THE DEPARTMENT OF SURVEY AND EXCAVATION METHODOLOGY OF THE GERMAN ARCHAEOLOGICAL INSTITUTE IN FRANKFURT (original) (raw)
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Physics and Chemistry of the Earth, Parts A/B/C, 2008
The aim of this research was to review the relative merits of different methods of taking samples for archaeomagnetic dating. To allow different methods to be investigated, two archaeological structures and one modern fireplace were sampled in Austria. On each structure a variety of sampling methods were used: the tube and disc techniques of Clark et al. . Developments in archaeomagnetic dating in Great Britain. Journal of Archaeological Science 15, 645-667), the drill core technique, the mould plastered hand block method of Thellier, and a modification of it. All samples were oriented with a magnetic compass and sun compass, where weather conditions allowed. Approximately 12 discs, tubes, drill cores or plaster hand blocks were collected from each structure, with one mould plaster hand block being collected and cut into specimens. The natural remanent magnetisation (NRM) of the samples was measured and stepwise alternating field (AF) or thermal demagnetisation was applied. Samples were measured either in the UK or in Austria, which allowed the comparison of results between magnetometers with different sensitivity.
This paper summarizes the extensive magnetometer survey (over 17 ha) of an important archaeological site in South Bohemia (Czechia). The Late Bronze Age settlement of Bˇreznice has become known for a large amount of specific and at first enigmatic features: trenches, rich in burnt material and structured depositions of finds. Apart from processing by usual methods, magnetometer data has been handled in a less common way in terms of its informative value: as quantitative, spatially continuous information on the intensity of human activities in the landscape. This approach not only led to the definition of the overall extent of the site and detected tens of new trenches, but it also brought information on the functional and behavioural structure of the settlement. The indicated spatial patterns match the model of a continuous growth of individual settlement segments (homesteads) and their gradual shifts following intentional burnings of the buildings. The obtained data represents a significant contribution both to the typology of prehistoric settlements and to the research of their ‘biography’, abandonment rituals and other aspects of prehistoric settlement behaviour. Not least, the data from Březnice demonstrated the information potential of magnetometer data in regard to the formation processes of archaeological sites. The magnetic anomalies were categorized into several groups, some of which can be connected to archaeological features still surviving underground whereas some others may – from the most part – represent the last remains of features, which have been already destroyed in their original setting.
Encyclopedia of Geoarchaeology, 2017
Magnetic prospection was applied for the first time to archaeology in 1956 (Belshé, 1957; Aitken, 1958), and over the years since then, it has become one of the most important archaeological methods for the detection and mapping of buried remains at large archaeological sites (Aitken, 1974; Scollar et al., 1990; Clark, 1996; Neubauer et al., 1998–1999; Benech, 2005; David et al., 2008). Magnetic detection methods are extremely sensitive in the characterization and analysis of iron oxides, much more so than any other form of chemical analysis. Therefore, given a full understanding of the nature of magnetic properties, many details of soil layers and buried archaeological structures can be discovered, visualized, and interpreted only by the “magnetic eye” (Schleifer et al., 2003; Fröhlich et al., 2003; Schleifer, 2004). A complete archaeological interpretation prior to excavation must consider all available archaeological background information as well as surface findings; however, many more crucial details can be derived through a comprehensive soil magnetic analysis, and many new archaeological questions arise from such geophysical prospecting results. For a long time, archaeologists held the firm conviction that geophysical prospecting results on their own would be only of limited use in the resolution of archaeological problems. Today, it has become commonplace that the initiation of a modern archaeological excavation must be preceded by some kind of geophysical prospecting (Schmidt, 2002; Fassbinder, 2007; Aspinal et al., 2008; Fassbinder, 2015a). The great success of magnetic prospection in general is due to the fact that almost all soils of the world show an enhancement of magnetic minerals such as maghemite or magnetite in the topsoil (Le Borgne, 1955, 1960). Except for very rare situations, mostly on sites with dammed-up water and consistent soil wetness, there exist no limiting geological factors precluding the application of magnetic prospecting. Enrichment of these minerals in archaeological soil layers – especially in fireplaces, but also in ditches, pits, or postholes – is caused by the formation of these minerals either by natural or anthropogenic fires, varied pedogenic processes (Taylor et al., 1987), or magnetotactic soil bacteria (Fassbinder et al., 1990; Stanjek et al., 1994). The use of fire, however, plays the major role in the enhancement of magnetic minerals in soils, since this occurs on nearly all sites from the Paleolithic to modern times.
From Magnetic Prospecting to Virtual Archaeology
Monuments and Sites, 2015
Remarkable developments have been made over the last decades in geophysical prospecting for archaeological purposes, beginning in the 1950s with the use of electricity to measure soil resistivity and of magnetics in the form of proton magnetometers (Aitken. 1961, 1974). Until quite recently the use of magnetics in particular had become practically unrivalled through continual improvements involving measuring techniques in the field and procedures for analysis, interpretation and presentation. Milestones included construction of a differential proton magnetometer in the 1960s, automation of digital data collection, electronic processing of the data and finally digital imaging (summarized in Scolarct al. 1990). Building on this work at the Rhenish State Museum in Bonn, at the beginning of the 1980s the author was able to develop caesium magnctometry to the point where it could be used in archaeological prospecting, working first at the Institute for Geophysics at the University of Munich and then at the Bavarian State Conservation Office.
in 6th INTERNATIONAL CONFERENCE ON ARCHAEOLOGICAL PROSPECTION
In order to improve the quantity and above all the quality of the archaeological record, and to both sharpen and broaden the scope of our researches, we established the Laboratory of Landscape Archaeology and Remote Sensing (LAP&T). The aim of the unit is the progressive introduction of remote earth observation systems, along with the enhancement of surface collection techniques through the application of new instruments and methods of data collection and documentation, for both the archaeological and the environmental records. Our approach is conceived as multi-scale, from the macro-environment (the region) through the local environment (the catchments area) to the point-environment (the individual site). We aim to be able to respond with varying degrees of refinement both to matters of conservation and to individual archeological or historical problems of a specifically scientific nature . So far, we have put in train the following approaches: survey and documentation through oblique air photography; high-resolution satellite imagery; historical air photo coverage; large-scale geophysical survey; digital photogrammetry.
GeoScience Engineering, 67(4), 2021
The paper presents the possibilities of specific use of a simple geophysical method in the conditions of an ongoing archaeological excavation. It demonstrates an effective (i.e., quick, inexpensive, and beneficial) method that greatly enhances the knowledge gained from archaeological context analysis and thus contributes to a more accurate interpretation of the excavated portion of the historic strata. For example, field measurements of magnetic susceptibility can help to correctly interpret the genesis of individual layers, to distinguish individual phases in a visually indistinguishable stratum, or to indicate layers (and stone walls) that have undergone heating, etc. A detailed geophysical measurement of magnetic susceptibility was carried out on a section with archaeologically excavated relics of fortifications on the outskirts of the early medieval Mikulčice – Valy hillfort and the results were then critically confronted with the archaeological interpretation. This mutual multidisciplinary approach is also methodologically significant. Geophysics reveals certain information that is invisible to the archaeologist's eye, and may provide important clues to the correct interpretation of the archaeological context. Archaeological research, in turn, provides more precise information on the reasons and possible source of changes in magnetic susceptibility values of different layers and materials.
Validity of archaeomagnetic field recording: an experimental pottery kiln at Coppengrave, Germany
Geophysical Journal International, 2016
Palaeomagnetic data obtained from archaeological materials are used for reconstructions of the Earth's magnetic field of the past millennia. While many studies tested the reliability of this recorder for palaeointensity only a few studies did this for direction. The study presents an archaeomagnetic and rock magnetic investigation applied to an experimental pottery kiln, which was operated in 2003 to produce stone ware. This kind of high-quality pottery needs a temperature of at least 1160 • C. Shortly before heating of the kiln direct absolute measurements of the absolute geomagnetic field vector have been carried out close to it. After cooling of the kiln 24 oriented palaeomagnetic samples have been taken. Although Curie temperatures are about 580 • C, that is the typical temperature for magnetite, thermal as well as alternating field demagnetisations reveal also a considerable amount of hematite as magnetic carrier. This mixture of magnetite and hematite is dominated by pseudo-single domain grains. Demagnetisation removed in some cases weak secondary components, but in most cases the specimens carried a single component thermoremanent magnetisation. The mean characteristic remanent magnetisation direction agrees on 95 per cent confidence level with the directly measured field direction. Archaeointensity was obtained from five specimens with the Thellier-Coe method and with the multiple-specimen palaeointensity domain-state corrected method. Six of these specimens also provided a result of the Dekkers-Böhnel method, which overestimated the archaeointensity by about 9 per cent compared to the direct value, while after correction for fraction the value agrees very well. For the multiple-specimen palaeointensity domain-state corrected method only fractions between 25 and 75 per cent have been used and specimens showing alteration have been excluded. Above 450 • C many specimens showed alteration of the magnetic grains. Because median destructive temperatures were often above this value in most cases the fraction was less than 50 per cent. Nevertheless the obtained intensity (48.48 ± 0.24 µ) is on 95 per cent confidence level in agreement with the direct observation. Behaviour of the specimens during the Thellier-experiments was not ideal because of narrow unblocking temperature spectra and alteration. Nevertheless, the obtained mean archaeointensity is also in agreement with the direct field observation. Here the relative palaeointensity error is about 6 per cent and very high compared the multiple-specimen palaeointensity domain-state corrected method. The investigation demonstrates that a pottery kiln can provide a very precise estimate of the ancient geomagnetic field vector.