Coordination and competition between magnetic particles driven by
opposite climate transitions
Abstract
The ferrimagnetic (FM) and antiferromagnetic (AFM) particles of iron
oxides are considered to be pedogenic and climatic indicators in soil
taxonomy and paleoclimate reconstruction due to their enrichment trends
as a function of increasing rainfall and temperature. However, opposite
climate can retard chemical weathering but promote significant
transformation between iron oxides, which could account for a nonlinear
response of magnetism and color to extreme climate. We examined two soil
sequences undergone opposite climate on the eastern edge of the Tibetan
Plateau. The dry and warm climate transition favors the dehydration of
amorphous iron oxides to form AFM hematite and FM particles, while the
wet and cool climate transition impedes the formation but leads to their
competition. The outcome well interprets the synchronous and
asynchronous changes in color and magnetism under extreme opposite
climate, and suggests that evaporation is as important as precipitation
in extreme paleoclimate reconstructions based on iron oxides.