Full‐Vector Archaeomagnetic Dating of a Medieval Limekiln at Pinilla Del Valle Site (Madrid,Spain)

Archaeomagnetic dating based on the full geomagnetic field vector was carried out on a limekiln excavated at Pinilla del Valle archaeological site (Madrid, Spain). The limekiln tradition in this area is largely documented by historical sources for recent centuries but the date of the studied kiln's last use was unknown. The combination of mean archaeomagnetic directional and absolute archaeointensity results shows that the kiln was last used between ad 1296 and 1413, in good agreement with two independent radiocarbon dates. This study provides the first archaeomagnetic evidence that the local limekiln tradition dates back to at least late medieval times. Furthermore, the inclusion of these data in the Iberian secular variation curve and geomagnetic field models will help to improve the archaeomagnetic dating technique.     

Archaeomagnetic dating of Dogmersfield Park brick kiln (Southern England)

Archaeomagnetic dating of samples from a brick kiln discovered at Dogmersfield Park has been achieved using both field direction and intensity. Detailed rock-magnetic properties and microwave archaeointensities have already been studied and published elsewhere [Ll. Casas, J. Shaw, M. Gich, J.A. Share, High-quality microwave archaeointensity determinations from an early 18th century brick kiln, Geophys. J. Int. 161 (2005) 653–661]. The archaeomagnetic measurements were assigned time-probability distributions by comparing with predictions from a global model at the sampling site, this procedure suppresses errors arising from relocation to a common central reference location. All three probability distributions consistently indicate the same age (∼AD 1700). Once the probability distributions are combined a narrower probability distribution is obtained, stressing the importance of pursuing combined (directional and intensity) archaeomagnetic analyses. The inferred age is also highly consistent with available historical evidence.     

RESEARCH REPORT: MAGNETIC INVESTIGATIONS AND THE AGE OF A MEDIEVAL KILN AT KUNGAHÄLLA (SOUTH‐WEST SWEDEN)*

The results from a magnetic survey and archaeomagnetic investigation of a medieval brick kiln at Kungahälla in Bohuslän (south‐west Sweden) are reported. Detailed magnetic total field and magnetic gradient measurements over known traces of the kiln showed marked local magnetic anomalies of up to 200 nT, revealing the rectangular shape of the kiln remains. Palaeomagnetic investigations of the remanent magnetization of 12 bricks from the kiln floor gave precise definitions of both the direction of the archaeomagnetic field [(D_m, I_m) = (66.7°, 8.8°), k = 655, α₉₅= 1.7°] and the palaeointensity [B_m= 69.0 ± 3.6 µT]. An archaeomagnetic date is obtained by comparing the direction of the archaeomagnetic field found in the kiln with a geocentral dipole‐transformation of the British master‐curve for secular variation. Of two possible archaeomagnetic dates (ad 1280 ± 50 or ad 1480 ± 50), the ad 1280 ± 50 age is in good accordance with the C‐14 ages and archaeological dates as well as with direct historical evidence, whereas a c. 100 years younger TL date appears to be too young.     

Archaeomagnetic versus luminescence methods: the case of an Early Byzantine ceramic workshop in Thessaloniki,Greece

In this contribution, we present a combined archaeomagnetic and luminescence study of archaeologically dated structures. The investigated area is a ceramic workshop comprising several Early Byzantine kilns. Based on (a) the archaeological–anthropogenic stratigraphy of the site, (b) the structural characteristics of the kilns and (c) the few ceramic findings revealed within their context, the operation of this brick and tile factory is approximately dated between the middle of the fifth century until the first decades of the sixth century AD. Three of the well-preserved workshop kilns have been studied archaeomagnetically. The full vector of the geomagnetic field, accompanied by rock magnetic analyses of the studied material, has been defined. The archaeomagnetic study revealed similar directions among the three kilns indicating and confirming their contemporary use. Additionally, several luminescence measurements were obtained on material from the same kilns. The dating of the site was performed with both methods. The archaeomagnetic dating is convergent with the archaeological estimation only when its upper limit is considered. Concerning the luminescence dating, the calculated ages (corrected for anomalous fading and for the ⁴⁰K content) with their standard deviations are convergent with the archaeological estimations for the first kiln, while for the other two, the results seem to be incompatible. The possible factors that provoked this divergence are thoroughly discussed.     

ARCHAEOMAGNETISM IN ARCHAEOMETRY— A SEMI‐CENTENNIAL REVIEW*

The journal Archaeometry and its first co‐editor Martin Aitken played key roles in the development of archaeomagnetism. This paper briefly reviews all papers published in Archaeometry, and a few others, dealing with archaeomagnetic secular variation, archaeomagnetic dating, archaeointensity studies and related applications of magnetic studies to archaeology, to indicate some of the major developments over the past 50 years.     

Archaeomagnetic data from three Punic sites in Tunisia

Archaeomagnetic analyses on bricks and slag fragments from kilns have been undertaken. Four new archaeomagnetic directions and two new archaeomagnetic intensities have been reported for three Punic sites in Tunisia. The SCHA.DIF.3K archaeomagnetic model gives the most consistent age estimates, in agreement with the archaeological ages for three of the four analyzed kilns. The archaeomagnetic models appeared to be surprisingly proficient both using archaeodirections and intensities for El Maklouba. The existence of kilns from different chronological archaeological phases (4th–3th century BC and 2nd–3rd century AD) has been confirmed for this site. The archaeological hypothesis that associates the kiln in El Gaala with the neighboring Punic necropolis is compatible with the archaeomagnetic data obtained from the kiln, though a modern use or remagnetisation of the kiln cannot be excluded.     

AN ARCHAEOMAGNETIC STUDY OF POTTERY KILNS FROM BRÜHL-PINGSDORF (GERMANY)*

Four pottery kilns from Brühl-Pingsdorf (Germany) were dated by comparing their characteristic remanent magnetization with a curve of the palaeo-secular variation of the geomagnetic field. Archaeomagnetic results suggest last heating events between AD 775 and 1020. The archaeological evidence generally supports the relative temporal succession and the duration of use, but indicates that the kilns are about 150 years younger on average. Hence, a systematic offset between these independently developed chronologies must be considered. Rock magnetic parameters display radial variations through the kiln walls. These variations are controlled by the maximum temperature the rock was exposed to. These parameters were used to identify specimen which acquired a thermoremanent magnetization.     

Salt production in pre-Funan Vietnam: archaeomagnetic reorientation of briquetage fragments

Bronze to Iron Age briquetage found in the northern Mekong Delta has an appearance similar to analogous material from Europe and Asia; however, the orientation in which the briquetage was employed during the production of salt is still under debate. As a consequence of the heating and subsequent cooling of the briquetage during the evaporative recovery of salt, the magnetic mineral particles within the ceramic formed a stable thermoremanent magnetization in alignment with the Earth's magnetic field. It thus becomes possible to find the orientation in which the ceramics were last fired by aligning their recorded archaeomagnetic signal with estimates of the Earth's ancient field direction in Vietnam. The archaeomagnetic directions obtained from 22 samples taken from five different briquetage artefacts are somewhat scattered, but they reveal a consistent orientation and thus the mode in which the briquetage was employed can be reconstructed.     

Archaeomagnetic dating of archaeological sites from Switzerland and Bulgaria

Baked materials from three archaeological sites in Switzerland and one in Bulgaria have been examined and dated archaeomagnetically. The detailed rock-magnetic properties of the burnt clay collected have already been studied therefore and have been published elsewhere (Geophysical Journal International 153 (2003) 146). The main aim of this paper is to determine the terminus ante quem for the last firing of the clay collected from pottery kilns or burnt layers. The directional and intensity results of the ancient geomagnetic field corresponding to the time of the structure's last firing are given for each site. These geomagnetic parameters are then compared with reference curves to provide archaeomagnetic dates for the last use of the kilns. Application of archaeomagnetism as a dating tool is only possible for those regions that already have reference curves. Bulgaria is fortunate in having established reference curves covering almost the last 8000 years. Two Swiss sites were dated using only directional results on the basis of existing palaeodirectional results for Switzerland as well as the French directional reference curves. The archaeomagnetic dates of three of the sites were then compared to archaeological evidence and available radiocarbon dates. The palaeointensity data obtained from this study will enrich the existing archaeomagnetic database for western Europe.     

A Stamford Ware Pottery Kiln in Pontefract: A Geographical Enigma and a Dating Dilemma

Abstract

THIS REPORT PRESENTS the results of analyses carried out following the discovery and excavation of a medieval pottery kiln in Pontefract, a discovery which featured in the ‘Fieldwork Highlights’ section of Medieval Archaeology 53 (2009). The kiln is remarkable for having produced vessels previously only associated with the Stamford ware industry of the late 11th and 12th centuries and demonstrates the existence of at least one northern production site, the likely existence of which was first mooted in the 1950s. As both radiocarbon and archaeomagnetic dating methods indicate a last firing of the Pontefract kiln in the late pre-Conquest period, the discovery also poses questions about the chronology of Stamford ware production.     

Archaeomagnetic research in the Andean highlands

Eleven archaeomagnetic samples were collected from several sites near Porco, Bolivia as part of the Proyecto Arqueológico Porco-Potosí. These samples were collected in order to 1) explore the availability of appropriate sample materials in the Bolivian Andes, and 2) assess the feasibility of pursuing reference curve research for this region. In addition, this research explored the archaeomagnetic dating application of reference curves constructed from the global geomagnetic field model gufm1 (Jackson et al., 2000), which covers the period from AD 1590–1990. This model is particularly applicable to our project, since many of the project sites are late prehispanic (pre-AD 1532) and early historic (ca. AD 1532–1825) in age. Of the 11 samples, three appeared to contain an insufficient amount of ferromagnetic minerals to provide reliable results, while eight samples produced acceptable-to-good results. The data from the eight good samples were compared to a reference curve for the period of AD 1600–2000 that was calculated for this project from the global field model, gufm1. The archaeomagnetic dates obtained for two of the samples agreed with archaeological expectations, while those for four other samples marginally or greatly postdated the archaeological age expectations. Two additional samples produced significantly different directions and could not be dated against the reference curve. It is likely that the age discrepancies for four of the samples stem from inaccuracies in the archaeomagnetic data, the archaeological age expectations, the calculated reference curve, or some combination of these factors.     

Archaeomagnetic data from four Roman sites in Tunisia

Archaeomagnetic analyses on bricks and slag fragments from kilns have been undertaken. The initial aim of the paper was to constraint the age of four Roman sites in Tunisia (Neapolis, Pheradi Majus, Leptiminus and Sullecthum) using either archaeodirections or archaeointensities. However, the archaeomagnetic models appeared to be only proficient using directions. It has been established that the Neapolis' studied kiln was probably active until the early 6th century AD, whereas the kilns investigated in Pheradi Majus were probably active until the middle 5th century AD. Measured archaeointensities point to higher values than those predicted by the models during the whole range of possible ages for the studied sites.     

Combining an archaeomagnetic and radiocarbon study: dating of medieval fireplaces at the Mühlegasse,Zürich

During the restoration of the Radium cinema located in the old Town of Zürich, a stratigraphic sequence of medieval fireplaces came to light. Based on ceramic finds, a preliminary age of about 1000 AD was assigned. In this paper we show the results from archaeomagnetic and radiocarbon dating, which combined with the stratigraphic information yield a better constrain of the period of use of these fireplaces. Whilst the radiocarbon technique continues to be the most widespread methodology for dating young archeological artifacts, archaeomagnetic dating is becoming increasingly more established in Europe thanks to the increased number of available measurements. A Bayesian model on the period of use of these fireplaces was produced with OxCal, by a combination of magnetic and radiocarbon ages, together with the stratigraphic information. The results show that the fireplaces were probably used during 1 to 2 generations (e.g. 20–40 years each), and are in good agreement with the archaeological context of this site. To make use of the magnetic measurements for future reconstructions of the field, we carried out an additional age model using only the radiocarbon and the stratigraphic information. Although some of the structures show large directional scatter due to poor baking in antiquity, the results confirm the trend of the geomagnetic field around 1000 AD.     

A new approach for geomagnetic archaeointensity research: insights on ancient metallurgy in the Southern Levant

We present results from an archaeointensity investigation based on a relatively unexploited recording medium, copper slag deposits. Together with a recently improved experimental design for the archaeointensity experiment, we demonstrate the applicability of this medium, as well as other archaeometallurgical artifacts, for the study of the ancient geomagnetic field intensity. In addition to archaeointensity data from well-dated archaeological contexts, we obtained reliable archaeointensity results from poorly dated or contentious archaeometallurgical sites in the Southern Levant. These results shed new light on the dating of these sites, among them the copper smelting installation of Timna 39b – a site that has important implications for the beginning of metallurgy during the fifth millennium BCE. The paper also aims to introduce archaeointensity research to the archaeologist scholar, and to encourage further collaboration between the disciplines in future research.     

Lichenometric dating and the nature of the excavation of the Huashan Grottoes,East China

The present study aims to identify the timing of the Huashan Grottoes' excavations using the lichenometric dating method. A total of 96 maximum inscribed circle diameters of Rhizocarpon geographicum growing on the ancient architectures and the walls of entrances are measured in the Huashan Grottoes area of southern Anhui, East China. The results show that the period of the grottoes' excavation is estimated to be 450–335 yr BP, or the middle and late Ming Dynasty (1552–1667 AD). The lichenometric dating results are also validated by a lithologic comparison of the grottoes and the surrounding ancient architectures, as well as by the studies on the historical documents and the fragments of ancient porcelain in the grottoes. Furthermore, we infer that the excavation of the inner grottoes might have lasted till the Qing Dynasty (1636–1912 AD), because the lichens chosen for dating are mainly at the grottoes' entrances. The wider significance of this work is that it demonstrates, for the first time, lichenometric dating can be applied in the historical studies on the ancient architectures in East China with a relatively warm and humid climate.     

Radiocarbon dating of prehistoric hearths in alpine northern Sweden: problems and possibilities

The chronology of prehistoric Sami settlement sites has previously been established by conventional radiocarbon dating of bulk charcoal samples associated with hearths from sunken hut floors (stállo-foundations). Here we present results of a comprehensive dating exercise of stállo-foundations in the alpine area of northern Scandinavia using Accelerator Mass Spectrometry (AMS) radiocarbon dating of charcoal. Over a 3 km² study area, AMS calibrated ages of hearth charcoal from 22 stállo-foundations across 12 sites securely date these features to between cal. AD 640 and AD 1180. Only small variations in age were found between charcoal samples from different areas of a given hearth. Statistical analysis of all the charcoal AMS radiocarbon dates obtained reveals that 12 stállo-foundations across nine sites are contemporaneous and date to the Viking Period (AD 800–AD 1050). The tightly constrained AMS-based chronology of stállo-foundations contrasts with the existing chronology based on conventional radiocarbon analysis, which places these features within a significantly greater time-frame of between AD 600 and AD 1900, with most dates ranging between AD 800 and AD 1350.This discrepancy is likely to result from the necessity of collecting composite hearth charcoal particles, which may originate from different phases of occupation, in order to achieve the required final carbon content for conventional radiocarbon analysis. We argue that the new AMS-based radiocarbon chronology of stállo-foundations presented here supersedes the existing chronology based on conventional (Gas Proportional counting) radiocarbon analysis and we advocate the use of AMS radiocarbon dating in future hearth investigations.     

Palaeoenvironmental significance of grain-size distribution of river flood deposits: a study of the archaeological sites of the Apengjiang River Drainage,upper Yangtze region,Chongqing, China

The grain-size distribution (based on cumulative probability curves) in the sediments produced by potential palaeofloods at the Shiniusi archaeological site is similar to that of modern flood sediments from the Wujiang River Drainage in the upper Yangtze River. There is an obvious pattern in the curves, with two segments, and the mean grain size (Mz), standard deviations (σ1), skewness, and kurtosis are all similar. Combined with the AMS¹⁴C dating data and the ages judged based on the presence of cultural remains, our data suggests frequent palaeoflood events within the Wujiang River Drainage. We hypothesize the existence of seven high flood possibility layers in the QST4 unit from Shiniusi archaeological site: during the periods of the Ming Dynasty (1368–1644 AD) to the Qing Dynasty (1616–1911 AD), and the end of the Eastern Zhou Dynasty (770 BC–256 BC) to the Shang Dynasty (1600–1100 BC). We also hypothesize ten high flood probability layers in the QST2 unit from Shiniusi archaeological site: during the periods of the Ming Dynasty to the Qing Dynasty, the periods of Song Dynasty (960–1279 AD) to the Yuan Dynasty (1206–1368 AD), as well as during the Han Dynasty (207 BC–220 AD) to the Eastern Zhou Dynasty (770 BC–256 BC). These results are consistent with palaeoflood events inferred from pollen and spore analysis and from historical records in other rivers.     

TOWARDS A NEW APPROACH TO ARCHAEOMAGNETIC DATING IN EUROPE USING GEOMAGNETIC FIELD MODELLING*

We introduce a new approach to producing secular variation curves for archaeomagnetic dating, using global geomagnetic field modelling techniques. Using published palaeosecular variation curves for five European locations as input, and a previous global model for regularization, we produce a model for the period ad 0–1900, which reproduces the input curves within their 95% confidence intervals, and successfully fits data from other regions in Europe. Our global model performs as well as a previous regional model, but additionally ensures consistency with physical constraints. We show that the curves currently used for dating are not mutually consistent, and therefore that in the future this new approach will provide more reliable curves for archaeomagnetic dating.