Informing Conservation: Towards ¹⁴C Wiggle-Matching of Short Tree-Ring Sequences from Medieval Buildings in England

Abstract

This study tested whether accurate dating by AMS radiocarbon wiggle-matching short tree-ring series (c. 30 annual rings) in the medieval period could be achieved., Scientific dating plays a central role in the conservation of historic buildings in England. Precise dating helps assess the significance of particular buildings or elements of their fabric, thus allowing us to make informed decisions about their repair and protection. Consequently considerable weight, both financial and legal, can be attached to the precision and accuracy of this dating. Dendrochronology is the method of choice, but in a proportion of cases this is unable to provide calendar dates. Hence we would like to be able to use radiocarbon wiggle-matching to provide a comparable level of precision and reliability, particularly on shorter tree-ring sequences (c. 30 annual growth rings) that up until now would not routinely be sampled. We present the results of AMS wiggle-matching five oak tree-ring sequences, spanning the period covered by the vast majority of surviving medieval buildings in England (c. AD 1180-1540) when currently we have only decadal and bidecadal calibration data BackgroundOver the past 25 years scientific dating has become an integral part of the processes for conservation and repair of historic buildings in England. Precise dating informs decisions about the preservation of buildings, allows us to identify significant fabric, and aids in the specification of appropriate repair strategies. Small differences in date can lead to great differences in the significance of the extant building, and thus to great differences in the costs of the agreed solution for a particular case.Outcomes of this sort clearly demonstrate the value of precise dating in informing repair and conservation decisions for historic buildings, and have led to dendrochronology becoming widely applied as part of these processes. In consequence, Historic England (and its predecessor, English Heritage) alone has funded tree-ring dating on more than 1500 buildings over the past 20 years to inform such decisions. The ProblemIn providing the required precise dating for historic buildings in England, the scientific dating method of choice is dendrochronology. The vast majority of medieval buildings in England are constructed of oak, which is widely and successfully dated (English Heritage 1998). There are three situations, however, in which tree-ring analysis may fail to produce calendar dating. 1) When a building produces oak tree-ring sequences which simply do not match against the available reference chronologies, 2) When a building is constructed from a species other than oak, 3) When the timbers in a building contain less than the 50 rings which is normally required for successful dendrochronology.Of these three situations, the length of the available oak tree-ring sequences is by far the most common limitation. It is clear that the probability that an oak sequence will remain undated is inversely related to the number of tree-rings in the sequence ...

Fluctuating radiocarbon offsets observed in the southern Levant and implications for archaeological chronology debates

“…( B ). OxA data on other known age NH tree rings ( 61 , 62 ) versus IntCal13 ( 1 ). ( C ) Overall 14 C years offset OxA NH data in B versus IntCal13; light gray region shows the neutral prior (0 ± 20) versus the calculated posterior region (blue) ( 27 ).…”

The Influence of Calibration Curve Construction and Composition on the Accuracy and Precision of Radiocarbon Wiggle-Matching of Tree Rings, Illustrated by Southern Hemisphere Atmospheric Data Sets from AD 1500–1950

“…The wider envelope on the SHCal13-NEW curve means that when calibrating a radiocarbon determination against it, the credible range for the object's unknown age will generally be wider than the interval obtained by calibrating against SHCal13-RWM, the latter we consider unrealistically precise. Since Bayliss et al (2017) demonstrated that the calendar age range intervals obtained using SHCal13-RWM can be too narrow and provide overly-precise calibration in places, the wider SHCal13-NEW will hopefully provide better calibration accuracy and credible age range coverage.…”

Refining the Hallstatt Plateau: Short-Term14C Variability and Small Scale Offsets in 50 Consecutive Single Tree-Rings from Southwest Scotland Dendro-Dated to 510–460 BC

“…Furthermore, because both Galimerti et al (2004) and Goslar and Madry (1998) relied on data simulated from the calibration curve, their studies had no potential for identifying any of the issues that may arise in empirical data. The importance of this empirical evaluation becomes clear once we consider the very recent study of the performance of short-span wiggle-matches in the context of medieval buildings in England (Bayliss et al 2017). Within this study three out of the five dated sequences failed to reproduce the known dendrochronological date for the felling of the timbers.…”