Genesis of magnetic anomalies and magnetic properties of archaeological sediments in floodplain wetlands of the Fossa Carolina

Abstract

Floodplain wetlands are complex systems influenced by many natural and anthropogenic operators. Due to the influence of high and varying groundwater table and high organic contents, geophysical prospection in wetland floodplains quickly reaches the limits of its effectiveness. At the Early Medieval canal Fossa Carolina in southwest Germany, a study design employing magnetometry, drillings, sampling, and in situ rock magnetic measurements was used for environmental magnetic interpretation of magnetic anomalies in magnetograms and sediment layers. This approach offers reliable archaeological interpretation of magnetic anomalies and magnetic properties under the site specific sedimentological conditions of a floodplain wetland. It was also found that man-made magnetic anomalies in the floodplain are due to the genesis of different remanent magnetizations - specifically, greigite (Fe3S4) can cause distinct magnetic anomalies in floodplains that can be recognized readily in surface magnetic data.