Offre de thèse : Unearthing the secrets of hill-fort vitrification in early European history (Aberdeen)

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Vitrified hillforts, whose walls have been destroyed by the melting and fusing of outer rock walls through fire, are found throughout Europe, with a significant concentration occurring across Scotland. Those specific to Scotland have been dated from the Bronze age to early Medieval period, suggesting a long-cultural significance to fort vitrification. The circumstances and methods involved in the vitrification of hillforts, however, remain heavily debated. The process of rock vitrification requires a considerable understanding of fire technology, in order to get temperatures capable of melting rock in pervasive temperatures exceeding 1000°C, with the outcome being a mineral ‘glass’. In contrast, achieving these temperatures in contemporary settings requires complex equipment and experimental processes. This raises considerable questions as to the possibility, means and aims of fort vitrification in early European history. An interdisciplinary application of earth science analyses - including rock geochemistry, Raman spectroscopy, and palaeoecology – offers a unique opportunity to investigate how and why fort vitrification was achieved. To answer this, the project will be divided into two main parts. The first component of the studentship will involve identifying and sampling rock, vitrified glasses, and charcoals from two different hillforts (one in Scotland, and the other in Europe). Rock and glass samples will be used to conduct mineral analysis to understand changes in rock chemistry during vitrification, and olivine geothermometry (calculating temperatures of melt from olivine cooling rates). Charcoals, encased within the glass, will be analysed using Raman spectroscopy to calculate the temperatures experienced during the fires. This research will also involve extensive application of the new scanning electron microscope in the School of Geosciences, University of Aberdeen. Comparing and calibrating these methods will help understand and develop new methods of geothermometry, specific to hillfort vitrification. The second part of this project will include sampling soil and/or peat from the environs of each hillfort to identify potential windblown charcoals and pollutant geochemistry that may correspond to the vitrification event. Charcoals and peat/soil chemistry will then be analysed, alongside pollen and macrofossil study, to quantify the types of fuels and accelerants that may have been used during vitrification. These data will offer insight into how hillfort sites, separated geographically and culturally, were vitrified using different fuels, rock types, and environmental conditions.

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