A simple Bayesian approach to tree‐ring dating

Tree‐ring dating involves matching sequences of ring widths from undated timbers to dated sequences known as ‘master’ chronologies. Conventionally, the undated timbers (from a building or woodland) are sequentially matched against one another, using t‐tests to identify the relative offsets with the ‘best’ match, thus producing a ’site’ chronology. A date estimate is obtained when this is matched to a local master chronology of known calendar age. Many tree‐ring sequences in the UK produce rather low t‐values and are thus declared not to have a ‘best’ match to a master chronology. Motivated by this and the routine use of Bayesian statistical methods to provide a probabilistic approach to radiocarbon dating, this paper investigates the practicality of Bayesian dendrochronology. We explore a previously published model for the relationship between ring widths and the underlying climatic signal, implementing it within the Bayesian framework via a simulation‐based approach. Probabilities for a match at each offset are produced, removing the need to identify a single ‘best’ match. The Bayesian model proves successful at matching in both simulated and real examples.     

Locating the origins of wood resources: a review of dendroprovenancing

Dendroprovenancing studies have been shown to have historically been initiated on the use of oak in art-historical contexts, but are now employed on a much wider range of species and artefact types, particularly in relation to ship remains. The commonest methodology is to compare individual site chronologies with a network of other chronologies, and to recognise trends in the geographical distribution of strong matches, suggesting the likely source area of the material. Other studies may look at the matching of individual timbers to draw similar conclusions. It is shown that ecological and genetic factors may strongly influence individual matching results and that ring-widths may therefore be considered a somewhat crude means of provenancing. Additional chemical and genetic markers are discussed, although these are unlikely to become routinely used in the near future.     

Tree‐Rings,Timbers and Trees: a dendrochronological survey of the 14th‐century cog,Doel 1

In 2000, the remains of a cog, Doel 1, were found in Doel, Belgium. Wood species identification of all ship timbers and smaller elements was performed. European oak was the dominant species, followed by alder that was used for the fairings. In total 150 ring‐width series were recorded. The construction date was set at AD 1325/26 and the timbers proved to originate from forests along the rivers Elbe and Weser. For the bottom strakes a strict symmetrical layout was observed. The keel plank was hewn from a trunk with a slightly earlier felling date. Repairs were performed with high‐quality boards, some with a southern Baltic provenance.     

Medieval Britain in 1980

THIS PAPER briefly outlines earlier work in southern England and discusses particular problems associated with the tree-ring dating of building timbers in the region. Specific examples from recent research not only highlight these problems, but show the success that may also be achieved. A new regional chronology for southern England, constructed entirely from building timbers, is presented and its use and further development discussed.     

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.     

An English Tree-Ring Chronology,A.D. 404–1216

AN 813-YEAR OAK CHRONOLOGY, A.D. 404–1216, is presented. Its construction has taken three years because of the difficulty of finding suitable Saxon timbers and the need to test the reliability of the dating. Although based on only a few timbers for the period c. A.D. 700, it can be used to date Saxon and medieval timbers whilst more material is found to consolidate that section of the chronology.     

Tree-ring chronologies for the 6th to 16th centuries for oaks of southern and eastern England

The background to the problem of providing useful oak chronologies for the variable environmental conditions that apply in southern and eastern England is outlined. The reference chronologies published here embrace three new principles. Firstly, the samples, nearly 300, on which they are based are almost entirely of boards or planks that are of radial section (from oaks aged on average about 250 years) that form part of panel paintings or chests. Secondly, to take account of the differences in the growth pattern with the vigour of growth, separate chronologies for sequences of different ring-width have been formed. Thirdly, on account of the difficulties in extending, with the samples available, an English chronology by the method of overlapping, eight separate chronologies, each about 300 years long, have been created. Matching has been based on German methods, i.e. computer comparisons (with more than one reference chronology) supported by visual comparison of charts. Agreement values in about half a million positions were calculated.These reference chronologies, expressed as ring-widths, are suitable for application to oaks that have grown within a region of considerable size that covers both sides of the North Sea. For panels used as a support for paintings of the 15th and 16th centuries, they have dated 85% of 130 English (London area) ones and about the same percentage of 25 Flemish ones. Rather earlier, sequences for oak boards used in places as far apart as York, Norwich, Oxford and Winchester have been matched. In the 10th to 12th centuries, the ring-width chronology derived for the London area shows good agreement with those for the hilly regions of Germany and that for Schleswig, as well as dating floor planks from Viking houses in York. A floating chronology, 322 years long, dataed to the 6th to 9th centuries by several radiocarbon analyses, has been formed from long sequences of rings from timbers excavated at Old Windsor and Portchester: this has matched material from Southampton and is linked with a mean curve for the well at North Elmham (Norfolk) and the strakes of the Graveney ship.     

The Marausa Wreck,Sicily: interim report on a boat built in the Western Imperial Roman tradition

In 1991, the wreck of a late 3rd–early 4th century AD Roman merchant vessel was discovered on the west coast of Sicily that had carried North African amphora, tubuli, and other ceramics. The hull was dismantled and raised in 2011, including a keel hook‐scarfed to stem and sternposts, 39 pegged mortise‐and‐tenon joined planks, 43 frames with an irregular pattern of floor‐timbers, half‐timbers, and futtocks fastened to the planking with treenails and copper nails, sister‐keelsons and evidence of two stringers, 36 ceiling strakes, and the base of a bilge pump. Many repairs are indicated. The fairly flat bottom and round bilges, mortise‐and‐tenons, sister‐keelsons and lack of a coherent framing pattern, place the boat in the Western Imperial tradition.     

A SCIENTIFIC INVESTIGATION ON THE PROVENANCE AND TECHNOLOGY OF A BLACK‐FIGURE AMPHORA ATTRIBUTED TO THE PRIAM GROUP*

The restoration of a Greek black‐figure amphora provided an opportunity to study the provenance and production technology of the vase. The composition of the ceramic body, determined by inductively coupled plasma optical emission spectroscopy (ICP–OES), matches that of Attic products. Investigation by X‐ray diffraction and reflectance spectroscopy suggests a maximum firing temperature around 900°C and a body re‐oxidation temperature around 800°C, respectively. The morphology and composition of black, red and dark red surface areas were studied by scanning electron microscopy and X‐ray energy‐dispersive analysis; the black areas show the features of a typical well‐vitrified black gloss, while the red areas were most probably obtained by simple burnishing of the body; the dark red additions, on the other hand, are the likely result of a partial re‐oxidation of a clay–ochre mixture.     

RELIABILITY AND REPEATABILITY IN DENDROCHRONOLOGICAL ANALYSIS: TESTS USING THE FLETCHER ARCHIVE OF PANEL-PAINTING DATA

Research into the dates of timber used for art-historical objects has provided a large data set on which to test standard dendrochronological techniques. Some 177 sets of tree-ring measurements, originally analysed by the late Dr J. M. Fletcher at Oxford University, have been re-examined independently in the tree-ring laboratories at the University of Sheffield and the Museum of London Archaeology Service. The results show a high level of agreement between the laboratories. In contrast, many of the dates produced by Dr Fletcher for the paintings are not confirmed. The two different approaches described here also resulted in remarkably similar internal groupings of the dated material. These groupings probably reflect the provenance of the timbers and suggest that two different areas of the eastern Baltic supplied the bulk of the material with smaller quantities of panels originating in Britain and central Europe.     

Dendrochronological Dating and Provenancing of Timbers from the Arade 1 Shipwreck,Portugal

As part of a larger project promoting the development of historical dendrochronology in the Iberian Peninsula, ship‐timbers from the Arade 1 wreck (mostly planking and framing elements), stored at the DANS/IGESPAR in Lisbon, were examined. Of these, 52 samples were identified as deciduous oak (Quercus subg. quercus) and two as chestnut (Castanea sativa). Of 24 timbers selected for dendrochronological research, 23 could be dated, placing the origin of the wood in western France and the felling of trees between AD 1579 and 1583. Their homogeneity suggests they are part of the original construction, which probably took place shortly after AD 1583. © 2012 The Authors     

AN EPR AND ISOTOPIC STUDY OF THE MARBLES OF THE TRAJAN's ARCH AT ANCONA: AN EXAMPLE OF ALLEGED HYMETTIAN PROVENANCE*

The provenance of 20 marble samples drawn from the Trajan's arch at Ancona, which is supposed to be made of Greek, Hymettian marble, has been established on the basis of the independent use of EPR and isotopic data. The results of the two methods are in good agreement and unequivocally indicate a Proconnesian provenance. Sixteen samples are assigned to this site, whereas two are classified as untypical Proconnesian samples and the remaining two are assigned an unlikely Parian provenance. No indication exists for a possible Hymettian origin of the marbles. A multi‐method approach, which employs all of the experimental variables simultaneously, demonstrates that the 18 samples identified as Proconnesian belong to several different quarrying areas within the site. This result is taken as an indication that the Proconnesian quarries were run following a highly organized, semi‐industrial production model. The origin of the Hymettian/Proconnesian misunderstanding and the possible misclassification of other Roman monuments in Italy are briefly commented on.     

Some thoughts on art-historical dendrochronology

Imported timbers pose potential problems for the dendrochronologist. The problem is general and any particular dendrochronologist may run into difficulty when he attempts to correlate an exotic ring pattern against an indigenous chronology. Sufficient evidence exists to suspect that high quality oak boards and planks were extensively imported into England in medieval times. However, chronologies constructed from just such boards, namely the art-historical chronologies, have been treated as indigenous without being proven to be so. Almost identical comments can be made with respect to art-historical chronologies constructed by German workers using supposedly indigenous Flemish oak panels. This article explores how failure to allow for importation may well call into question the dating of these art-historical chronologies and in addition demonstrates how an art-historical dating system has been created wherein erroneous placement of the chronologies could escape detection (this latter aspect may well make the argument of general interest to scientists).     

BLACK AND RED GRANITES IN THE EGYPTIAN ANTIQUITY MUSEUM OF TURIN: A MINERO‐PETROGRAPHIC AND PROVENANCE STUDY

A recent project to investigate the stone artefacts preserved in the Egyptian Antiquity Museum of Turin has been undertaken, with the aim of supplying their systematic classification and suggesting the provenance site of the original raw materials. This paper focuses on seven sculptures dating back to the New Kingdom (18th–19th Dynasties): the statue of Ramses II, three of the 21 sculptures of the goddess Sekhmet, the statue of the goddess Hathor, the Ram‐headed Sphinx and the sarcophagus lid of Nefertari. Petrographic observations have shown that all the sculptures are made of granitoid rocks, with variable composition from granite to granodiorite and tonalite. The observation of strong macroscopic analogies with the so‐called black and red granites outcropping in the Aswan area has suggested a common origin of all the raw materials used for their manufacture. In order to verify this provenance hypothesis, several samples were collected in the Aswan quarry districts. According to results of a minero‐petrographic and geochemical comparison between the statues and the Aswan quarry samples, it was possible to identify the source area of the stone sculptures and finally to highlight the importance of an archaeometric approach to the solution of archaeological problems.     

ARCHAEOLOGICAL AMBERS FROM NORTHERN ITALY: AN FTIR–DRIFT STUDY OF PROVENANCE BY COMPARISON WITH THE GEOLOGICAL AMBER DATABASE*

European geological ambers of five different localities and types, and Italian geological ambers from seven different deposits have been studied with Fourier transform infrared spectroscopy (FTIR) and diffuse‐reflectance infrared Fourier transform (DRIFT). Ambers from several localities have been characterized for the first time. The research aims to create a database of European ambers, containing both FTIR and DRIFT data. The FTIR spectra are easily comparable with the data commonly available in the literature, whereas DRIFT analyses are shown to be more useful to characterize the archaeological finds. The provenance of several archaeological ambers from northern and southern Italy, dating from the Middle Bronze Age to the Iron Age, is assessed on the basis of the developed database. Of the 35 analysed archaeological objects, all but five are composed of Baltic succinite amber.     

The 7th–9th Century Tantura E Shipwreck,Israel: construction and reconstruction

The Tantura E shipwreck was discovered in Tantura lagoon, Israel, in a water depth of 2.8 m, covered by 1 m of sand. It was a coaster that plied the Levant coast, dated to the 7th–9th centuries CE. It was recorded under water, but several components were studied on land, as well as the finds. The hull is of frame‐based construction, with flat floor timbers and a sharp turn of the bilge. The archaeological evidence, as well as modern design tools and regulations, suggests that Tantura E was c.12.5 m long, of 25 tonnes displacement, and could load c.17.5 tonnes.     

故宫武英殿建筑群木构件树种及其配置研究

我们从武英殿建筑群的武英门、武英殿、敬思殿、武英门东西值房、东配殿及北值房、西配殿及北值房、恒寿斋、井亭11座建筑的20余种木构件上,共采集1145个样本进行树种鉴定。结果表明,武英殿建筑群共使用了15个种或属的木材,其中有落叶松、软木松、硬木松、冷杉、云杉、黄杉、柏木、杉木、圆柏、金钱松等10种针叶材,桢楠、椴树、润楠、喃喃果、印茄等5种阔叶材。其中,杉木、桢楠和润楠是我国南方树种,喃喃果和印茄是东南亚进口材。武英殿主要承重木构件选用主要为北方树种中密度和力学强度较高的落叶松、黄杉和云杉,其他木构件则主要使用的是密度低、重量轻的软木松;敬思殿主要承重木构件使用的是云杉,其他木构件也以软木松为主,但使用的木材比较杂,角梁和爬梁全部使用了东南亚进口阔叶材;敬思殿在选材方面与武英殿的差异,可能是在光绪三十年重建时选材标准不如武英殿严格所致。武英门的木材,硬木松占了绝大多数,使用的都是强度较大的木材。所有配殿和值房的主要承重构件中,柱使用最多的是硬木松,其次是落叶松、软木松;月梁、三架梁和四架梁、瓜柱、四架梁随梁、抱头梁及其随梁木构件使用的是杉木,配殿、值房等建筑的梁没有使用强度高的木材。是以南方树种为主,其中某些主要构件还使用了珍贵的南方阔叶树种如桢楠、润楠等。这种情况表明,恒寿斋和井亭是武英殿几次大火后的仅存建筑,因而保留了明代建造时选材的历史信息。木材的使用差异具有一定的时代意义。从润楠在恒寿斋的柱和梁上,椴树、桢楠和润楠在斗棋上使用,以及根据构件的承重和位置不同进行树种配置,既考虑了对主要建筑结构材的强度要求,也考虑了尽可能减小其他木构件对主要构件的负荷,这种按照木材物理力学的性质和木材承重强度等因素进行选材的建筑原则,相当清楚地表明当时吉建筑在科学选材方面已达到很高的水平。在故宫维修工程中通过对各种木构件树种配置的研究,进行科学定性分析,将深层次地探索古建筑留给我们的历史痕迹和信息,揭示其科学性,为制定维修保护方案提供科学依据,并为故宫古建筑保护研究提供新的方法,丰富故宫历史档案资料。     

NON‐DESTRUCTIVE ANALYTIC METHOD USING XRF FOR DETERMINATION OF PROVENANCE OF ARCHAEOLOGICAL OBSIDIANS FROM THE MEDITERRANEAN AREA: A COMPARISON WITH TRADITIONAL XRF METHODS*

A non‐destructive analytical method using wavelength‐dispersive X‐ray fluorescence (WDXRF) that allows the establishment of the provenance of archaeological obsidians was developed and a comparison with the classical XRF method on powders is discussed. Representative obsidian samples of all the geological outcrops of archaeological interest of the Mediterranean area (Lipari, Pantelleria, Sardinia, Palmarola and the Greek islands of Melos and Gyali), were analysed with the normal procedures used in rock analysis by XRF (crushing, powdering and pelletizing). The non‐destructive XRF analysis was instead conducted on splinters taken from the original geological pieces, with the shape deliberately worked to be similar to the refuse usually found at archaeological sites. Since the analysis was conducted on the raw geological fragment, intensity ratios of the suitably selected chemical elements were used, instead of their absolute concentrations, to avoid surface effects due to the irregular shape. The comparison between concentration ratios (obtained by traditional XRF methods) and the intensity ratios of the selected trace elements (obtained from the non‐destructive methodology) show that the different domains of the chemical composition, corresponding to the geological obsidians of the source areas, are perfectly equivalent. In the same way, together with the geological splinters, complete archaeological obsidians, from Neolithic sites, may be analysed and their provenance may be determined. The proposed non‐destructive method uses the XRF method. Due to its sensitivity, low cost and high speed, it is surely an extremely valid instrument for the attribution of the provenance of the archaeological obsidian from Neolithic sites.     

The Potential of Tree Rings in Eucalyptus pauciflora for Climatological and Hydrological Reconstruction

We investigate the causes of variability in a tree‐ring chronology comprising data from Eucalyptus pauciflora Sieb. Ex. Spreng. at the alpine treeline on the Kosciuszko Plateau in New South Wales, Australia. Following verification of crossdating in a subset of the available data, we found that ring width correlates significantly with net radiation, precipitation and mean minimum and maximum air temperature during the preceding winter and spring of the growing season. Our results for spring are consistent with the impact of climate on tree growth in alpine woodlands reported in previous studies. Analyses of snow‐depth data revealed negative correlations with ring width throughout winter and spring. Our results indicate that low temperature and high precipitation during winter negatively affect the growth of E. pauciflora by prolonging spring snow cover. Ring width also correlates significantly with an index of soil dryness and flow in rivers with their headwaters in the Kosciuszko plateau. Given the apparent sensitivity of our chronology to climate and snow conditions, our results suggest that tree‐ring chronologies comprising data from E. pauciflora at the alpine treeline have potential for climatological and hydrological reconstruction in southeast Australia.     

Provenancing Baltic timber from art historical objects: success and limitations

During the Middle Ages northern Belgium and The Netherlands were gradually deforested. A steadily rising demand for quality timber obliged merchants to look for new timber sources. From the 13th century onwards, large volumes of timber were imported from surrounding regions and, despite the remote supply area, merchants of the Hanseatic League managed to organize a huge timber trade from towns around the Baltic Sea.Trees from forests along the Vistula River seem to have been exported via Gdansk, first to Bruges and later to Antwerp. At their final destination the imported wood assortments were highly appreciated for shipbuilding and construction purposes, but also by woodcarvers and famous painters.Over the last decade dendrochronologists have established a dense network of historical site chronologies for northern and central Poland. These site chronologies are supposed to reflect local growth conditions and may allow the identification of the provenance of the wood of many art historical objects made out of Baltic timber.Tree-ring patterns of panel paintings and sculptures, mainly from the 14th–16th centuries, were measured and compared to this data set of site chronologies. An evaluation of the accuracy of sourcing medieval Baltic timbers using standard correlation techniques was made. The identification of provenance enriches historical information on logging activity and timber trade around the Baltic Sea during the Middle Ages.