The origins of the ultrafine pedogenic component responsible for the magnetic susceptibility enhancement is an unsolved problem of great importance, because this component represents the link between the magnetic signal and paleoclimate. Some authors propose multiple origins that include formation via inorganic pathways and by magnetite-producing bacteria. Maher and Thompson [1992] found that the ultrafine ferrimagnetic component consists of two types, one that resembles soil magnetite produced by inorganic precipitation, and the other that resembles magnetite found in magnetotactic bacteria.
The chemical approach by Fine et al. [1993], showing
the transformation of iron in the loess column, yields insight
into the problem. In the Chinese loess sequences, they found
that each paleosol had more total iron (Fe
) and more iron
removed by CBD (Fe
) than its parent loess and that the
increase of Fe
was relatively greater than that of Fe
.
This observation indicates that iron in detrital grains had been
transformed to secondary iron oxides during pedogenesis.