Anne Crone

Radiocarbon (14C) wiggle-match dating is a technique with a substantial potential to improve the precision of dating timbers in situations where dendrochronology is not tenable. However, one of the key reasons why obtaining a dendrochronological determination might be difficult is the short-lived nature of timbers on a range of archaeological sites, something that also affects the efficiency of the wiggle-match dating technique. Combined with the potential for high expense that the technique presents, it is paramount that wiggle-match dating research design has a good empirical basis. To this end we dated 50 consecutive, individual rings from a timber that grew during the Hallstatt radiocarbon calibration plateau (ca. 750–400 cal BC) in southwest Scotland. The results indicate that (1) the precision and accuracy of wiggle-match dates carried out on short-lived sequences during the Hallstatt plateau may suffer due to insufficient resolution of the calibration data, (2) sampling time-frames roughly equivalent to the underpinning calibration data are recommended (for the period in question this means decadal blocks), and (3) short-lived sequences are at risk of losing accuracy if the actual past trend of radiocarbon diverges from the mean of the radiocarbon calibration curve.

Three timbers held in store at the National Museums of Scotland have been identified as the incomplete remains of a logboat that was found in the River Conon near Dingwall in 1874. Notwithstanding their poor condition, they were felt to justify dating (by both radiocarbon and dendrochronology), laser scanning (to create a ‘virtual’ reconstruction) and re-publication, subsequent to that by Mowat (1996: 22, 24, no 28 and 86, nos A21–22).  Radiocarbon dating showed the vessel to be of medieval date, while tree-ring evidence indicated that it was probably fashioned in the late 13th or early 14th centuries from an oak tree of some 300 years growth. This is the first logboat in Scotland to be dated by dendrochronology, and the results significantly extend the coverage of Scottish medieval tree-ring dates north of Inverness.  Specific features suggest that the remains may have formed one element within a vessel of paired (or possibly multiple) form, intended for the cross-river transport of heavy loads.

Dendroarchaeology almost exclusively uses ring-width (RW) data for dating historical structures and artefacts. Such data can be used to date tree-ring sequences when regional climate dominates RW variability. However, the signal in RW data can be obscured due to site specific ecological influences (natural and anthropogenic) that impact crossdating success. In this paper, using data from Scotland, we introduce a novel tree-ring parameter (Blue Intensity e BI) and explore its utility for facilitating dendro-historical dating of conifer samples. BI is similar to latewood density as they both reflect the combined hemicellulose, cellulose and lignin content in the latewood cell walls of conifer species and the amount of these compounds is strongly controlled, at least for trees growing in temperature limited locations, by late summer temperatures. BI not only expresses a strong climate signal, but is also less impacted by site specific ecological influences. It can be concurrently produced with RW data from images of finely sanded conifer samples but at a significantly reduced cost compared to traditional latewood density. Our study shows that the probability of successfully crossdating historical samples is greatly increased using BI compared to RW. Furthermore, due to the large spatial extent of the summer temperature signal expressed by such data, a sparse multi-species conifer network of long BI chronologies across Europe could be used to date and loosely provenance imported material.

An oak timber was discovered in 2013 within intertidal peats at the Bay of Ireland, Stenness, Orkney, representing a unique archaeological find. Subsequent excavation and rescue of the timber took place in 2014 to investigate its stratigraphical relationship before further eroding. Dendrochronological and morphological study identified the timber as a possible radially split log, c. 150 years of age when felled. No dendrochronological match was possible, and a wiggle-match date obtained provided a Later Mesolithic felling date of 4410–4325 cal BC. This timber is the first and only evidence so far for the use of oak in Mesolithic Orkney. The timber is significant palaeoecologically, suggesting oak may have been indigenous to Orkney. This adds to a growing argument for the existence of areas of “true woodland”. Pollen evidence shows the timber was deposited within reedswamp, fringed by willow-birch carr-woodland, with oak unlikely to have been growing in the immediate location. High microscopic and macroscopic charcoal values indicate Later Mesolithic communities' exerted influence on this wetland using burning as a tool for landscape modification. It is unknown what the timber represents; it may have been for construction purposes or as a marker/possible landing place showing the path to the Loch of Stenness.

Dendroarchaeology almost exclusively uses ring-width (RW) data for dating historical structures and artefacts. Such data can be used to date tree-ring sequences when regional climate dominates RW variability. However, the signal in RW data can be obscured due to site specific ecological influences (natural and anthropogenic) that impact crossdating success. In this paper, using data from Scotland, we introduce a novel tree-ring parameter (Blue Intensity e BI) and explore its utility for facilitating dendro-historical dating of conifer samples. BI is similar to latewood density as they both reflect the combined hemicellulose, cellulose and lignin content in the latewood cell walls of conifer species and the amount of these compounds is strongly controlled, at least for trees growing in temperature limited locations, by late summer temperatures. BI not only expresses a strong climate signal, but is also less impacted by site specific ecological influences. It can be concurrently produced with RW data from images of finely sanded conifer samples but at a significantly reduced cost compared to traditional latewood density. Our study shows that the probability of successfully crossdating historical samples is greatly increased using BI compared to RW. Furthermore, due to the large spatial extent of the summer temperature signal expressed by such data, a sparse multi-species conifer network of long BI chronologies across Europe could be used to date and loosely provenance imported material.

Title: The soggy road to a climatically sensitive 8000-year Scottish pine chronology. Authors: Wilson, Rob; Loader, Neil; Mills, Coralie; Crone, Anne; Edwards, Colin; Cunningham, Laura; Frith, Alex; Rydval, Milos. Affiliation: AA(St. ... Roslin, Edinburgh), AF(St. ...

Excavations were carried out at the crannog known as Dorman's Island, Whitefield Loch in Wigtownshire, SW Scotland as part of the Scottish Wetland Archaeology Programme. The excavation was limited in extent, but uncovered evidence for in-situ occupation layers, including laid oak flooring and a prepared clay surface. Finds included a range of coarse stone tools as well as fragments of glass bracelet and shard from a Roman drinking vessel. The timbers retrieved have yielded the first prehistoric dendrochronological dates in Scotland, placing the excavated floor in the earlier second century BC. This initial evidence correlates with evidence from the Irish dendrochronological record that suggests that construction on lochs may have occurred in irregular 'pulses' of activity- one of which was in the second century BC. The significance and potential of these results in the context of the northern British Iron Age are discussed.