Archaeomagnetism Research Papers - Academia.edu (original) (raw)

Three kilns and a collection of baked bricks from Italian archaeological sites have been studied for archaeointensity determination using the Thellier method as modified by Coe. All sites are dated based on archaeological information and their ages range from 500 to 800 AD and 1500 to 1700 AD. Rock magnetic studies identify magnetite, Ti- magnetite and hematite as the main magnetic minerals, and magnetic susceptibility versus temperature shows a good thermal stability of the samples. The intensity results have been corrected for anisotropy of the thermoremanent magnetization and cooling rate effects. The new data together with 136 previously published results are used to estimate the variation of the Earth's magnetic field over the past three millennia. The time distribution of the Italian absolute intensity data is irregular with the majority of determinations concentrated during the last four centuries, while older periods are very poorly covered. Most of the data come from vo...

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- Geology, Geophysics, Rock magnetism, Archaeomagnetism

Here we report a detailed archaeomagnetic and rock-magnetic study of a pottery kiln from Burgos (Spain) to reconstruct its burning conditions and date its last use and abandonment age. During the course of a rescue archaeological excavation carried out in 2015 in the center of Burgos city, a medieval pottery workshop was discovered. Two well-preserved kilns appeared and archaeomagnetic analyses were performed on one of them. In addition to a large amount of pottery remains, some numismatic and documental evidences provided a general chronological estimation, but the abandonment age of the workshop remains unknown. On the basis of the existing archaeological information we carried out an archaeomagnetic study in order to date its last use. 69 archaeomagnetic samples were collected from the combustion chamber and the kiln's fire tunnel. Stepwise alternating field and thermal demagnetization of the natural remanent magnetization (NRM) were carried out to retrieve the mean direction. Additional experiments consisted in the acquisition of isothermal remanence (IRM), low-field magnetic susceptibility and its anisotropy as well as thermomagnetic curves. Despite the high temperatures expected in the combustion chamber, it appeared that the bricks´ samples from the fire tunnel exhibit the most successful directional results. Magnetite and variable contributions of hematite are the main ferromagnetic minerals observed in the thermomagnetic curves. The type of lithology studied, its previous magnetic history and their location in the kiln strongly condition the observed directional and rock-magnetic results. Additionally, AMS data revealed the manufacturing fabric of the fire tunnel's bricks, showing moderately high anisotropy degrees, but not enough to casts doubts on the directional NRM record. In order to test the reproducibility of the dating results, archaeomagnetic dating was carried out using different geomagnetic field models and the Iberian secular variation curve. The small differences observed in the dating results are mainly due to the density and type of input data of these records. The combination of the archaeomagnetic analyses with the archaeological and documental suggests that last kiln's usage took place during the first half of the XVIth century CE. Overall, this paper illustrates how the combination of archaeological data and archaeomagnetic analyses may improve our understanding about the manufacturing processes, use and age of abandonment of archaeological combustion structures.

- by Carmen Alonso Fernández and +3
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- Rock magnetism, Archaeomagnetism, Archaeomagnetic Dating, Geocronología

This volume contains the following articles: "Editor's Preface" by Daniel H. Sandweiss; "Heidy Fogel, 1956-1994" by Richard L. Burger; "Daniel Wolfman, 1939-1994" by Izumi Shimada; "The Inca Compound at La Centinela, Chincha" by Dwight Wallace; "Reconstructing the Great Hall at Inkallacta" by Vincent R. Lee; "Reconstructing Andean Shrine Systems: A Test Case from the Xaquixaguana (Anta) Region of Cusco, Peru" by Brian S. Bauer and Wilton Barrioneuvo Orosco; "The Temple of Blindness: An Investigation of the Inca Shrine of Ancocagua" by Johan Reinhard; "Ethnogenesis in Huamachuco" by John R. Topic; "Coca Production on the Inca Frontier: The Yungas of Chuquioma" by Catherine J. Julien; Creating a Ruin in Colonial Cusco: Sacsahuaman and What Was Made of It" by Carolyn S. Dean; "The Alca Obsidian Source: The Origin of Raw Material for Cusco Type Obsidian Artifacts" by Richard L. Burger, Frank Asaro, Paul Trawick, and Fred Stross; "The Chivay Obsidian Source and the Geological Origin of Titicaca Basin Type Obsidian Artifacts by Richard L. Burger, Frank Asaro, Guido Salas, and Fred Stross; "The Jampatilla Obsidian Source: Identifying the Geological Source of Pampas Type Obsidian Artifacts from Southern Peru" by Richard L. Burger, Katharina J. Schrieber, Michael D. Glascock, and Jose Ccencho; "Unifaces in Early Andean Culture History: The Nanchoc Lithic Tradition of Northern Peru" by Jack Rossen; "Lithic Provenience Analysis and Emerging Material Complexity at Formative Period Chiripa, Bolivia" by David L. Browman; "Textiles from the Lower Osmore Valley, Southern Peru: A Cultural Interpretation" by Ran Boytner; "Corbel Vaulted Sod Structures in the Context of Lake Titicaca Basin Settlement Patterns" by Sergio J. Chavez; "Archaeomagnetic Results from Peru: A.D. 700-1500 by Daniel Wolfman and Richard E. Dodson.

- by Monica Barnes and +3
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- Architecture, Andean Archaeology, Textiles, Obsidian
- by Karen Radner
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- Iron Age (Archaeology), Archaeomagnetism, Iron Age, archaeology in Iraq

Copper Archaeometallurgy Archaeomagnetism Bronze Age Faynan Negev Old Kingdom a b s t r a c t This paper presents results of an archaeomagnetic study of slag from four Early Bronze (EB) Age copper production sites in the Faynan Copper Ore District and the northern Arabah Valley (modern Israel and Jordan). The results provide age constraints for metallurgical activities at these sites. Together with previously published data, they indicate copper production around ca. 2900 cal. BCE (EB II-III transition) and between ca. 2600-1950 cal. BCE, spanning the later part of the EB III and the entire EB IV period. These data strongly suggest a direct link between Faynan and the Old Kingdom of Egypt, which is reflected in the most significant phase of copper production and trade in the northern Arabah prior to the Iron Age, and in a settlement wave in the Negev Highlands. In addition, the results indicate that during the late EB II copper was smelted up to 40 km away from the mines. This is evident at the unique cultic site of Ashalim, located on the main road between Faynan, southeast of the Dead Sea, and the settled areas in the core of Canaan.

- by Erez Ben-Yosef and +3
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- Paleomagnetism, Archaeometallurgy, Old Kingdom (Egyptology), Early Bronze Age (Archaeology)

Teotihuacan is considered as the best planned and largest pre-Hispanic city in Mesoamerica. One of the causes, related to the decline of the Teotihuacan, is the so-called "Big Fire". However, associated chronological constraints are still poorly defined. Here, we report new archaeomagnetic dates of three burned walls located in the Plaza de la Luna vicinity, considered as the last construction stage of Teotihuacan. Detailed rock-magnetic and absolute archaeointensity studies were performed on 24 samples allowing to determine both mean directions and absolute intensities. Magnetic dating using full geomagnetic vector provided a time interval between 327 and 441 CE as the best estimate of the last fire exposure of studied footprints. This new data, in combination with previous results, suggest that Teotihuacán experienced various fire episodes probably caused and controlled during public acts loaded with symbolic values, such as the rituals for the termination of a cycle or those related to the beginning of a new constructive stage.

- by Veronica Ortega Cabrera and +1
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- Archaeology, Teotihuacan, Mesoamerica, Archaeomagnetism
- by Przemysław Makarowicz and +5
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- Archaeomagnetism, Ukraine, Magnetometry, Non-invasive archaeological survey

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.

An integrated magnetic survey was carried out on key places within the La Quemada archaeological complex, built over a hill on the northern frontier of Classic period Mesoamerica. Samples were collected from the Plaza of Sacrifices and Hall of Columns in an attempt to precisely determine the age intervals corresponding to the decline and abandonment of the site, apparently due to the intentional firing as a closure ritual. Well-defined char- acteristic remanent magnetizations were retrieved from 23 of 32 samples. Moreover, twelve samples belonging to two areas yielded reliable determinations under criteria curtailed in this study. In any case, a primary re- manent magnetization is carried by pseudo-single-domain Ti-poor titanomagnetite, as evidenced by hysteresis and continuous thermomagnetic curves. The archaeomagnetic dating was performed using full geomagnetic vector (directions and absolute intensity) using the last SHADIF14k model. The Plaza of Sacrifices seems to been burned between a time interval from 854 to 968 CE, while a late interval from 1018 to 1163 CE is assigned to the samples collected in the Hall of Columns, which suggest the gradual abandonment of the site. The first aban- donment stage is almost synchronous to the same phenomena observed for other sites at the Bajío area (central and western Mesoamerica) region. Under these circumstances, it cannot be discarded that La Quemada was burned in its entirety during the first stage of abandonment, but the Hall of Columns was again burned later.

- by Peter Jimenez and +3
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- Mesoamerican Archaeology, Mesoamerica, Frontier Studies, Archaeomagnetism

The archaeological site of El Mirador is located in the southern slope of the Sierra de Atapuerca. The work developed at the site is providing a substantial set of data from the Upper Palaeolithic and Early Neolithic to the Middle Bronze Age. Throughout at least about 4000 years of occupation, the cave was used for various activities, among which, burial, habitation and animal stalling. The practices related with this last use is, at the moment, the main origin of the archaeological deposits, which are mainly composed by burnt animal dung with vegetal residues, potsherds, lithics and faunal remains. In addition, it is characterized by high sedimentation rates that have enabled an individual and clear record of different episodes, providing high resolution chronological data. Due to these particularities, specific excavation methodology and interdisciplinary studies of the archaeological data have been developed in order to understand the genesis of this archaeological sequence and, at the same time, to provide information about the introduction and development of the production economy in the Submeseta Norte region.

- by Josep Maria Vergès and +3
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- Experimental Archaeology, Prehistoric Archaeology, Palaeolithic Archaeology, Rock magnetism

This study applied for the first time archaeomagnetic experiments to Ancient Near Eastern burned clay tablets. The tablets used in the experiments originated from Hattusa, the capital of the Hittite kingdom in the Late Bronze (1650-1178 BCE) and a Cypro-Minoan tablet from Enkomi in Cyprus. The goals were: (1) Checking the quality of tablets as an archaeomagnetic recorder. (2) Enhancing the reference curve with chronologically-anchored geomagnetic intensity values based on well-dated tablets. (3) Studying the firing history of the tablets. (4) Assessing the potential of archaeomagentism to assist with studies related to reconstruction of original contexts and reconstruction of tablets from fragments. As archaeointensity recorders, clay tablets can have tighter age constraints than most of the commonly used materials (e.g., pottery, slags) due to their historical content. The results show that (1) Baked clay tablets are a viable source of archaeointensity recorders. (2) Emphasis should be given to connecting the historical date with the firing event; when the two are found to be linked, clay tablets can provide ‘anchors’ of geomagnetic intensity values in time resolution of less than 30 years. (3) The archaeomagnetic method can be used to establish the original location of clay tablets of unknown origin. The results show two tablets with the same archaeointensity, when one of the tablets came from The "House on the Slope" in Hattusa (VAT 13012), and the other was of unknown origin (VAT 7487). The probability of the two coming from the same place is high, as the burning of the two happened in the same place and time, in accordance with the archaeointensity results and the assumption that their firing was the result of fires. (4) Dating tablet of an unsecured origin.

- by Yitzhak Vassal
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- Archaeology, Hittitology, Archaeomagnetism, Cuneiform
- by Sarah-Jane Clelland
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- Archaeology, Archaeomagnetism, Iron Age

- by Veronica Ortega Cabrera
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- Archaeology, Architecture, Mesoamerican Archaeology, Teotihuacan

Background: GEOMAGIA50.v3 is a comprehensive online database providing access to published paleomagnetic, rock magnetic, and chronological data from a variety of materials that record Earth's magnetic field over the past 50 ka. Findings: Since its original release in 2006, the structure and function of the database have been updated and a significant number of data have been added. Notable modifications are the following: (1) the inclusion of additional intensity, directional and metadata from archeological and volcanic materials and an improved documentation of radiocarbon dates; (2) a new data model to accommodate paleomagnetic, rock magnetic, and chronological data from lake and marine sediments; (3) a refinement of the geographic constraints in the archeomagnetic/volcanic query allowing selection of particular locations; (4) more flexible methodological and statistical constraints in the archeomagnetic/volcanic query; (5) the calculation of predictions of the Holocene geomagnetic field from a series of time varying global field models; (6) searchable reference lists; and (7) an updated web interface. This paper describes general modifications to the database and specific aspects of the archeomagnetic and volcanic database. The reader is referred to a companion publication for a description of the sediment database. Conclusions: The archeomagnetic and volcanic part of GEOMAGIA50.v3 currently contains 14,645 data (declination, inclination, and paleointensity) from 461 studies published between 1959 and 2014. We review the paleomagnetic methods used to obtain these data and discuss applications of the data within the database. The database continues to expand as legacy data are added and new studies published. The web-based interface can be found at http:// geomagia.gfz-potsdam.de.

- by Stacey Lengyel
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- Paleomagnetism, Geomagnetism, Archaeomagnetism
- by Erez Ben-Yosef
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- Biblical Archaeology, Archaeomagnetism, Iron Age
- by Georgios Polymeris and +1
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- Archaeology, Cultural Heritage, Archaeomagnetism, Dating

Apart from magnetostratigraphy, archaeomagnetism is rarely used in Middle and Late Pleistocene sites. Here we present detailed palaeomagnetic analyses of cemented hearths and burnt chert items from Amud Cave, Israel (68-55 ka)-two types of materials common in Levantine Middle Palaeolithic cave sites. Both materials are shown to be recorders of the geomagnetic field and were used to reconstruct either the ancient field direction (for cemented hearths) or intensity (palaeointensity) (for chert) at the time of the last burning or shortly after. We test the utility of palaeomagnetic data to further our understanding of temporal aspects of occupations in the cave by comparing the dispersion of the palaeomagnetic data to the known characteristics of geomagnetic secular variation in the Holocene. We show that divergent palaeointensities can help identify diachronic burning events, suggesting different activity patterns in two areas of the cave. Additionally, we used palaeomagnetic directional vectors to distinguish between a well-preserved hearth and one that had been mixed prior to cementation. Using rock magnetic investigations, we demonstrate that magnetic methods can be used as a relatively fast and inexpensive method to identify burning of cherts in antiquity above 500 °C. The palaeomagnetic results are in agreement with results of previous studies at Amud Cave, obtained by other independent methods. This study shows that palaeomagnetic methods can serve as a powerful tool in the study of Palaeolithic sites.

- by Erella Hovers and +1
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- Prehistoric Archaeology, Neanderthals (Palaeolithic Archaeology), Archaeomagnetism, Archaeological Site Formation Processes

Rapport sur les campagnes 2012-2013 aux abords Nord de l'Artémision de Thasos. Résultats sur la demeure protobyzantine DOM5 (en particulier : phasage du chantier d'agrandissement du triklinos ; destruction par un seîsme en 620 ; environnement de la demeure) et sur les édifices qui l'ont précédé (BAT25, d'époque archaïque, et BAT24, en usage du IVe s. av. J.-C. jusqu'à son intégration dans l'aile Nord de la demeure protobyzantine DOM5).

- by Arthur MULLER and +8
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- Archaeology, Late Antique and Byzantine Studies, Byzantine Archaeology, Housing and Dwelling (Architecture)

Recent excavations at Corent (France) unearthed a vast Late Bronze Age settlement. The high density of fireplaces especially highlights it. The present study focuses on the archaeomagnetic study of five fireplaces. These ones were dated between 950 and 800 BCE by cross-dating of metallic and ceramic artefacts and by radiocarbon. The main objective of our study is to increase the archaeointensity database in Western Europe at the beginning of the first millennium BCE. The sampling was conducted on 64 fragments of baked clay and sherds from the fireplaces floor. The classical Thellier-Thellier protocol provides 48 successful archaeointensity results, yielding to five mean values between 58 and 69 μT at the site. Together with previously published results, our new data point out two successive maxima of the intensity of the geomagnetic field. The first maximum ~70 μT in the ninth century BCE and the second ~90 μT in ~ 700 BCE are separated by a ~45–50 μT minimum at ~800–750 BCE. The resulting fast variation of the field intensity will be very useful for archaeomagnetic dating purposes. As the direction of the geomagnetic field has also a strong variation during this period (Hervé et al. 2013a), archaeomagnetism promises to be a powerful dating tool to recover the historical processes at the transition between the Bronze and Iron Ages in Western Europe.

- by Gwenael Herve
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- Late Bronze Age archaeology, Archaeomagnetism, Archaeointensity

La investigación que presentamos es sobre el hallazgo y la datación arqueomagnética de hornos de cal en el área maya, México. La relevancia de la datación arqueomagnética consiste en localizar las construcciones arquitectónicas y dilucidar el periodo de utilización por las sociedades que habitaron la zona de ubicación de dichas construcciones. Asumimos que se trataba de hornos prehispánicos por su asociación con el contexto de la excavación. Sin embargo, los resultados de la combinación de dataciones y métodos arqueométricos permitieron ubicar estas estructuras en distintos periodos de utilización y, por tanto, asumir la continuidad de esta tecnología productiva más allá del periodo prehispánico. Asimismo los trabajos de datación nos permiten clarificar la utilización de esta tecnología y práctica productiva en dicha zona cultural.

- by Soledad Ortiz Ruiz and +1
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- Archaeometry, Maya Archaeology, Archaeomagnetism, Archaeomagnetic Dating

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.

- by Rob Sternberg
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- Archaeology, Geochemistry, Archaeometry, Archaeomagnetism

El presente trabajo analiza un conjunto
de fragmentos cerámicos correspondientes a tinajas
de gran tamaño recuperadas en el sector de
Talleres del sitio arqueológico Guachimontones,
Jalisco, México (fig. 1). La cerámica en estudio guardaba
relación con unidades habitacionales, sin embargo se desconocía su funcionalidad en este espacio.
Por tal motivo se aplicaron técnicas arqueométricas
y arqueomagnéticas para conocer su
uso específico, su funcionamiento dentro de la organización
social y su cronología. El punto de partida
del análisis es la idea de que estas tinajas
sirvieron para la preparación de tejuino (bebida fermentada
elaborada a partir de maíz); esto se debe,
en gran medida, a las comparaciones etnográficas
con otras regiones. Los resultados obtenidos de la
datación arqueomagnética nos permitieron comprobar
que las tejuineras son parte del periodo Posclá-
sico del sitio, y que las edades obtenidas son muy
similares a las ya publicadas para el Posclásico del
sitio arqueológico de Guachimontones.

- by Miguel Angel Novillo Verdugo and +1
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- Mesoamerican Archaeology, Archaeomagnetism, West Mexico (Archaeology), Alcohol Drinking

The present article comprises a multidisciplinary archaeometric approach for the study of Hellenistic and Early Roman kilns in Greece. A collection of previously published and new archaeomagnetic data are combined with new results from mineralogical analytical experiments. The sampled material came from four areas, covering different geological contexts: Katerini, Olympiada, and Polymylos in mainland Greece, and the island of Paros. Extensive rock-magnetic experiments, including identification of the dominant ferromagnetic minerals present, their domain state, and mineralogical alterations during laboratory treatments, have been carried out in order to examine the magnetic properties of the studied materials and prove their suitability for reliable archaeomagnetic determinations. Magnetic cleaning provided well-defined archaeomagnetic directions, and archaeointensity measurements were carried out using both the Thellier-Thellier and Triaxe protocols. Information from both magnetic and mineralogical properties referring to firing conditions is further discussed along with archaeological information. Finally, a new dating of the four sites together with other structures of similar age was carried out using the Pavón-Carrasco model.

- by Irene Zananiri
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- Archaeology, Geochemistry, Radiocarbon, Archaeomagnetism

Uncertainty in radiocarbon dates for the Near East, caused by a bimodal distribution of ages due to the natural fluctuations of 14C in the atmosphere, has demonstrated the need for an alternative absolute dating technique to aid in the construction of site chronologies. Here we present a new archaeointensity reference curve model for the first three millennia BCE for the Levant (Syria, Israel, Jordan) for use in archaeomagnetic dating and contribute twelve new intensity results to an increasingly dense geomagnetic field record for the period between 2400 and 1200 BCE in the Near East. Archaeomagnetic analysis was conducted on ceramic samples (i.e. pottery sherds) from seven sequential and well-constrained occupational layers at the site of Tell Mozan (Bronze Age Urkesh) in northeastern Syria, resulting in a 90% success rate by specimen (n=42) for archaeointensity determination and an 86% correspondence between the model and the archaeologically derived dates within one standard deviation (1σ). Age standard deviations as low as ±24 years were obtained after integration with stratigraphic constraints. We also outline the techniques and sampling procedures of archaeomagnetic dating in a manner suitable for the non-paleomagnetist while detailing methodology for archaeomagnetic researchers.

- by Michele Stillinger and +2
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- Near Eastern Archaeology, Archaeological Science, Bronze Age Archaeology, Archaeological Geophysics

For the first time results of an archaeomagnetic study of unburned lime-plasters from Teotihuacan and Tenochtitlan in central Mesoamerica are presented. Plasters made of lime, lithic clasts and water, appear during the Formative Period... more

- by Linda R . Manzanilla-Naim
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- Geology, Geochemistry, Geophysics, Archaeomagnetism

T he Earth's magnetic field is dynamic, with fluctuations that range from minute daily variances to massive polar field reversals that occur with a frequency on the order of one million years. Magnetic minerals in heat-treated archaeological materials have the ability to store a record of these past field changes, which can be measured using modern superconducting rock magnetometers. For example, artifacts such as fired pottery or slag from metal production contain magnetic minerals that record the Earth's field strength and direction as they are cooled from high temperatures (such as those typical in ceramic kilns), providing a fixed record of the ancient field at the time of their manufacture. Compilations of well-dated sequential field measurements can act as reference curves, which can be used to estimate the age of other heat-treated archaeological materials. This is the basis for archaeomagnetic dating, an important chronological method that, as demonstrated below, is powerful even at sites that yield suitable materials for radiocarbon analysis.

- by Erez Ben-Yosef and +2
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- Paleomagnetism, Archaeometry, Biblical Archaeology, Iron Age (Archaeology)

I n the June 2016 issue of Near Eastern Archaeology,
Michele D. Stillinger, James W. Hardin, Joshua M. Feinberg,
and Jeffrey A. Blakely published a paper entitled
“Archaeomagnetism as a Complementary Dating Technique
to Address the Iron Age Chronology Debate in the Levant”
(Stillinger et al. 2016). The article addresses a key issue in the
Iron Age chronology debate, namely, long date ranges of calibrated
radiocarbon determinations caused by the considerably
flat shape of the calibration curve in the tenth century b.c.e.
(fig. 1). As a result, radiocarbon dating frequently does not
provide the precision desired by archaeologists for answering
chronological questions, such as the Iron Age I–IIA transition.
Distinguishing between an early or late tenth-century b.c.e.
date based on single calibrated radiocarbon determinations is
close to impossible without the aid of Bayesian analysis (fig. 2).

- by Katharina Streit and +1
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- Archaeology, Near Eastern Archaeology, Biblical Archaeology, Ancient Near East

O campo magnético da Terra oscila em várias escalas de tempo
tanto em direção quanto em intensidade. As oscilações na escala de tempo arqueológico (1,7X 103 a 1X104 anos) são de origem interna (no núcleo externo, líquido e condutor), têm abrangência regional (~200.000 km2) e correspondem à parte das variações seculares do campo geomagnético. O estudo dessas variações em diferentes partes do globo permite construir curvas de referência. Quando bem conhecidas, essas curvas podem ser
utilizadas na datação arqueomagnética, que consiste na comparação de um dado arqueomagnético obtido em um artefato ou estrutura arqueológica com a curva de referência para a região em estudo. Neste trabalho são apresentados os princípios do arqueomagnetismo, as formas como o campo é registrado em
material arqueológico, as técnicas para obtenção de dados arqueomagnéticos e os métodos utilizados na datação arqueomagnética. Além disso, são apresentadas as perspectivas para o arqueomagnetismo no Brasil e a aplicação desta técnica
de datação na porção meridional da América do Sul.

- by Marisa Afonso and +1
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- Ceramics (Archaeology), Archaeomagnetism, Archaeomagnetic Dating

Keywords: archeomagnetism archeointensity geomagnetic secular variation historical geomagnetic field Northeast Brazil southern hemisphere This study presents the first archeointensity results from Northeast Brazil obtained from 14 groups of architectural brick fragments sampled in the city of Salvador, Bahia State (13°S, 38.5°W) and dated between the middle of the XVIth century and the beginning of the XIXth century. The dating is ascertained by historical documents complemented by archeological constraints, yielding in all cases age uncertainties of less than 50 years. Analyses were carried out using two experimental protocols: 1the "zero field-in field" version of the classical Thellier and Thellier method as proposed by Coe (TT-ZI), including partial thermoremanent magnetization (pTRM) and pTRM-tail checks, and 2the Triaxe procedure involving continuous high temperature magnetization measurements. Both TRM anisotropy and cooling rate effects were taken into account for the intensity determinations. The cooling rate effect was further explored for the TT-ZI protocol using three increasing slow cooling times (5 h, 10 h and 25 h) between 450°C and room temperature. Following archeological constraints, the slowest cooling time was retained in our study, yielding decreases of the raw intensity values by 4% to 14%. For each fragment, a mean intensity was computed and retained only when the data obtained from all specimens (between 2 and 6) satisfied a coherence test at ∼ 5%. A total of 57 fragments (183 specimens) was considered for the computations of site-mean intensity values, with derived standard deviations of less than 8% of the corresponding means. When separately computed using the two experimental techniques, the site-mean intensity values always agree to within 5%. A good consistency is observed between intensity values of similar or close ages, which strengthen their reliability. Our data principally show a significant and continuous decrease in geomagnetic field intensity in Northeast Brazil between the first half of the XVIIth century and the XXth century. One result dated to the second half of the XVIth century further suggests that the geomagnetic field intensity reached a maximum around 1600 AD. This evolution is in good agreement with that expected in the city of Salvador from the available global geomagnetic field models. However, the accuracy of these models appears less well constrained between ∼ 1550 AD and ∼ 1650 AD.

Excavations on the first- and second-century Roman military earthwork complex known as Cawthorn Camps, located north-west of Pickering, North Yorkshire confirmed the broad dating of the major features through artefacts and archaeomagnetic dating. Earthworks A and D were shown to be forts of two phases. Within Fort A and Annexe B well-preserved turf structures were examined which were shown to be buildings associated with the Roman military occupation. The interior of Fort D was shown to be heavily disturbed by later activity, although the defences survived remarkably well. The well-defined turf structure of the second phase rampart was revealed and the existence of four phases of inner ditch was demonstrated. In addition to the Roman military remains two major features sealed by the pre-Roman buried soil provided evidence of prehistoric occupation. The re-examination of one of the ‘Officer’s dug-outs’ investigated by Sir Ian Richmond in the 1920s showed it to be an early medieval Grubenhaus, unfortunately no datable material remained in situ. Overall the artefact and ecofact assemblages were sparse. This report represents a summary of the data available at the completion of the site archive and presents preliminary interpretations of the data.

Meaningful interpretation of past human culture and political geography requires an accurate chronology that can be correlated with our modern calendar. The timing of seminal events during the Levant Iron Age is hotly debated because conventional dating methods are limited by subjective interpretations and analytical ambiguities. Archaeomagnetism, the study of the Earth’s ancient geomagnetic field recorded by heat-treated anthropogenic objects, can provide a complementary dating tool to build a stronger, more robust chronology for the Iron Age. Here we present a description of the field of archaeomagnetic dating, and a brief overview of the chronological issues and radiocarbon dating problems for the Iron Age Levant. We also present a new Near East Archaeomagnetic Curve (NEAC) model for the region along with preliminary data from Khirbet Summeily, Israel.

- by Michele Stillinger and +1
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- Levantine Archaeology, Iron Age (Archaeology), Archaeomagnetism, Archaeology of the Southern Levant

We present new, full geomagnetic field vector results from three Neolithic ovens discovered at the archaeological site of Portonovo (Marche, Italy). The discovered structures are a rare example of very well preserved underground ovens from the Early Neolithic period. Standard thermal demagnetization procedures were used to isolate the direction of the Characteristic Remanent Magnetization acquired by the baked clay during the ovens' last firing. The corresponding archaeointensities were determined by the multi-specimen procedure (MSP-DSC) and show a clear intensity low during the Neolithic period. Both directional and intensity results are of high quality, offering the first contribution of full geomagnetic field vector data for this period in Italy. The new data are compared with other contemporaneous data from Europe and with global geomagnetic field models. Independent archaeomagnetic dating of the three ovens was also performed by means of the SCHA.DIF.14k model. The obtained results are in excellent agreement with available radiocarbon dates and confirm that all ovens belong to the Neolithic. These new data importantly enrich our knowledge of the geomagnetic field during the Neolithic period that is poorly documented by data, not only in Italy but also in the whole of Europe and show that archaeomagnetic dating can provide precise results even for prehistoric periods.

- by Cecilia Conati Barbaro and +2
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- Prehistoric Archaeology, Geomagnetism, Neolithic Archaeology, Neolithic Europe

Recent archaeomagnetic studies carried out on Mid-to Late Holocene burnt anthropogenic cave sediments
have shown that under certain conditions, these materials are suitable geomagnetic field recorders.
Archaeomagnetic analyses carried out on these contexts constitute a rich source of information
not only for geophysical purposes -in terms of reconstructing the variation of Earth's magnetic field in
the past- but also from the archaeological point of view, for example by archaeomagnetic dating. Here,
we report three different archaeomagnetic applications to the study of burnt cave sediments: (i)
archaeomagnetic dating; (ii) determining palaeotemperatures and (iii) assessing post-depositional
processes. The first case study is a dating attempt carried out on a Late Holocene (Bronze Age) burnt
level from El Mirador Cave (Burgos, Spain). Using the directional European secular variation curve,
several dating intervals were obtained for the last burning of this combustion feature. Considering the
archaeological evidence and the independent radiometric (14C) dating available the possible ages obtained
are discussed. This is the first archaeomagnetic dating obtained in these contexts so far. The
second case study is an application of the method to determine the last heating temperatures reached by
the carbonaceous facies of these fires. Stepwise thermal demagnetization of oriented samples can be
used to quantitatively estimate heating temperatures. An intermediate normal polarity component
interpreted as a partial thermo-remanence (pTRM) with maximum unblocking temperatures of 400
e450 C was systematically identified, revealing the last heating temperatures experienced by this facies.
These temperatures were confirmed with partial thermomagnetic curve experiments. Finally, archaeomagnetic
analyses on a partially bioturbated burning event were performed in order to evaluate until
what spatial extent the burnt sediments were affected by post-depositional mechanical alteration processes.
For each case study, the archaeological implications are discussed highlighting the potential of
archaeomagnetic methods to retrieve archaeological information.

- by Ángel Carrancho and +2
- •
- Rock magnetism, Geochronology, Archaeomagnetism, Prehistory

We have used rock magnetic techniques in this study to assess atmospheric pollution at five stations in and around Mangalore city on the southwestern coast of India. Samples of dust were collected from two suburban areas (Thokkottu and Pumpwell located respectively~10 km and 3 km from the city center), the city center itself (Milagres) and industrial/port areas (Panambur and Mangalore Refinery and Petrochemicals Limited (MRPL)). Low-frequency magnetic susceptibility (χ lf ), frequency-dependent susceptibility (χ fd ), susceptibility of anhysteretic remanent magnetization (χ ARM ) and isothermal remanent magnetization (IRM 20 to 1000 mT) were determined on 23 dust samples and inter-parametric ratios calculated. Results show that samples from suburban areas (particularly Thokkottu) are characterized by low χ lf (b314.1 × 10 −8 m 3 kg −1 ) and up to 6% χ fd , suggesting low levels of pollution and the presence of pedogenic magnetite possibly derived from soils by wind erosion. However, the average χ lf of Milagres, Panambur and MRPL dust samples is high by factors of 9.2, 3.3 and 2.6 compared to that of the Thokkottu sample. The Milagres sample contains magnetically "soft" minerals like magnetite, possibly indicating its derivation from motor vehicle exhaust. In contrast, the Panambur dust sample is characterized by magnetically "hard" minerals such as hematite and goethite as it has an 8-fold higher HIRM value compared to the Thokkottu sample. This magnetic signature is perhaps the result of dust particles derived from the grinding of hematite-rich iron ore by the Kudremukh Iron Ore Company Limited (KIOCL) at Panambur and its storage and export through the nearby New Mangalore Port. However, the dust sample from MRPL has magnetically "soft" minerals like magnetite. This magnetic mineral may have originated from petroleum refining processes at MRPL. Particulate pollution from industrial activities and motor vehicle exhaust is a threat to human health and is known to cause cardiovascular and respiratory ailments. Therefore, the pollution levels brought out by this study warrant a comprehensive epidemiological study in the area of study.

- by HARSHAVARDHANA B G
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- Palaeoclimatology, Geomagnetism, Archaeomagnetism, Environmental Magnetism

Hillforts have been the focus of British Iron Age studies since the beginnings of field archaeology due to their conspicuous presence in the present day landscape. It has been noted that that there were different methods of constructing the key characteristic of hillforts, namely the presence of a circuit (or part) of artificial enclosing works. This prompted both the process of classifying these groups and attempts to trace the origin of these methods of construction. One of these subgroups is timber-laced ramparts and examples have been found all over Britain. However, in northern Britain over sixty timber-laced ramparts exhibit signs of vitrification; a feature that appears to be unique to this area of Britain but has also been observed on the continent, particularly the Atlantic fringes. Seven British vitrified hillfort sites have been sampled for archaeomagnetic dating and previous research has highlighted huge discrepancies in the dating of what appear to be a morphologically similar class of sites. This paper will present a re-evaluation of the dating evidence provided by earlier workers and will use these seven sites as a case study to introduce an updated version of the British archaeomagnetic calibration curve.

- by Sarah-Jane Clelland
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- Archaeology, Archaeomagnetism, Iron Age, Hillforts and Enclosures

Geomagnetic field variations at archeomagnetic timescales can be obtained from well-dated heated structures and archeological potsherds. Here, we present the first archeointensity results obtained on Portuguese ceramics (1550 to 1750 AD) collected at Brazilian archeological sites. The results are compared to those obtained from Western Europe and currently available geomagnetic field models. Continuous thermomagnetic and IRM acquisitions curves indicate that Ti-poor titanomagnetite is responsible for the remanence in these ceramic fragments. Five fragments (24 samples) out of twelve analyzed yielded reliable intensity estimates. The row archeointensity data were corrected for TRM anisotropy and cooling rate effect. The mean dipole moments are obtained for three different age intervals: 1550±30 AD, 1600±30 AD and 1750±50 AD. Mean intensities vary from 37.9±4.2 μT to 54.8±7.6 μT in agreement with the previously reported data for 1550 AD and 1750 AD. Relatively weaker, but still highly dispersed, values were obtained for 1600 AD ceramics.

- by Marisa Afonso and +1
- •
- Archaeomagnetism, Archaeointensity, Portuguese Potteries

In the mid 1990's a new technique was developed for the presentation of gradiometer surveys of ironworking sites, using filled contour plots with a non-linear scale. This emphasises the dipolar signals which indicate the location of iron smelting furnaces or smithing hearths. This is a potentially powerful technique for mapping sites with the remains of high-temperature features.

Most materials in archaeological sites are capable of acquiring a magnetisation, when heated, that record the direction and intensity of the Earth's magnetic field at that time and place. Within an area of 10 6 km 2 , such archaeomagnetic readings can be compared after minimal correction for the spatial effects of the geomagnetic field. This enables data from all of Egypt to be used to compile a record of the changing geomagnetic field that can be used for relative dating and, when sufficient data are available, absolute dating. Relative dating using directions is potentially capable of dating within some ±25 yr on directions and some ±50 yr in intensity. It is suggested that the validity of the few suspected errors in the Egyptian pharonic calendar can be tested using archaeomagnetic data.

- by Don Tarling
- •
- Archaeology, Egyptian Archaeology, Archaeomagnetism, Archaeomagnetic Dating

We report on the first archaeomagnetic directional data obtained from Syria. Reliable palaeomagnetic directions were collected from four pyrotechnological archaeological structures dated by type of pottery and radiocarbon from the 19th to 8th century BC (Middle Bronze to Iron Age) in Tell Mishrifeh/Qatna, Syria. Fairly constant northward declination values (within confidence limits) were obtained, whereas inclination values increased from 42.3 • to 73.0 • from the Middle Bronze to Iron Age. At first approximation, these new data are consistent with coeval archaeomagnetic directions from Western Europe and Bulgaria. The high inclination (73.0 • ± 2.8 • ) documented for the Iron Age (translating to a VGP latitude of 65.9 • N) suggests that very strong secular variation was occurring during the 8th century BC.

- by daniele morandi bonacossi
- •
- Archaeomagnetism, Syria (Archaeology), Archaeomagnetic Dating, Qatna

- by ethel allue
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- Archaeology, Experimental Archaeology, Prehistoric Archaeology, Geology

Extensive rock-magnetic investigations have been carried out on baked clays from four kilns (two from Bulgaria and two from Switzerland) found in archaeological sites of different age. Knowledge of the magnetic characteristics of the grains responsible for the archaeomagnetic signal enables us to determine which baked clays have the stablest magnetization and why this is so. This is important in directional studies, but even more so in painstaking palaeointensity studies that require a very careful evaluation of the suitability of the burnt clay material. The proposed rock-magnetic experiments enable the identification of the carriers responsible for the remanence and an adequate interpretation of the experimental results connected with the palaeointensity evaluation. The experimental methods employed are illustrated with the particular results obtained from each of the four kilns studied. The preliminary elucidation of the magnetic mineralogy of the archaeological samples helps first by obtaining a more reliable palaeointensity result, and secondly by explaining some of the discrepancies in the palaeodirectional results. Examples of successful and failed palaeointensity experiments are given in relation to the magnetic properties previously established for each oven. The burnt-clay materials in this present study satisfy the essential condition of carrying a thermoremanence. In spite of that, it is shown that there are many factors that can produce undesirable magnetic properties and thus restrict the suitability of these materials for archaeomagnetic analysis. The most important factors influencing the magnetic behaviour during magneto-diagnostic experiments are: the degree of heating in antiquity, the initial composition of the unbaked material and the burial conditions. The large difference in heating temperatures within a particular archaeological feature is a major cause of variation in magnetic behaviour amongst individual specimens, and so preventing a successful pre-selection of specimens for palaeointensity experiments. Nevertheless, the study has shown a very good coincidence between the determined rock-magnetic characteristics and the success rate in palaeointensity evaluation.

We analyse the secular variation captured by the archaeomagnetic field model CALS7K.2 in an effort to determine episodes of eastward and westward motions of Earth's magnetic field at the core-mantle boundary (CMB) over the past 3000 yr. The direction, amplitude and geographical distribution of these motions are described. We find that the clearest azimuthal motions are observed at mid-to high latitudes in the Northern hemisphere, where both eastward and westward motions occur. These azimuthal motions correspond to displacements and distortions of the two main, quasi-stationary, high-latitude magnetic flux patches. Similar motions are not observed in the Southern hemisphere, although this may be a consequence of the poorer data coverage there. The globally averaged drift for the past 1000 yr has been westward since 1400 AD, but eastward between 1000 AD and 1400 AD. In the broad region of the CMB under Europe, the times of transition in the direction of the mean azimuthal motion coincide with the times at which "archaeomagnetic jerks" have been reported. Our results suggest that these are caused by a relatively rapid (< 100 yr) change in the direction of the underlying azimuthal flow near the core surface. We find indications that equatorial westward motions of field features at the CMB, similar to those observed during historical times, may have been present for much of the past 3000 yr. When observed, these low-latitude motions are most prominent in the Atlantic hemisphere, which we interpret as a signature of core-mantle thermal coupling.

- by Christopher Finlay
- •
- Earth Sciences, Geomagnetism, Archaeomagnetism, Magnetic field

Geomagnetic virtual pole positions (VGP's) calculated from archaeomagnetic directional data are compared with three ancient accounts of low latitude observations of the Aurorae boreales, viz. by Aristotle (384-322 BC), Seneca (55 BC-40 AD) and simultaneously by Chinese astronomers in Hangzhou, China and by European observers in Prague in 1138 AD, October 13th.

- by IOANNIS LIRITZIS
- •
- History of Science, Geomagnetism, Archaeomagnetism

The distribution of archaeomagnetic data in eastern Europe and the Near and Middle East shows a remarkable gap in Turkey. This study presents the first archaeomagnetic results from five different mounds in southeast Turkey, the northern part of Mesopotamia. The rock magnetic experiments indicate that in the majority of the samples the dominant magnetic carrier is magnetite, which is stable to heating to temperatures of 700 1C. In general, the demagnetization diagrams are single component and all five sets display well-defined characteristic magnetizations and clustered directions. For the period between 2500 and 700 BCE, the declinations are between 3501 and 201 while inclinations are in the range of 49-641. The directional results are compared with the global geomagnetic field models (CALS7k.2, ARCH3k_cst.1 and CALS3k.4) and the data from the archaeomagnetic database GEOMA-GIA50v2. The results are coherent with both the data and the models except for two nearcontemporaneous sets dating $ 2000 BCE, which are offset to the east by more than 201 with respect to CALS7k.2. Archaeointensity measurements were made using the microwave and conventional thermal Thellier methods applied to five sets of samples (four furnaces and a mud-brick wall). These yielded comparable and intriguing results. While those from the furnaces are slightly higher than the CALS7k.2 model and in agreement with the GEOMAGIA50v2 and the Middle East data, the results from the mud-brick wall suggest a high intensity of 100.8 mT (17.7 Â 10 22 Am 2 ) at $ 1000 BCE. This result is in excellent agreement with recent claims of extremely high intensity measured in other regions of the Middle East for this time period though less consistent with these being associated with extremely short-lived events. Finally, we discuss our new and other recently published archaeointensity results in terms of geomagnetic intensity versus climate.

- by Cor Langereis
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- Archaeomagnetism, Geomagnetic field

Die Viereckschanze auf der "Stierwiese" von Laibstadt im Fränkischen Jura liegt in flachwelligem Gelände auf einem kleinen Plateau eines leicht nach Norden und Osten abfallenden Hanges. Sie gehört zu den obertägig gut erhaltenen Exemplaren dieser Denkmälergattung. Mit ihrer nahezu quadratischen Form, Seitenlängen von 87 bis 99 m (jeweils entlang der Wallmitte gemessen) und Eckwinkeln zwischen 88 und 93 Grad kommt sie dem Idealbild einer spätkeltischen Viereckschanze sehr nahe (Abb. 108). Der Wall ist auf allen vier Seiten, wenngleich stark verflacht und verbreitert, noch mit einer Höhe von bis zu 1,5 m erhal-ten, mit einer Zugangsöffnung in der Mitte des Ostwalls. Die oft beschriebene Überhöhung der Wallecken ist hier noch gut erkennbar, ebenso der im Vergleich zur Umgebung höher gelegene Innenraum der Anlage. Der Graben ist verfüllt und kaum mehr sichtbar, mit Ausnahme der Süd und eines Teils der Westseite, wo eine zeitweise Wasser führende kleine Rinne zu finden ist, die im Süden von einer Baumreihe und einem Feldweg begleitet wird. Die Viereckschanze liegt am Nordfuß des Fränkischen Jura. Der Boden ist gekennzeichnet durch Braunerden und Pseudogleye über lehmigen Doggertonen; er ist vor allem

Abstract Here we report a detailed archaeomagnetic and rock-magnetic study of a pottery kiln from Burgos (Spain) to reconstruct its burning conditions and date its last use and abandonment age. During the course of a rescue archaeological excavation carried out in 2015 in the center of Burgos city, a medieval pottery workshop was discovered. Two well-preserved kilns appeared and archaeomagnetic analyses were performed on one of them. In addition to a large amount of pottery remains, some numismatic and documental evidences provided a general chronological estimation, but the abandonment age of the workshop remains unknown. On the basis of the existing archaeological information we carried out an archaeomagnetic study in order to date its last use. 69 archaeomagnetic samples were collected from the combustion chamber and the kiln's fire tunnel. Stepwise alternating field and thermal demagnetization of the natural remanent magnetization (NRM) were carried out to retrieve the mean direction. Additional experiments consisted in the acquisition of isothermal remanence (IRM), low-field magnetic susceptibility and its anisotropy as well as thermomagnetic curves. Despite the high temperatures expected in the combustion chamber, it appeared that the bricks´ samples from the fire tunnel exhibit the most successful directional results. Magnetite and variable contributions of hematite are the main ferromagnetic minerals observed in the thermomagnetic curves. The type of lithology studied, its previous magnetic history and their location in the kiln strongly condition the observed directional and rock-magnetic results. Additionally, AMS data revealed the manufacturing fabric of the fire tunnel's bricks, showing moderately high anisotropy degrees, but not enough to casts doubts on the directional NRM record. In order to test the reproducibility of the dating results, archaeomagnetic dating was carried out using different geomagnetic field models and the Iberian secular variation curve. The small differences observed in the dating results are mainly due to the density and type of input data of these records. The combination of the archaeomagnetic analyses with the archaeological and documental suggests that last kiln's usage took place during the first half of the XVIth century CE. Overall, this paper illustrates how the combination of archaeological data and archaeomagnetic analyses may improve our understanding about the manufacturing processes, use and age of abandonment of archaeological combustion structures.

- by Ángel Carrancho
- •
- Archaeology, Geology, Geochemistry, Geophysics