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... Despite skepticism about the veracity of excursions and their use as stratigraphic markers (Merrill and McFadden, 2005), improved sampling of marine sediments deposited at high rates and precise geochronology applied to both sediments... more
... Despite skepticism about the veracity of excursions and their use as stratigraphic markers (Merrill and McFadden, 2005), improved sampling of marine sediments deposited at high rates and precise geochronology applied to both sediments (astrochronology) and lava flows ( 40 ...
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The early medieval site Thunau am Kamp consists of a hill fort and a settlement with large burial ground at the bank of river Kamp. All these features are under archaeological investigation since many years. The settlement comprises many... more
The early medieval site Thunau am Kamp consists of a hill fort and a settlement with large burial ground at the bank of river Kamp. All these features are under archaeological investigation since many years. The settlement comprises many pit houses, some with stratigraphic order. Every pit house was equipped with at least one cupola oven and/or a hearth or fireplace. Sometimes the entire cupola was preserved. The site was occupied during the 9th and 10th AD according to potshards which seem to indicate two phases: In the older phase ovens were placed in the corner of the houses while during the younger phase they are found in the middle of the wall. In order to increase the archaeomagnetic data base 14 ovens have been sampled. They fill the temporal gap in the data base for Austria around 900 AD. Laboratory treatment included alternation field and thermal demagnetisations as well as rock magnetic experiments. The baked clay with was formed from a loess sediment has preserved stable directions. Apart from one exception the mean characteristic remanent magnetization directions are concentrated around 900 AD on the early medieval part of the directional archaeomagnetic reference curve of Austria (Schnepp & Lanos, GJI, 2006). Using this curve archaeomagnetic dating with RenDate provides ages between 800 and 1100 AD which are in agreement with archaeological dating. In one case archaeomagnetic dating is even more precise. Together with the archaeological age estimates and stratigraphic information the new data have been included into the database of the Austrian curve. It has been recalculated using a new version of RenCurve. The new data confine the curve and its error band considerably in the time interval 800 to 1100 AD. The curve calibration process also provides a probability density distribution for each structure which allows for posterior dating. This refines temporal errors considerably. Usefulness of such an approach and archaeological implications will be discussed.
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Research Interests: Archaeology and Geology
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Determination of geomagnetic paleointensity by the Thellier method compares the decay of natural remanent magnetisation with the gain of a laboratory induced thermoremanent magnetisation. If fragile samples lose some amount of their... more
Determination of geomagnetic paleointensity by the Thellier method compares the decay of natural remanent magnetisation with the gain of a laboratory induced thermoremanent magnetisation. If fragile samples lose some amount of their material after each heating step, the Thellier experiment will be systematically disturbed and paleointensity will be over-estimated. For a lost of 5% of the sample’s mass an over-estimate
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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... more
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. (Clark, A.J., Tarling, D.H., Noel, M., 1988. 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.The tubes and plastered hand block specimens showed good agreement in directional results, and the samples obtained showed good stability. The discs proved to be unreliable as both NRM and the characteristic remanent magnetisation (ChRM) distribution were very scattered. The failure of some methods may be related to the suitability of the material sampled, for example if it was disturbed before sampling, had been insufficiently heated or did not contain appropriate magnetic minerals to retain a remanent magnetisation. Caution is also recommended for laboratory procedures as the cutting of poorly consolidated specimens may disturb the material and therefore the remanent magnetisation. Criteria and guidelines were established to aid researchers in selecting the most appropriate method for a particular archaeological structure.
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Research Interests: Geography, Geology, Geophysics, Mineralogy, Western Europe, and 15 morePaleomagnetism, Rock magnetism, Archaeomagnetism, Magnetic field, Iron Age, Archaeomagnetic Dating, Reference Data, Geomatic Engineering, Geomagnetic field, Success Rate, Geophysical, Palaeomagnetic Secular Variation, Kiln, Declination, and Secular Variation
Volcanic records of excursional geomagnetic field behavior, in particular paleointensity estimates, are fragmentary for the Pleistocene. The West Eifel volcanic field is unique in that 12 of 66 measured lava flow sites record Virtual... more
Volcanic records of excursional geomagnetic field behavior, in particular paleointensity estimates, are fragmentary for the Pleistocene. The West Eifel volcanic field is unique in that 12 of 66 measured lava flow sites record Virtual Geomagnetic Poles (VGPs) clustered between 34 to 45° N and 30 to 50° E (over Iraq). Paleointensities of 37 lavas reveal that 9 transitionally magnetized and
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The data base of geomagnetic palaeointensities obtained from archaeological artefacts is poor and very scattered for Western and Central Europe. High precision palaeointensities have been determined from a single archaeological site in... more
The data base of geomagnetic palaeointensities obtained from archaeological artefacts is poor and very scattered for Western and Central Europe. High precision palaeointensities have been determined from a single archaeological site in Lübeck (Germany) where a sequence of 25 bread-oven-floors has been preserved in a bakery from medieval times until today. Age dating confines the time interval from about 1300 AD to about 1750 AD. Palaeomagnetic directions have been determined from each oven-floor (Schnepp et al., JGR, 2003). Palaeointensity was measured from selected specimens with the double-heating Thellier method and reliable palaeointensity results have been obtained. Tests for thermoremanent magnetisation anisotropy have been performed, but did not show a significant change, while a cooling rate correction was not necessary. 22 mean palaeointensity values derived from the oven-floors show maxima in the 15th and early 17th century AD, followed by a decrease of palaeointensity of about 25% until 1750 AD. The Thellier experiments provided also new characteristic remanent magnetisation directions which were included in the data set. Mean directions have been recalculated. Palaeointensity together with the directions represent a record of about 450 years full vector secular variation. From this full vector data set a secular variation curve has been calculated using a Bayesian modelling taking dating errors, all errors on the field vector and stratigraphy into account. A smooth curve with an error envelope was obtained which compares very well with the gufm1 geomagnetic model (Jackson et al., Phil. Trans. R. Soc. Lond. A, 2000) obtained from historical observations starting at 1600 AD. Comparison of the marginal curve obtained for palaeointensity with a selected data set of archaeomagnetic intensities from Western and Central Europe will be discussed.
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Additional file 1: Table S1: Paleointensity results on specimen level.
Additional file 5: Figure S1: κ(T)-curves (left) and thermal cycling (right). The κ(T)-curve type is given (see text). One representative example for each type from each site (cf. Table 1 and S3) is shown.
Additional file 7: Figure S3: Histograms of MDT (top) and MDF (bottom) for the Steinberg site (left) and the Klöch site (right).