Improving the 14C dating of south-west Scottish wetland sites

Jacobsson, Piotr (2015) Improving the 14C dating of south-west Scottish wetland sites. PhD thesis, University of Glasgow.

Abstract

This thesis discusses the adaptation of the wiggle-match dating technique and Bayesian chronological models to the practicalities of dating timbers from Iron Age Scottish wetland sites, with a focus on the area between the firths of the rivers Clyde and Solway. Wiggle-match dating technique relies on taking measurements from a sequence with an estimated, or known deposition rate, such as timbers, and fitting the resultant time series to an established calibration curve. Bayesian modelling entails combining various forms of information about the material dated to obtain a more comprehensive chronological understanding. These techniques are relevant to Iron Age wetland settlement in Scotland due to the lack of other methods that could produce high-precision dates on a routine basis; too few timbers from Scottish wetlands produce absolute dendrochronological dates and ordinary radiocarbon calibrations tend to have low precision during the period 750-200 BC, which covers the formative stages of both the Scottish Iron Age and wetland settlement tradition.
Effective use of the wiggle-match dating technique requires attention to aspects of technique, its practical implementation and suitable research design. As far as technical aspects are concerned, the work conducted within this thesis demonstrated the need to match the length of sample blocks of wood with the length of the measurements underpinning the calibration curve. Furthermore, presence of small offsets between the calibration curve and the actual past trend of radiocarbon has been identified; while these offsets have minimal impact on most radiocarbon applications, the wiggle-match dating technique is sensitive to them and hence conscious decisions need to be made at the stage of research design to avoid systematic bias in the results. Aspects of practical implementation have been explored through wiggle-match dating studies at four sites: Black Loch of Myrton, Cults Loch 3, Dumbuck and Erskine Crannog. Results demonstrate that even on the most challenging parts of the calibration curve wiggle-match dating can succeed in producing modelled date ranges of less than 100 years and that, on more favourable parts of the curve, it can be used to aid the resolution of questions regarding site formation processes. Moreover, these case studies highlighted a number of practical issues such as propensity of decayed rings to produce radiocarbon results biased towards older ages. Efficient use of wiggle-match dating in archaeological contexts requires not only the technical and practical capacity, but also a strategic framework within which the methodology is to be employed. While the nature of this framework depends on the interpretations the researcher is interested in, this thesis suggests a focus on developing linkage between different sites, both wetland and terrestrial, so that the well-preserved deposits become informative of not only a single site, but also shed light on the local and regional developments.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: crannogs, radiocarbon, wiggle-match dating, single-ring dating, dating strategies.
• Subjects: C Auxiliary Sciences of History > CC Archaeology
• Colleges/Schools: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Supervisor's Name: Cook, Professor Gordon T. and Hamilton, Dr. W. Derek
• Date of Award: 2015
• Depositing User: Dr Piotr Jacobsson
• Unique ID: glathesis:2015-7231
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 08 Apr 2016 14:54
• Last Modified: 28 Apr 2016 08:09
• URI: https://theses.gla.ac.uk/id/eprint/7231