Rehydroxylation of Fired‐Clay Ceramics: Factors Affecting Early‐Stage Mass Gain in Dating Experiments

To obtain accurate results in the RHX dating of ceramics, it is essential that the RHX measurements are continued until the rate of mass gain is constant with (time)^1/4. In this paper, we discuss how the initial stages of mass gain are affected by the specific surface area (SSA) of the ceramic material. The paper provides guidance on experimental protocols to avoid dating results being distorted by relatively early‐time mass gain data.     

A Post-Roman Sequence at Carlisle Cathedral

Excavations in 1988 revealed a stratigraphic sequence extending from the later Roman period to the twelfth century. Of particular interest and importance is a collection of Viking-Age metalwork which, with other material, sheds light on settlement in Carlisle before the arrival of the Normans in 1092.     

The integration of chronological and archaeological information to date building construction: an example from Shetland,Scotland, UK

This paper presents new chronological data applied to the problem of providing a date for the construction of a prehistoric building, with a case study from the Old Scatness Broch, Shetland. The innovative methodology employed utilises the combination of radiocarbon and optically stimulated luminescence (OSL) dates with the archaeological information, which includes the stratigraphic relationships of sampled deposits, context information, and evidence relating to the formation of the deposit. This paper discusses the scientific validity of the dates produced, and the advantages that the methodology employed at this site offers for archaeological interpretation. The combined dating evidence suggests that the broch at Old Scatness is earlier than the conventionally accepted dates for broch construction. More broadly it shows the value of integration of the specialists at the planning stages of the excavation. The application of a Bayesian statistical model to the sequences of dates allowed investigation of the robustness of the dates within the stratigraphic sequences, as well as increasing the resolution of the resulting chronology. In addition, the value of utilising multiple dating techniques on the same deposit was demonstrated, as this allowed different dated events to be directly compared as well as issues relating to the formation of the sampled deposit. This in turn impacted on the chronological significance of the resulting dating evidence, and therefore the confidence that could be placed in the results.     

An assessment of the magnetic response of an iron‐smelting site*

The magnetic response derived from an iron‐smelting site was investigated by comparing magnetometry and magnetic susceptibility geophysical survey data and laboratory analyses of the magnetic characteristics of the furnace and slags. Magnetic analysis and microscopy (optical and SEM) of samples from the furnace lining and the slag deposits demonstrated the heterogeneity in the magnetic, morphological and mineral compositions of both materials. The comparison of the magnetic characteristics of the material with the geophysical survey data illustrated the importance of using both magnetometry and magnetic susceptibility survey techniques to maximize the information from an iron‐smelting site. The furnace was dated archaeomagnetically to the 14th century ad . The results demonstrate that the magnetic analysis of iron‐smelting sites is highly valuable, both to characterize sites and to improve the understanding of early iron‐working technology.     

RHX Dating: measurement of the Activation Energy of Rehydroxylation for Fired‐Clay Ceramics

In rehydroxylation (RHX) dating, the activation energy of the rehydroxylation reaction is required first in the estimate of a material's effective lifetime temperature (ELT), and second to correct the RHX rate constant obtained at a given measurement temperature to that at the ELT. Measurement of the activation energy is thus integral to the RHX methodology. In this paper, we report a temperature‐step method for the measurement of activation energy and develop fully the underlying theoretical basis. In contrast to obtaining the activation energy from a series of separate experiments (each of which requires the sample to be dehydroxylated prior to measuring the RHX rate constant), the temperature‐step method not only requires a single dehydroxylation at 500°C but also eliminates repeated acquisition of Stage I data, which are not required for dating purposes. Since the first temperature step is set to correspond to the temperature at which a dating determination is carried out, the measurement of rate constants at higher temperatures simply becomes an extension of dating. Consequently, the logistics of obtaining the activation energy of rehydroxylation are greatly simplified.     

The Potential for Dating the Old Scatness Site,Shetland, By Optically Stimulated Luminescence

A series of deposits from the agricultural infield of the multiperiod settlement mound, Old Scatness, were investigated for their potential to yield optically stimulated luminescence dates. Luminescence properties of quartz grains were found to vary through the sequence, but dates were successfully obtained from five deposits, including anthropogenic soils, windblown sands and sands within midden deposits. Single‐aliquot equivalent dose measurement was found to be the most appropriate method for dating the deposits. The OSL dates obtained accorded well with the dates provided by archaeological evidence and included the post‐medieval, Iron Age, Bronze Age and Neolithic periods of Shetland, while a substantial midden was dated to the Bronze/Iron Age transition.     

Identifying archaeological wood stack charcoal production sites using geophysical prospection: magnetic characteristics from a modern wood stack charcoal burn site

Charcoal making was a common process in the woodlands of Britain for many centuries. However, historic ‘wood stack’ production sites are difficult to identify. This paper tests the hypothesis that geophysical survey is an appropriate method for the discovery and identification of archaeological charcoal making sites. A traditional wood stack charcoal kiln was constructed in Low Staindale, Dalby Forest, near Pickering, North Yorkshire, to investigate the charcoaling process and the effect of low-temperature carbonisation on the magnetic properties of the soil underlying the kiln. The results from temperature monitoring (within and beneath the charcoal stack) throughout the charcoaling process, geophysical surveys across the charcoal kiln platform, and laboratory analysis of soil and ash samples, are presented. The degree to which the magnetic properties of the ground beneath the charcoal kiln had been enhanced as a consequence of this low-temperature process is discussed. Whilst some magnetic enhancement to the soil beneath the kiln platform was recorded, enhancement appears to be the result of contamination from the wood stack sealing material rather than the effect of heat transfer resulting from the charcoaling process. The results suggest that whilst historic wood stack charcoal production sites are likely to remain an enigmatic and under-reported feature in the archaeological landscape, geophysical prospection does have the potential for identification of these sites.