Archaeological applications of naturally occurring nanomagnets

Abstract

The ubiquitous presence of iron minerals within the soils and sediments forming archaeological sites can often provide a valuable record of past human activity. These records are formed through the alteration of weakly magnetic minerals to fine grained iron oxides, such as magnetite or maghaemite, that leave an almost indelible magnetic "finger print" on the landscape. Archaeologists have exploited these magnetic records at a variety of levels from geophysical survey to reveal the location of a site, to determining how old a particular excavated feature may be through archaeomagnetic dating. More recent studies have investigated the process of magnetic enhancement through the often complex interaction of pedogenic, microbial and anthropogenic mechanisms and pathways. This research has revealed many unique magnetic signatures within archaeological sediments that may help to identify a range of significant environmental conditions, such as the effects of climate change or the deliberate use of fire. This paper aims to provide an overview of how the techniques of environmental magnetism may be applied to the analysis of archaeological remains. Both field based geophysical prospecting and the measurement of magnetic properties from samples recovered during excavation will be considered. The interpretation of the resulting magnetic measurements will also be addressed through the use of an unmixing algorithm applied to hysteresis data. © 2005 IOP Publishing Ltd.