A STATISTICAL APPROACH TO THE CALIBRATION OF FLOATING TREE-RING CHRONOLOGIES USING RADIOCARBON DATES

The bristlecone pine tree-ring calibration of radiocarbon dates, while necessitating changes of up to 700 years in Holocene chronology before 1000 b.c. , offers possibilities of very accurate dating when ¹⁴C determinations from floating tree-ring chronologies are utilized. A statistical approach assuming linear regression is developed and used to position the floating tree-ring chronologies at Swiss neolithic sites, using radiocarbon dates published by Ferguson, Huber and Suess and by Suess. The statistical method gives objective estimated dates with estimates of error related, in a consistent and explicit manner, to the inherent inaccuracies of the radiocarbon dates. Most of the method may readily be tested by standard statistical procedures. For the particular cases considered the assumptions of linearity and parallelism are investigated, and the precision of the estimated dates is comparable with that claimed by Suess and his co-workers. A precise calibration is thus possible without utilizing the short-term fluctuations in the Suess calibration curve. The analysis, while avoiding some assumptions of Suess and his collaborators, offers an explicit procedure for establishing controlled teleconnections with the Ferguson dendrochronology, and supports their emphasis on the importance of radiocarbon dates from floating tree-ring sequences for the construction of precise prehistoric chronologies.     

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).     

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.     

PROBLEMS OF THE RADIOCARBON CALENDAR AND ITS CALIBRATION

Both the growing body of literature on the tree-ring calibration of radiocarbon dates, and the variety of statistical approaches used, make it appropriate to review the basic principles involved in the construction of a calibration curve. While its ultimate validity is in part a geophysical problem, the appropriate form for the calibration function, given a specific body of data, is a statistical question centering upon the analysis of the measurement errors involved. The relationship between the calibration function and the inverse calibration function is examined, and the shortcomings of the available published calibration curves considered in the light of this examination. It is concluded that there is no reason to doubt the general principles on which the calibration is based, but a need exists for a more critical handling of the measurement data with a statistical treatment of the errors involved. The quality of the data could itself be improved by the use of replicate samples for inter-laboratory projects specifically designed to investigate the magnitude of measurement error.     

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.     

Radiocarbon dating of marine shell samples. The marine radiocarbon reservoir effect of coastal waters off Atlantic Iberia during Late Neolithic and Chalcolithic Periods

Radiocarbon dates on marine shells have not been used as extensively as charcoal or bone dates for the setting up of absolute chronologies because interpreting these dates is complicated by the marine radiocarbon reservoir effect. Nevertheless marine shellfish were used widely at least during the Holocene and their shells are abundant and usually well preserved in archaeological deposits located near shorelines. Consequently prior research concerning the oceanographic conditions and the marine radiocarbon reservoir effect of a particular coastal area is needed in order to set up reliable chronologies for that region. Values of regional marine radiocarbon reservoir effect – ΔR – of coastal waters off Atlantic Iberia, some of its variability along the Holocene and its correlation with the upwelling phenomenon were determined during previous research. More data related to the ΔR values for western Portuguese coastal waters during the Late Neolithic and the Chalcolithic, a time interval badly sampled in previous research, were recently obtained. These values can be compared with ΔR values already determined for the Gulf of Cadiz. Besides the importance of these values for a better knowledge of the palaeoceanography and palaeoclimatology of Atlantic Iberia, from now on archaeologists can set up reliable chronologies for Late Neolithic and Chalcolithic contexts using marine shell samples of that origin for radiocarbon dating.     

Sub-fossil wood from the Rucianka raised bog (NE Poland) as an indicator of climatic changes in the first millennium BC

The dendrochronological studies were carried out on very well preserved sub-fossil pine wood found in the biogenic deposits of the Rucianka raised bog (NE Poland). Local floating chronologies, covering the period 990-460 cal BC, were dated on the basis of radiocarbon analyses. Growth depressions in annual treering widths indicated periodical deterioration of the environmental conditions, which affected tree growth. Identified germination and dying-off phases (GDO) should be related to the wetter climatic periods. The extinction of trees took place during periods of higher groundwater level which, in turn, caused favourable conditions for growth of young pines.     

江苏省流动人口分布的格局演变及其驱动因素——基于城乡建设用地的探讨

基于乡镇单元人口普查数据以及相应年份的城乡建设用地数据,运用空间分析和统计分析方法,尝试分析城镇-农村尺度江苏省流动人口分布格局的时空演变特征,并揭示驱动人口流动的动力机制。结果表明：①规模分布特征是具有较长大值右尾部的正偏分布,总体的集聚趋势增强,城镇和乡村集聚流动人口差距变大;②空间呈现高值集聚特征,热点区主要集中在长江以南的城镇,沿江地区流动人口高密度区域逐渐连绵化;③增长变化呈现长江以北地区城镇的流入人口增加、农村的输出人口减少,以及长江以南地区城镇的流入人口快速增加、农村的流入人口普遍增加的特征;④经济发展水平差异、乡镇企业繁荣、交通可达和政策导向是影响江苏省流动人口集聚的四大动力。     

大城市外围地区流动人口结构及其城镇建设用地使用特征研究——以深圳市平湖镇为例

文章以深圳市平湖镇为例,通过实地考察和典型调查,对大城市外围地区流动人口的结构及其城镇建设用地使用特征进行研究。发现平湖的流动人口结构较为简单,大多数是来自我国西南落后地区青壮年农村剩余劳动力,并且以务工和经商为主。由于其从业特征的差异,务工和经商人员分别集中在城镇工业区和商业区内,人口分布密度较高,人均建设用地面积严重偏低。文章认为在大城市外围地区的城市规划中必须加强对流动人口的用地需求研究,以解决大规模的流动人口与相对紧缺的城镇用地之间的矛盾,并且进一步做了平湖流动人口用地需求分析,提出其规划调整建议。     

Dating Historical Buildings: An Update on the Possibilities of Absolute Dating Methods

The reconstruction of the history of a building represents a difficult task, as written information is not usually available or incomplete. Some building materials (e.g., bricks, wood) have been classically used for absolute dating while on others has been considered unreliable (e.g., stone). However, developments and tests performed in the last 20 years have shown important advances on the use of such methods, increasing the possibilities of successful reconstruction of building chronologies, although most of these advances are still scarcely known by the community involved in the site management (e.g., archaeologists, architects). Both, radiocarbon and luminescence dating have been the most successful techniques but others, such as archaeomagnetism, can also be used. Even, some important events such as fires could be dated. The purpose of this work is to provide an overview of the last achievements of absolute dating techniques available in building materials.     

A lake fortress,a floating chronology,and an atmospheric anomaly: the surprising results of a radiocarbon wiggle-match from Āraiši,Latvia

An Iron Age timber settlement which, in view of the defensive structures uncovered, is described as a lake fortress, on an island in Lake ārai?i, north-eastern Latvia, was excavated in 1965–69 and 1975–79 by teams led by Jānis Apals, who distinguished five construction phases. Dendrochronological analysis produced a c. 100-year floating chronology for Norway spruce (Picea abies (L.) Karst.) timbers from the earliest phase. A ¹⁴C wiggle-match was undertaken to obtain an absolute date range for the final year of the floating chronology, and thus for the construction of the settlement. Ten blocks of wood from one timber, each comprising 6-11 years and collectively spanning the whole 93-year tree-ring series, were dated by AMS. Using the IntCal13 calibration data, there is a 95% probability that the felling date of this timber falls in the range 775–784 cal AD. It appears, however, that the AD 775 spike in the atmospheric ¹⁴C level occurred within the 6-year span of the last sample. On this basis, we can narrow the date of construction to 776–780 cal AD. This date is significantly earlier than those reported in previous publications.     

福建省城镇流动人口的空间分异格局——基于六普数据的分析

文章基于第六次人口普查数据,运用数理统计、空间自相关和GIS等方法,分析了福建省城镇流动人口的空间分异格局。研究发现,福建省城镇流动人口在沿海多而密集、以区外流动为主,开放性和活跃性明显,而在内陆则少而稀疏、以区内流动为主,封闭性和粘滞性突出,但沿海和内陆均存在内部异质性;大城市流动人口密集且来源地广泛、对人口城镇化影响大,中等城市流动人口规模较小,小城镇对区内流动人口有一定吸纳能力。文章还探讨了城镇流动人口空间分异特征的驱动机制、对区域社会经济发展和城镇化的影响,并提出相关政策建议。     

Bayesian Estimation of Regional Production for CGE Modeling

Abstract Computable general equilibrium (CGE) models are often criticized for using restrictive functional forms and relying on external sources for parameter values in their calibration. CGE modelers argue that in many instances reliable econometric estimates of important model parameters are unavailable because they must be estimated using small numbers of time‐series observations. To address these criticisms, this paper uses a Bayesian approach to estimate the parameters of a translog production function in a regional computable general equilibrium model. Using priors from more reliable national estimates, and parameter restrictions required by neoclassical production theory, estimation is done by Markov chain Monte Carlo simulation. A stylized regional CGE model is then used to contrast policy responses of a Cobb‐Douglas specification with those from the estimated translog equation.     

Radiocarbon dating and the “old wood” problem: The case of the Hohokam chronology

Many archaeological chronologies, including that of the Hohokam in southern Arizona, are based on a series of radiocarbon dates on wood. This paper argues that because of variability in rates of wood decay processes (in the environment and in systemic context), such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed. Following the theoretical insights of Dean (1978), this paper sets forth principles and procedures for relating radiocarbon dates to cultural events. Emphasis is placed on identifying and taking into account the formation processes of (1) the dated specimens and (2) the deposits that yielded them. This methodological framework is applied to Hohokam radiocarbon dates, and a chronology much shorter than the original Gladwin-Haury formulation is supported.     

Radiocarbon and dendrochronological dating of Sub-fossil oaks from Smarhoń riverine sediments

Sub-fossil oaks from Smarhoń in Belarus have been investigated and tree-ring chronologies were assembled. According to radiocarbon dating, the oldest oak grew from 5782–5612 cal BC and the youngest from 1575–1747 cal AD. Radiocarbon and dendrochronological dating of 97 samples, four single series, 10 mean curves (containing 2–9 series) and three chronologies (10–25 series) were constructed. The longest chronology (No. 16), covering 549 years, was absolutely dated against various oak chronologies of Polish/Baltic origin to AD 778–1326. Germination and dying-off phases were assessed from the three best replicated chronologies. A spectral analysis of the chronologies provided cycles of variable length, on average of 25 years.     

GAUSSIAN CURVES FOR VISUALIZING CHRONOLOGICAL PATTERNS OF CERAMIC FINDS AND RESIDUALITY*

This paper describes a particular statistical approach to chronological data from assemblages of archaeological finds (namely pottery) using Gaussian curves: the method enables us to obtain a graphic representation of chronological patterns that avoids an excessive flattening of data, adding an extra dimension to the usual linear temporal concepts. This enables us to arrive at more likely absolute dating and also visualize residuality. The method has been built during the study of a stratigraphic context from the Site of Ancient Ships of Pisa – San Rossore, Italy, and applied to its pottery. Archaeologists may find in the model a useful tool that is easy to apply.     

Iberian Dendrochronology and the Newport Medieval Ship

At the time of the discovery of the Newport medieval ship, it proved impossible to date the timbers used in its original construction through dendrochronology. Associated British timbers and artefacts provided dating to the mid 15th century, with the latter pointing to strong Iberian connections. The development of regional oak ring‐width chronologies in the Basque Country, and their extension back in time to overlap with the ring‐width mean developed for the Newport Ship, has allowed absolute dating and provenance of timbers used in its original construction. Further research is required to clarify the geographical source of the timbers and to develop a high‐resolution network of tree‐ring data for the region.     

Dendrochronological dating of wooden artifacts by measuring the tree rings using magnifying glass and photography-assisted method: an example of a Dutch panel painting

Dendrochronology, an analysis of tree rings, is a commonly used method for dating wooden structures in archaeological remains and historical objects. Fascinating subjects of examination are the historical oil paintings on oak panels. Here, we applied a tree ring analysis on three boards of a Dutch painting from the Sinebrychoff Art Museum (Helsinki). Tree rings were measured using the conventional lens-assisted method, in addition to the photography-based approach, where the widths of the rings were determined from digital enlargements of the photos. These two methods produced comparable tree ring series. The lens- and photography-based records of the measured panel exhibited higher agreement with each other than the conventional, lens-based, record against the different master chronologies. Dendrochronological cross-dating against the master chronology showed that the rings of the panel represent the period ad 1413–1620. Cross-dating was attained by comparing the tree ring series of the panel painting with the previously published chronologies obtained from timber transported from the historical ports of the Eastern Baltic Sea to Western Europe. Photography appears as a promising method to be used for dendrochronological investigations of archaeological and historical objects, alongside the conventional methods. We note that the importance of using photographs of tree ring cross sections was highlighted already in the 1930s. In the digital era, the photographic approach shows obvious benefits for archival purposes and remeasuring the rings, with additional future prospects of image processing and analyses.     

Resource Exploitation and Wood Mobility in Northern European Oak: dendroprovenancing of individual timbers from the Mary Rose (1510/11–1545)

Dendrochronology has proved useful in suggesting the provenance of timbers in northern Europe, particularly for ship‐timbers, which may have originated from a distant source. Historical chronologies are usually derived from timbers of uncertain origin. In trying to provenance a new chronology, therefore, trends in the geographical distribution of statistical matches should be viewed, rather than individual strong matches. While it is usual to test a site‐chronology created from several individual timbers, in a situation such as the Mary Rose, where individual timbers may have been sourced from several regions, the matches of individual timbers may shed light on their origins. © 2010 The Author     

Fluvial sediments, correlations and palaeoenvironmental reconstruction: The development of robust radiocarbon chronologies

Multiple sequences of radiocarbon dates extracted from organic materials are increasingly being used to provide robust chronologies for landscape development, particularly the timing and correlation of significant climatic and ‘process’ events. Whilst the validity of using such frameworks in sedimentary environments such as lake basins and raised bogs has been the focus of much attention, such debates have not extended to fluvial systems. Using examples from three lowland, vertically accreting river valleys in East Anglia, UK, this paper assesses the robustness of their associated radiocarbon chronologies by assessing the contrasting age estimates that are obtained by dating different parts of the same organic sample (humic, humin and plant macrofossils) at a variety of stratigraphic levels. Overall, the humin and humic acid fraction results were statistically consistent, whilst the plant macrofossil remains were found to be of a slightly younger age. In these examples, it is argued that the younger ages appear to be the result of Phragmites (common reed) roots pushing plant macrossils through the sedimentary sequence or opening up voids for material to fall through, although studies in lacustrine and mire environments suggest alternative explanations may also be possible. Whichever explanation is preferred, this study demonstrates clearly that the complexity of valley floor stratigraphy and processes is such, that using single radiocarbon dates, whether AMS or bulk samples to reconstruct chronologies of ‘geomorphic system response’ may need to be refined and subjected to the same level of assessment that has been applied in other sedimentary systems.