Scottish vitrified forts: Background and potential for TL dating

Sanderson, D.C.W.; Placido, Frank; Tate, J.

doi:10.1016/0735-245x(85)90093-6

Cited by 10 publications

(10 citation statements)

References 8 publications

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“…To explore the first-order variability in μ , we have employed both bulk- and glass-compositional data from the walls of 45 Iron Age forts across Europe (including experimentally produced glass from partial-melts of protoliths)1341214 and reference material compositions of Moine assemblages from Scotland31 together with a multicomponent silicate liquid viscosity model23 in order to obtain the composition-dependence of the fragility m of the liquid viscosity. The fragility is a measure of the temperature-dependence of the viscosity in the high viscosity region (close to the glass transition of the liquid intersected at a cooling rate of 5 K.min −1 ) and is given by23…”

Section: Results: the Evolving Properties Of Vitrified Enclosure Wallsmentioning

confidence: 99%

“…( a ) The liquid fragility m for 44 vitrified fort compositions1341214 or the partial melts thereof constructed in the Iron Age across Europe and Scottish Moine assemblage reference samples31 as a function of the silica content (when normalized by the total measured element abundance). ( b ) A map of Scottish fort locations with corresponding simplified bedrock geology.…”

Section: Figurementioning

confidence: 99%

“…Approximately 200 examples exist which are known to bear evidence for at least partial vitrification134. The best-studied examples occur in Scotland12.…”

mentioning

confidence: 99%

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Local geology controlled the feasibility of vitrifying Iron Age buildings

Wadsworth

Heap

Damby

et al. 2017

Sci Rep

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During European prehistory, hilltop enclosures made from polydisperse particle-and-block stone walling were exposed to temperatures sufficient to partially melt the constituent stonework, leading to the preservation of glassy walls called ‘vitrified forts’. During vitrification, the granular wall rocks partially melt, sinter viscously and densify, reducing inter-particle porosity. This process is strongly dependent on the solidus temperature, the particle sizes, the temperature-dependence of the viscosity of the evolving liquid phase, as well as the distribution and longevity of heat. Examination of the sintering behaviour of 45 European examples reveals that it is the raw building material that governs the vitrification efficiency. As Iron Age forts were commonly constructed from local stone, we conclude that local geology directly influenced the degree to which buildings were vitrified in the Iron Age. Additionally, we find that vitrification is accompanied by a bulk material strengthening of the aggregates of small sizes, and a partial weakening of larger blocks. We discuss these findings in the context of the debate surrounding the motive of the wall-builders. We conclude that if wall stability by bulk strengthening was the desired effect, then vitrification represents an Iron Age technology that failed to be effective in regions of refractory local geology.

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Section: Results: the Evolving Properties Of Vitrified Enclosure Wallsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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Local geology controlled the feasibility of vitrifying Iron Age buildings

Wadsworth

Heap

Damby

et al. 2017

Sci Rep

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“…Sanderson and Placido (1985) studied variations in the count rate recorded above a threshold by a NaI (Tl) spectrometer as a function of depth in Scottish vitrified forts. It has been shown that the threshold technique provides more precise results in a shorter amount of time (see Miallier et al, 2009).…”

Section: Gamma Dose Rate Determination From Surface Measurementsmentioning

confidence: 99%

“…If in the case of sediment grains dating, gamma radiation will contribute approximately 30% to the total dose rate, this component may go up to 80% in the case of archaeological stone artifacts (flint, quartzite, etc.). Precise ages are therefore dependent on a good knowledge of the gamma dose rate received by the object when buried, and this parameter is particularly difficult to determine in sites where heterogeneous environments result in high spatial variability of this physical quantity (e. g. Aitken, 1985;Aitken et al, 1985;Sanderson and Placido, 1985;Mercier et al, 1995;Brennan et al, 1997). Actually, one should make in that case a measurement of the gamma dose rate at the exact location where the sample comes from (by inserting a dosimeter or a portable gamma spectrometer).…”

Section: Introductionmentioning

confidence: 99%

Field gamma spectrometry, Monte Carlo simulations and potential of non-invasive measurements

Guérin

Mercier

2011

Geochronometria

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Abstract:The determination of gamma dose rates is of prior importance in the field of luminescence dating methods. In situ measurements are usually performed by the insertion of dosimeters or a portable gamma spectrometer cell in sediments. In this paper, Monte-Carlo simulations using the GEANT4 toolkit allow the development of a new technique of in-situ gamma dose rate evaluations: a spectrometer cell is placed on the surface of sediments under excavation to acquire successive spectra as sediments are removed by excavations. The principle of this non-invasive technique is outlined and its potential is discussed, especially in the case of environments in which radioelements are heterogeneously distributed. For such cases, a simple method to reconstruct gamma dose rate values with surface measurements using an attenuator is discussed, and an estimation of errors is given for two simple cases. This technique appears to be applicable, but still needs experimental validation.

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