeo-conditions. 14 C reservoir ages of shells vary from ΔR=−140 to +300 14 C years. Between 7300 and 5400 cal. yr BP, reservoir age and stable isotope values are highly variable and indicate mixing of marine water and brackish surface waters with hard water effects. After 5400 cal. yr BP, the ΔR values stabilise and show an increasingly marine environment, with 14 C reservoir ages close to 400 years (ΔR=0). After 2000 cal. yr BP, Kilen becomes brackish. Reservoir ages and stable isotope values are again highly variable and δ 13 C and C/N values are no longer correlated. Before 4000 cal. yr BP, δ 15 N values vary by only 1‰ and do not reflect the changes in the marine environment. A δ 15 N increase between 3500 and 2000 cal. yr BP signifies enhanced organic productivity or a change in agricultural practices.

No abstract

The socio-cultural and economic developments that took place from the Neolithic to the Bronze Age are poorly understood, despite the fact that they were essential for the establishment of fully agro-pastoral economies in Europe. In this study, we aim to assess dietary changes in communities living in southern Italy during this period by examining stable carbon and nitrogen isotope ratios on human bone collagen. In particular, we investigated skeletal remains from seven sites in the southern Italian regions of Calabria (Grotta della Monaca, Grotta di Donna Marsilia and Grotta dell’Antenato), Basilicata (Murgia Timone, Grotta Funeraria and Toppo d’Aguzzo) and Apulia (Ipogeo dei Bronzi) to explore possible variations in diet between different geographic areas and periods. The results of the analysis on bone collagen extracts from 33 human and 12 faunal (sheep, dog, cattle and pigs) specimens attest that the diets of prehistoric southern Italians were mixed and based on the consumption of terrestrial resources, including generally moderate proportions of animal protein (e.g. meat and dairy products) and of C3 plants (e.g. cereals and legumes). Minor differences in the proportion of consumed meat are mostly dependent on the nature of regional environments, with individuals from Basilicata relying more on animal protein than those from Calabria and Apulia. Our study provides insights into the dietary habits of southern Italian populations during the prehistoric period that witnessed an increase both in agriculture and in pastoralism.

The radiocarbon (14C) calibration curve so far contains annually resolved data only for a short period of time. With accelerator mass spectrometry (AMS) matching the precision of decay counting, it is now possible to efficiently produce large datasets of annual resolution for calibration purposes using small amounts of wood. The radiocarbon intercomparison on single-year tree-ring samples presented here is the first to investigate specifically possible offsets between AMS laboratories at high precision. The results show that AMS laboratories are capable of measuring samples of Holocene age with an accuracy and precision that is comparable or even goes beyond what is possible with decay counting, even though they require a thousand times less wood. It also shows that not all AMS laboratories always produce results that are consistent with their stated uncertainties. The long-term benefits of studies of this kind are more accurate radiocarbon measurements with, in the future, better quantified uncertainties.

This paper discusses the problem of the freshwater reservoir effect in the radiocarbon dating of different sample materials, in particular food crusts on pottery. Charred food residue can be used to directly date of the use of the pottery. However, this material is highly complex, which can lead to various dating errors.