Sapwood estimates in the interpretation of tree-ring dates

Many timber finds lack some or all of the outer, sapwood rings formed in the years just before felling. In order to estimate felling date once the outermost remaining ring has been dated, it is necessary to estimate the number of sapwood rings originally present. Methods doing this for oak are reviewed in the light of an intensive study of living trees at one site and an extensive study of 175 samples from living trees in North Wales and northwest England. Some methods reported in the literature are found to be invalid. A method reported by Hollstein (1965) is most reliable, with modifications for known variations in sapwood number with position in the tree. At present the best available estimate is that a value of 30 sapwood rings be used (95% confidence limits: 19–50).     

Out of the Peat: Preliminary Geophysical Prospection and Evaluation of the Mid-Holocene Stationary Wooden Fishing Structures in Haapajärvi,Finland

The huge scientific and interpretive value of wetland archaeological sites has been well demonstrated in several studies. The management of the archaeological resource of wetland landscapes is problematic, however, and there is an urgent need for noninvasive techniques to detect waterlogged organic archaeological remains. Stationary wooden fishing structures associated with fishing sites constitute an important wetland archaeological resource in northern Europe. In Finland, similar wooden constructions have been used for fishing from prehistory to the early modern era. The discovery of sites has been accidental, because the waterlogged organic remains have been considered invisible to conventional geoprospection techniques. Because of this, a small project was launched at Lamminoja, northwest Finland, in order to investigate whether it would be possible to improve our chances to detect fishery sites in demanding wetland habitats. New information was obtained through geophysical prospection, trial excavations, and accelerator mass spectrometry (AMS) dating. Geophysical testing was hampered by several factors, including complex sediments affected by modern drainage. New information was obtained, however, on the composition, age, and spatial distribution of the wooden fishing structures preserved in peat over 5000 years.     

An Assessment of the Role of an Open Shelter in Reducing Soiling and Microbial Growth on the Archaeological Site of the Bishop’s Palace,Witney, England

Two sets of twelve Portland limestone tablets were attached to carousels outside and under the open, lightweight shelter at Bishop’s Palace (Witney, England) for 18 months to assess the influence of shelters on soiling and microbiological growth on stone. At the start, and at 6-month intervals, tablets were analysed using microscopy (optical and SEM), colour measurement (spectrophotometry), weight change measurement and salt content determination (ion chromatography). Concentrations of NO₂ and SO₂ were also monitored for a month using diffusion tubes. In addition, results were compared with those obtained by the UK National Materials Exposure Programme (NMEP) on chemical weathering rates. Differences in soiling and biological growth on sheltered and unsheltered samples, and their influence on limestone decay were established. The shelter is likely to reduce biological growth by modifying the micro-environmental conditions. However, it may also exacerbate dust deposition, which might increase decay rates in the long-term.     

A Spanish Man‐o‐War in New Zealand? The 1864 wreck of Grafton and its lessons for pre‐Cook shipwreck claims

This paper considers the 1864 wreck of Grafton in the Auckland Islands, and its implications for wreck analysis and pre‐Cook exploration claims. The captain of Grafton, Thomas Musgrave, stated that the schooner was built from the wreck of a Spanish man‐o‐war, and archaeological analysis of the wreck found that the timbers are a tropical South American species, and had possibly been reused. The implications of this are clear; it is possible that timbers that originated in pre‐Cook (1769) ships lie in New Zealand, but without a full understanding of the historical and archaeological context of any such timbers, including their reuse in later ships, it is not possible to claim proof of pre‐Cook European exploration of New Zealand.     

The in situ preservation of archaeological remains: using lysimeters to assess the impacts of saturation and seasonality

Recent research has studied the effects of seasonal variability on waterlogged burial environments. In a new approach to the study of archaeological contexts, the use of controlled laboratory conditions via lysimeters has enabled new insights into the nature of short term fluctuations in saturation, and the impact that these can have on burial contexts. In addition, the protocols used have facilitated interesting insights into burial environments and the way in which fluctuations in saturation and seasonality can impact on the contained organic components within them.     

Calculus,periodontal disease and tooth decay among the prehispanic population from Gran Canaria

In the prehispanic Gran Canaria there are some anthropological differences between the coastal inhabitants who buried their dead mainly in tumuli, and those from the central mountains, mainly buried in caves. Some data, as the prevalence of auricular exostoses, and a different bone Ba/Sr ratio support the view that there were differences in economy and diet between both groups of islanders. Moreover, the proportion of carious teeth was significantly higher among the population buried in caves. In the present study we analysed the prevalence of dental calculus, periodontal disease and antemortem tooth loss in remains of 791 individuals belonging to the anthropological collection of the Museo Canario (Las Palmas). Calculus deposition was very frequent (88.51%), no differences existing between men and women or between those interred in tumuli or in caves. Age at death was the only parameter independently related to calculus deposition by stepwise multivariate analysis. Periodontal disease was observed in 66.78% of the population, significantly more in men (χ² = 4.88, P = 0.027). No differences existed between individuals buried in tumuli and in caves. Antemortem teeth loss was observed in 64.73% of individuals, no differences existing between men and women or between those interred in tumuli or in caves. There was a significant association between calculus and periodontal disease (χ² = 18.07, P < 0.0001). Both caries (χ² = 8.40, P = 0.004) and periodontal disease (χ² = 44.96, P < 0.0001) were associated with tooth decay. However, the proportion of teeth with calculus deposition (in relation to observed teeth) was significantly higher among the population buried in tumuli (Z = 3.18, P = 0.001), although no differences were observed when the proportion of antemortem lost teeth and alveoli with periodontal disease were compared among people buried in tumuli and in caves, but women showed significantly lower proportions of alveoli with periodontal disease and antemortem tooth decay. These data suggest that the population buried in caves had a different dietary pattern to that of those buried in tumuli, since calculus deposition -more frequent in the latter-may be related to the consumption of proteins. The results also point to the existence of differences in diet between men and women.     

内蒙古赤峰市大山前第一地点夏家店下层文化的植被和生态气候

内蒙古赤峰市大山前遗址属于中国北方青铜时代早期文化遗存 ,出土了大量夏家店下层文化遗物 ,其年代为 2 0 0 0BC～ 15 0 0BC。本文对大山前第一地点 1996年发掘区中部的探方T4 0 6内F8H1灰坑出土的木炭碎块进行了种属鉴定 ,并对出土的不同树种的木炭碎块进行分类和称量 ,得知当时的地带性植被为油松林和蒙古栎林 ,生态气候为温湿类型 ,同时也存在着气候暖干波动现象 ;柳属的发现说明遗址附近有河流存在 ;根据蒙古栎的起源和生态特性推测这一时期可能有人类的砍伐活动 ;H1出土的油松木炭可能绝大多数属于薪炭遗存     

First Trials to Set Up a Microwave Reflectometric Tool for the Survey of Historic Timber Structures

Timber structures can be degraded during their life both by structural problems and by biological degradation factors like fungi and insects. The occurrence of those biodegradation agents could lead to a loss of their structural integrity, in the absence of appropriate maintenance. An early assessment of the decay is even more important when the wooden structures are part of historical buildings, in the interest of conservation of cultural heritage.

This article presents an application of microwave reflectometry for the in situ evaluation of timber structures. The measurement system allows detecting anomalies inside the material in a non-destructive and non-invasive manner.

The reflection coefficient is measured by means of a vector network analyzer (VNA) using a double-ridge antenna which transmits the continuous-wave (CW) microwave signal and receives the signal reflected by the material under investigation.

Measurements on laboratory models demonstrated the feasibility of the method. Results obtained on timber beam sections, compared with the findings of traditional investigation methodologies, demonstrate the potentiality of microwave reflectometry, suggesting its possible usefulness during the diagnostic phase as a non-invasive tool for preliminary screening.