Enrichment of the ferrimagnetic minerals magnetite and maghemite is frequently observed in the top layer of soil horizons. Although both inorganic and organic processes are known to produce magnetite, magnetite in soils has been ascribed to an inorganic origin. We report here the discovery of living magnetic bacteria, similar to those found in salt- and fresh-water sediments, in the A horizon of a well developed soil profile in a typical meadow environment in southern Bavaria. The bacteria were detected in fresh samples using an optical microscope equipped with a rotating magnetic field and a volumetrically calibrated depression slide, permitting accurate counts of the volume density of the organisms. We suggest that magnetic bacteria and their magnetofossils can contribute to the magnetic properties of soils.

The launch of the first German radar satellite TerraSAR-X in 2007 opened a new era in spaceborne radar remote sensing. So far the applicability for the high-resolution prospection of upstanding and, especially, buried monuments was limited because of the low resolution of the former sensors. TerraSAR-X, however, provides us with images with a spatial resolution of up to 1 m. The satellite operates in the so-called X-band with a frequency of 9.65 GHz. Therefore it is supposed that there is no possibility to penetrate the soil with this sensor. To testify and analyse the benefit of TerraSAR-X in archaeological geophysics, we chose as a test site a Roman fortress in Syria. The site was chosen as we already have GPR data of the same area for a comparison and for the verification of the actual penetration depth. Our results revealed that it is possible to resolve superficial and even buried structures in the data set, which provides evidence that the X-band waves can penetrate the soil. This paper shows our results of the survey and an estimation of the possible penetration depth of TerraSAR-X. Copyright

The occurrence of greigite (Fe3S4) in soils is reported for the first time. It forms irregularly-shaped aggregations within plant cells in the Gr2 horizon of a gley soil developed from colluvial material. Greigite was identified by X-ray diffraction and magnetic measurements and was investigated by optical and transmission electron microscopy. Biogenic formation is proposed, based on the elongated shape of single greigite crystals, and sulphur isotope analyses, which showed a depletion in 34S relative to the soil-water sulphate. The cell-edge length of 0.98639 f0.00003 nm is significantly smaller than values reported for sedimentary greigite. The mean coherence length of 27nm agrees with TEM observations and indicates that the single greigite crystals lie in the superparamagnetic region. However, the fine aggregates show magnetically single-domain behaviour. Greigite is the only carrier of a stable magnetic remanence in the soil profile studied.

Magnetic measurements were performed on soil samples, which contained bacterial greigite. The greigite‐containing soil horizon is characterized by SIRM/χ > 70 kA m−1 and by Q‐factors >5. Alternating field (AF) demagnetization curves of the NRM gave stable directions. According to IRM acquisition and alternating field demagnetization of the IRM and ARM, the greigite in bulk soil samples shows single domain behaviour. This SD behaviour is also confirmed by hysteresis and by frequency‐dependent susceptibility measurements. The thermomagnetic behaviour was checked on extracted greigite. The magnetic parameters of soil greigite are compared with parameters of sedimentary greigite and of bacterial magnetite.

The Roman Limeswith alength of 550 kmisthelargest archaeologicalsite of Europe aswellasthelargest monument of the Roman period. In July 2005 it was decided that the Limes and its interrelated archaeological sites, together with Hadrian's Wall in England, would be a component of a 'Trans-National World Heritage Site' taking the name 'Frontiers of the Roman Empire' . From that point it was necessary to minimize and/or to avoid archaeological excavation. Further research on such sitesismainlylimitedtotheapplicationofnon-destructivetechniques.Amongothergeophysicaltools, magnetometry, based on the rock magnetic knowledge turned out to be a highly suitable method. Two examples that allowed verification and completion of old maps of the Reichs-Limes-Kommission will be shown here; these projects exemplify geophysical work on the Bavarian Limes. At the site of Oberhochstatt we discovered the exact location and determined information on the size and orientation of the fort that previous searches for a long time had failed to find.At Theilenhofenwe were ableto completethemap ofthe whole fort withallfortification ditchesandthe water supply, toverify the troopleveland to confirm the former fort onwhichis superimposed the traces ofthe Roman vicus