A freshwater diet-derived C-14 reservoir effect at the Stone Age sites in the Iron Gates gorge

Human bones from single inhumation burials and artifacts made from terrestrial mammal (ungulate) bone found in direct association with the skeletons were obtained from the Stone Age site of Schela Cladovei situated just below the iron Gates Gorge of the River Danube. The results of stable isotope analyses of the human bone collagen are consistent with a heavy dependence on aquatic protein while radiocarbon dating of the samples reveals an offset of 300-500 years between the two sample types, indicating a freshwater reservoir effect in the human bone samples, Since protein consumption is by far the major source of nitrogen in the human diet we have assumed a linear relationship between delta(15)N and the level of aquatic protein in each individual's diet and derived a calibration for C-14 age offset versus delta(15)N which has been applied to a series of results from the site at Lepenski Vir within the gorge, The corrected C-14 ages (7310-6720 BP) are now consistent with the previous C-14 age measurements made on charcoal from related contexts (7360-6560 BP). In addition, the data indicate a change from a primarily aquatic to a mixed terrestrial/aquatic diet around 7100 BP and this may be argued as supporting a shift from Mesolithic to Neolithic. This study also has wider implications for the accurate dating of human bone samples when the possibility exists of an aquatic component in the dietary protein and strongly implies that delta(15)N analysis should be undertaken routinely when dating human bones

Radiocarbon and stable isotope evidence of dietary change from the Mesolithic to the Middle Ages in the iron gates: New results from Lepenski Vir

A previous radiocarbon dating and stable isotope study of directly associated ungulate and human bone samples from Late Mesolithic burials at Schela Cladovei in Romania established that there is a freshwater reservoir effect of approximately 500 yr in the Iron Gates reach of the Danube River valley in southeast Europe. Using the delta(15)N values as an indicator of the percentage of freshwater protein in the human diet, the C-14 data for 24 skeletons from the site of Lepenski Vir were corrected for this reservoir effect. The results of the paired C-14 and stable isotope measurements provide evidence of substantial dietary change over the period from about 9000 BP to about 300 BR The data from the Early Mesolithic to the Chalcolithic are consistent with a 2-component dietary system, where the linear plot of isotopic values reflects mixing between the 2 end-members to differing degrees. Typically, the individuals of Mesolithic age have much heavier delta(15)N signals and slightly heavier delta(13)C, while individuals of Early Neolithic and Chalcolithic age have lighter delta(15)N and delta(13)C values. Contrary to our earlier suggestion, there is no evidence of a substantial population that had a transitional diet midway between those that were characteristic of the Mesolithic and Neolithic. However, several individuals with "Final Mesolithic" C-14 ages show delta(15)N and delta(13)C values that are similar to the Neolithic dietary pattern. Provisionally, these are interpreted either as incomers who originated in early farming communities outside the Iron Gates region or as indigenous individuals representing the earliest Neolithic of the Iron Gates. The results from Roman and Medieval age burials show a deviation from the linear function, suggesting the presence of a new major dietary component containing isotopically heavier carbon. This is interpreted as a consequence of the introduction of millet into the human food chain

U-series dating of bone using the diffusion-adsorption model

U-series dating of bone has suffered problems of reliability since its inception because bone remains an open system with respect to uranium. Commonly applied a priori assumptions of U uptake, such as early uptake or linear uptake, are inadequate because they have no physical or chemical bases, no means of demonstrating which model is suitable for a particular bone, and no intrinsic tests of reliability. Despite this and numerous examples of anomalous U-series dates, such assumptions are still routinely applied. We address this problem using the diffusion-adsorption (D-A) model of U uptake (Millard and Hedges, 1996), which incorporates a physicochemical description of U uptake. Using this model, we show how the U uptake of a bone responds to geochemical changes in the burial environment, which can lead to phenomena such as the removal of U from bones (“leaching”) or U uptake late in their burial history (“recent uptake”), and we show how the overall uptake history is reflected in distributions (profiles) of U and U-series isotopes across a bone section. We present measurements of U concentration profiles, and 230Th/234U profiles on archeological bone from a number of different sites and burial environments and compare the results to profiles predicted by the D-A model. Bones that have undergone complex uptake histories (which include U leaching or recent uptake) are identified on the basis of these profiles and rejected as unsuitable for dating. For bones that appear to have undergone uptake under constant geochemical conditions, the D-A model is applied to calculate U-series dates, with much improved reliability

Dating a type site: fitting Szeleta Cave into its regional chronometric context

This paper considers the application of new dating strategies and protocols to the temporal position of Szeleta Cave, the Szeletian itself, and the Aurignacian of the Bükk mountains. In particular, it is advocated that the confusing chronological patterning seen for the Early Upper Palaeolithic of the Bükk mountains is largely the result of dating materials of uncertain anthropogenic origin and of incomplete removal of contaminants; hence we present here results of dating anthropogenically-modified bones, including bone, antler and ivory projectile points, using the ultrafiltration technique pioneered by the Oxford Radiocarbon Accelerator Unit. The results have yielded a possible explanation for the confusing pattern of dates seen for Szeleta cave, and also helped to extend the earliest-known osseous projectile points back to 37/38 ka 14C BP through the use of direct dating

Variations in bone collagen δ13C and δ15N values of fauna from Northwest Europe over the last 40 000 years

We report here a signal in the temporal variation of stable isotopes in protein from surviving animal bone in Northwest Europe over the past glacial cycle. There is a change in the average δ13C values of fauna in the Holocene, and there is also a significant reduction in δ15N values of herbivore bone collagen towards the end of the last glaciation, with a subsequent recovery soon after the start of the Holocene. This change is observed for several species and is restricted to those regions most affected by the glacial advance. Comparison with ice core data shows that there is a strong correlation between the average δ13C values of three herbivore species and ice core CO2 concentration. The data presented here show how readily available faunal bone collagen δ13C and δ15N measurements provide a record of past climate and environmental change on a regional to continental scal

The role of the environment in uranium uptake by buried bone.

Previous studies by a number of workers have shown that uranium is inhomogeneously distributed in excavated bones. It has been suggested that the higher concentrations of uranium found towards the outside of some bones may indicate that the uranium has been taken up by a diffusion process. This paper briefly outlines a quantitative model of uranium uptake by diffusion and chemical reaction, and the measurement of uranium distributions in a number of samples. The relationship of these distributions to environmental factors and to other diagenetic changes is explored, and comparisons made between them and the model. Finally the implications of these results for the uranium series dating of bones are considered, and the way forward in modelling uranium uptake suggested

A diffusion-adsorption model of uranium uptake by archaeological bone.

An argument for the possibility of uranium uptake by buried bone taking place through the adsorption of uranyl species on bone mineral is advanced. In the light of this a diffusion-adsorption model for uranium uptake by buried bone is developed, the necessary constants are evaluated from the literature and from laboratory measurements of the partition coefficient between solution and bone mineral. The geochemical and hydrological parameters which control uptake are discussed. The predictions of the model are shown to be in general accordance with the timescale, magnitude, and distribution of uranium uptake in archaeological bone. Using the model, specific predictions of the variation of apparent uranium-series ages in bone can be made, and bone is shown clearly not to conform to the closed system assumption. When the model is extended to tooth enamel it is found to be incompatible with the early uptake model used for ESR dating, but to fall between the early uptake and linear uptake models. Similarly, it suggests that uranium-series dates on enamel assuming a closed system are liable to underestimate the true age by at least one-third

Bones and groundwater: towards the modelling of diagenetic processes.

This paper develops a theory for describing those diagenetic changes in bone which involve its interaction with groundwater. Three main processes are considered, as examples of such changes; namely the uptake of uranium, the dissolution of bone, and the increase of crystallinity of the bone mineral (carbonate hydroxyapatite or dahllite). Here simple models of the chemistry involved are postulated (although how bone interacts with water on a molecular scale is not clearly known) in order to demonstrate the theory with explicit mechanisms and values. Greater emphasis is given to uranium uptake, since the model used is comparatively detailed, being based on the authors' previous work. The basic assumption is that the rate-limiting process in diagenetic change is the movement of solutes to, from, or how the physical structure of the bone itself, together with the hydrology of the burial site, interact to determine how water and its solutes move into, within and from a bone during burial. This interaction can be of three kinds, defined by the site hydrology. These are termed here, diffusion, hydraulic flow and recharge. All three types may operate together, and their relative importance depends on the extent to which the pore structure of a bone has been altered by diagenesis, as well as the type of chemical change taking place. It is shown that diffusion is usually the most common and important process, but that it is possible to predict the hydrological regimes in which other mechanisms dominate. It is shown how knowledge of site hydrology (mainly the specification of soil structure and moisture variation), the physical state of the bone, and the chemistry of the diagenetic observation, suggesting this approach to be on the right lines. Qualitative predictions also result from the theory. The main value of this approach is to identify those situations where particular diagenetic changes are simplest (e.g. sites where the hydrology gives rise to a single and quantifiable hydraulic process) so that they may be decisively tested against the quantitative predictions of the theory