Soil magnetism

Abstract

Although the magnetic properties of soils are seldom if ever quoted in standard texts and few articles on soil magnetism have looked beyond low field susceptibility measurements, a number of authors have pointed to ways in which magnetic measurements can be used in pedology and related fields. Following Le Borgne (1955), several Western and Russian authors have studied the mechanisms whereby magnetic susceptibility (4.4) is often ‘enhanced’ in surface layers. Lukshin et al. (1968) and Vadyunina and Babanin (1972) have shown how susceptibility enhancement is related to major soil formations in the USSR and can be used to give some general insight into the processes affecting iron minerals during pedogenesis, as well as into specific effects such as gleying. The relationships between enhancement mechanisms and lithology (Mullins & Tite 1973), climate (Tite & Linington 1975) and fire (Le Borgne 1960), have received particular attention often through both field observation and experimental study, while recent articles have dealt more directly with the geochemistry of the iron transformations which lead to ferrimagnetic (Section 2.2.4) oxide formation (e.g. Taylor & Schwertmann 1974). Most of the work dealing with instrumentation for soil magnetic measurement has been addressed more or less directly to the use of susceptibility measurements in archaeological prospecting and survey work (e.g. Scollar 1965). The most useful and comprehensive summary of this range of work is the review article by Mullins (1977). In addition, Poutiers’ monograph (1975) illustrates the use of mineral magnetic measurements, in loess and palaeosol studies. More recently, Maher (1984, 1986) has begun to explore the mineral magnetic properties of both contemporary and fossil soils with a view to relating them to soil forming processes.

Even at low concentrations in a soil, iron oxides have a high pigmenting power and determine the color of many soils. Thus soil color, as determined by the type and distribution of iron oxides within a profile, is helpful in explaining soil genesis and is also an important criterion for naming and classifying soils.

Schwertmann, V. and Taylor, R. 1977