- DSc, working in the field of geomagnetism and its past secular variations in direction and intensity. Interested in ... moreDSc, working in the field of geomagnetism and its past secular variations in direction and intensity. Interested in dating methods in archaeology. Retired from the National Institute of Geophysics, Geodesy and Geography.edit
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... Studies of Archaeological Samples: Implications for Sample Selection for Paleointensity Determinations Yulong Cui1, Kenneth L. Verosub1, Andrew P. Roberts1 ... text still appears to be a valid indicator for the predominance of MD... more
... Studies of Archaeological Samples: Implications for Sample Selection for Paleointensity Determinations Yulong Cui1, Kenneth L. Verosub1, Andrew P. Roberts1 ... text still appears to be a valid indicator for the predominance of MD grains (Xu and Dunlop, 1995 ... Roberts et al., 1995 ...
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Archaeomagnetic investigation of direction and palaeointensity was carried out on a collection of samples from Neolithic kiln, excavated at Kovatchevo site. Suitability of the materials for obtaining reliable archaeomagnetic results was... more
Archaeomagnetic investigation of direction and palaeointensity was carried out on a collection of samples from Neolithic kiln, excavated at Kovatchevo site. Suitability of the materials for obtaining reliable archaeomagnetic results was checked by applying different rock-magnetic experiments. The obtained values of viscosity index and Koeningsberger ratio show favorable stability characteristics of the burnt clay. The main magnetic minerals, identified by Curie temperature analysis through high-temperature behavior of magnetic susceptibility, and three-axes thermal demagnetization of IRM, show the prevailing role of magnetite and Ti-magnetite. However, investigations on the chemical changes occurring during laboratory heating show overall bad thermal stability of the studied materials, which is not good indication concerning palaeointensity determination. Palaeodirection investigation of samples, taken from different parts of the walls and kiln's floor, reveals possible influence of magnetic refraction - higher Inclination values and azymuthal dependence of Declination for the samples from walls; lower Inclination values from floor's samples. Definitive directional results are determined by averaging data for all samples, which are well distributed all over walls and three kiln's floors. For palaeointensity evaluation rock-magnetic studies are carefully considered and strict acception criteria applied. Archaeomagnetic dating of the studied kiln was performed according to the newly developed method (Lanos, 2001). Final dating, taking into account directional and intensity results, gives the most probable time interval of the last kiln's usage between 5712-5571 BC. Dating result is in agreement with archaeological findings for Bulgarian Early Neolithic and most of 14C data available. This study is supported by EU-funded project AARCH, contract No HPRN-CT-2002-00219 and Mission archeologique de la Vallee du Strymon (Centre de Recherches Protohistorique de l'Universite de Paris).
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Most important task of archaeomagnetic studies is the construction of the geomagnetic field secular variations in the past for a given territory. The obtained reference curves would be precise only when a large number of well-dated... more
Most important task of archaeomagnetic studies is the construction of the geomagnetic field secular variations in the past for a given territory. The obtained reference curves would be precise only when a large number of well-dated archaeological sites from different time periods are included as input data. Sofia Palaeomagnetic laboratory is the first one in the Balkans to accumulate a large number of data spanning the time interval of 3000 BP to 8000 BP. Many archaeological sites in Bulgaria are multilevel settlements with clear stratigraphy. Commonly the prehistoric sites are dated according to the relative chronology, the type of archaeological artifacts found and 14C dates, the latter being not always available. The biggest difficulty is that usually the radiocarbon dates are not well constrained, often contradictory to the vertical stratigraphy. The transformation of conventional 14C dates to absolute dates BC depends a lot on which part of dendrochronological calibration curve...
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Rock magnetic investigations of archaeological materials of burnt clay from Eneolithic ovens (~4500 years BC) showed particular changes with time in the magnetic mineralogy of samples, stored under normal conditions. Our results indicate... more
Rock magnetic investigations of archaeological materials of burnt clay from Eneolithic ovens (~4500 years BC) showed particular changes with time in the magnetic mineralogy of samples, stored under normal conditions. Our results indicate that well-burnt clay from the archaeological materials contains a significant amount of very fine magnetic grains, which could notably influence the rock magnetic properties and behavior at
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Archaeomagnetism is an interdisciplinary branch of geophysics. It is the only approach that examines the variation of geomagnetic field elements in the past. The physical basis of the method is the capability of the fired clay to preserve... more
Archaeomagnetism is an interdisciplinary branch of geophysics. It is the only approach that examines the variation of geomagnetic field elements in the past. The physical basis of the method is the capability of the fired clay to preserve information about the direction and intensity of the Earth's magnetic field in the place and time of its last burning. The information
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The effect of magnetic anisotropy on the palaeointensity results has been evaluated in different materials, including samples from archaeological structures of various ages, such as baked clay from prehistoric domestic ovens or pottery... more
The effect of magnetic anisotropy on the palaeointensity results has been evaluated in different materials, including samples from archaeological structures of various ages, such as baked clay from prehistoric domestic ovens or pottery kilns, burnt soil from ancient fires, and bricks and bricks or tiles used in the kiln’s construction. The remanence anisotropy was estimated by the thermoremanent (TRM) anisotropy tensor and isothermal remanence (IRM) tensor methods. The small anisotropy effect (less than 5%) observed in the palaeointensity results of baked clay from the relatively thin prehistoric oven’s floors estimated previously through IRM anisotropy was confirmed by TRM anisotropy of this material. The new results demonstrate the possibility of using IRM anisotropy evaluation to correct baked clay palaeointensity data instead of the more difficult to determine TRM anisotropy ellipsoid. This is not always the case for the palaeointensity results from bricks and tiles. The anisotr...
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Archaeomagnetic studies in Bulgaria have a long history and the well established secular variation curves of the three elements of the ancient geomagnetic field (declination, inclination and intensity) for the last 8000 years enable the... more
Archaeomagnetic studies in Bulgaria have a long history and the well established secular variation curves of the three elements of the ancient geomagnetic field (declination, inclination and intensity) for the last 8000 years enable the dating of archaeological features of burnt clay, independently of other methods. The determination of ancient palaeointensity is the most difficult characteristic and requires very cautious evaluation of the suitability of the burnt clay material. The present paper is an overview of the methodological progress in studying the suitability of the materials for archaeomagnetic investigations. The main rock-magnetic methods and summary of the most common results are presented involving the archaeomagnetic practice in the palaeomagnetic laboratory in Sofia. In addition, supplementary information obtained by magnetic measurements, which can be helpful for archaeology, are discussed. An example of archaeomagnetic dating procedure is also presented.
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The paper reports the first paleomagnetic study of a Black Sea Quaternary sediment core made by a Bulgarian research group. The experimental results show an important difference in magnetic behaviour between the samples from the Holocene... more
The paper reports the first paleomagnetic study of a Black Sea Quaternary sediment core made by a Bulgarian research group. The experimental results show an important difference in magnetic behaviour between the samples from the Holocene part and those from the Pleistocene part of the core. Suggestions are made for the character of the remanent magnetization and the main carriers
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Archaeomagnetic investigation of direction and palaeointensity was carried out on a collection of samples from Neolithic kiln, excavated at Kovatchevo site. Suitability of the materials for obtaining reliable archaeomagnetic results was... more
Archaeomagnetic investigation of direction and palaeointensity was carried out on a collection of samples from Neolithic kiln, excavated at Kovatchevo site. Suitability of the materials for obtaining reliable archaeomagnetic results was checked by applying different rock-magnetic experiments. The obtained values of viscosity index and Koeningsberger ratio show favorable stability characteristics of the burnt clay. The main magnetic minerals, identified by Curie temperature analysis through high-temperature behavior of magnetic susceptibility, and three-axes thermal demagnetization of IRM, show the prevailing role of magnetite and Ti-magnetite. However, investigations on the chemical changes occurring during laboratory heating show overall bad thermal stability of the studied materials, which is not good indication concerning palaeointensity determination. Palaeodirection investigation of samples, taken from different parts of the walls and kiln's floor, reveals possible influence of magnetic refraction - higher Inclination values and azymuthal dependence of Declination for the samples from walls; lower Inclination values from floor's samples. Definitive directional results are determined by averaging data for all samples, which are well distributed all over walls and three kiln's floors. For palaeointensity evaluation rock-magnetic studies are carefully considered and strict acception criteria applied. Archaeomagnetic dating of the studied kiln was performed according to the newly developed method (Lanos, 2001). Final dating, taking into account directional and intensity results, gives the most probable time interval of the last kiln's usage between 5712-5571 BC. Dating result is in agreement with archaeological findings for Bulgarian Early Neolithic and most of 14C data available. This study is supported by EU-funded project AARCH, contract No HPRN-CT-2002-00219 and Mission archeologique de la Vallee du Strymon (Centre de Recherches Protohistorique de l'Universite de Paris).
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In 1992 (Kovacheva, 1992) we published the updated archaeomagnetic results from Bulgaria for the last 2000 years where it was mentioned that the compilation of data is a continuous process of accumulation of new data and revision of the... more
In 1992 (Kovacheva, 1992) we published the updated archaeomagnetic results from Bulgaria for the last 2000 years where it was mentioned that the compilation of data is a continuous process of accumulation of new data and revision of the previous ones. This is especially true for the old intensity studies considering the newly obtained experimental results of rock magnetic studies
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Research Interests: Geochemistry, Geophysics, Paleomagnetism, Archaeological Science, Geomagnetism, and 15 moreArchaeometry, Byzantine Archaeology, Archaeomagnetism, Palaeomagnetism, Mediterranean archaeology, Archaeomagnetic Dating, Geosciences, Dynamo theory, Archaeological Sciences, Geomagnetic field, Magnetism and Magnetic Materials, Palaeomagnetic Secular Variation, Magnetic Intensities, geomagnetic intensity, and Mediterranean Archaeology and Archaeometry Journal
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The archaeomagnetic intensity reference curve for Western Europe lacks data during the period from 600 to 1000 AD. Baked clay from the walls of a pottery kiln at Reinach (Switzerland), archaeologically dated to the beginning of the 9th... more
The archaeomagnetic intensity reference curve for Western Europe lacks data during the period from 600 to 1000 AD. Baked clay from the walls of a pottery kiln at Reinach (Switzerland), archaeologically dated to the beginning of the 9th century AD, and having a 14C date of 1250±50 BP, was investigated in order to refine the ancient geomagnetic field intensity during
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... Permissions & Reprints. Case study of the Bulgarian Neolithic archaeological site of Piperkov Chiflik and its archaeomagnetic dating. ... Abstract. Baked materials from the Bulgarian Neolithic site of Piperkov Chiflik were... more
... Permissions & Reprints. Case study of the Bulgarian Neolithic archaeological site of Piperkov Chiflik and its archaeomagnetic dating. ... Abstract. Baked materials from the Bulgarian Neolithic site of Piperkov Chiflik were investigated and dated archaeomagnetically. ...
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Bulgarian archaeomagnetic directions and intensities show a satisfactory agreement with those for Ukraine and Paris. Bauer plots of declination against inclination show both clockwise and anticlockwise looping through the last eight... more
Bulgarian archaeomagnetic directions and intensities show a satisfactory agreement with those for Ukraine and Paris. Bauer plots of declination against inclination show both clockwise and anticlockwise looping through the last eight millennia. The necessity for accurate dating of samples studied is stressed.
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ABSTRACT The general aim of archaeomagnetism is to recover the behavior of the ancient geomagnetic field for a given territory using archaeological baked clay structures that have been well-dated by other independent methods. The Sofia... more
ABSTRACT The general aim of archaeomagnetism is to recover the behavior of the ancient geomagnetic field for a given territory using archaeological baked clay structures that have been well-dated by other independent methods. The Sofia Palaeomagnetic laboratory possesses a large data set for the three characteristic geomagnetic field parameters obtained from one and the same material and covering the last 8000 years. The database accumulated by the authors has been updated several times and the greatest difficulty arose for the prehistoric collections, most of which had no radiocarbon or other chronometric dates. Thus as well as methodological archaeomagnetism problems, the main difficulty concerning the construction of reference curves of the variation of the geomagnetic field is related to the distribution of the experimental results over the absolute time scale. This paper examines the similarity between the archaeomagnetic profiles obtained on multilevel tells from the same prehistoric epochs. It would seem that when 14C dates for multilayer tells are missing, the comparison of such archaeomagnetic stratigraphic profiles with the corresponding chrono-stratigraphic reference profile for the same epoch can be useful in verifying their assumed chronology. However, the described peculiarities connected with the multilevel sites results still show some difficulties for the overall estimation of geomagnetic field variations for a given territory.
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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... more
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.
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Recent improvements in archaeomagnetism applied to archaeological baked clay, in France and Bulgaria, are presented in this paper. After reviewing the historical development of the method in France and Bulgaria, and the principles of the... more
Recent improvements in archaeomagnetism applied to archaeological baked clay, in France and Bulgaria, are presented in this paper. After reviewing the historical development of the method in France and Bulgaria, and the principles of the method, we present sampling techniques for in situ structures (kilns and hearths) and sets of displaced materials (bricks or tiles). In the analysis protocol, we stress the importance of correcting the magnetic anisotropic effects especially for bricks. We also show how the problem of brittle specimens can be solved by induration. After a review of the published archaeomagnetic data currently available for France and Bulgaria, we present different smoothing techniques applied to data obtained in these countries. Finally, we present the usage of the variation curves of the geomagnetic elements in the past to calculate the archaeomagnetic dates. One of these techniques is based on a Bayesian approach, similar to the case of the dendro-chronological ca...
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Results from joint work between the Geophysical Institute (Sofia, Bulgaria), and the Geomagnetic Institute (Grocka, Yugoslavia) on the geomagnetic field variation in the prehistoric past are presented. Preliminary curves of variation of... more
Results from joint work between the Geophysical Institute (Sofia, Bulgaria), and the Geomagnetic Institute (Grocka, Yugoslavia) on the geomagnetic field variation in the prehistoric past are presented. Preliminary curves of variation of the three geomagnetic elements: declination, inclination and intensity are presented. The movement of the virtual pole position for the 6500 years time period B.C. is derived. The curves