We propose that plant roots and symbiotic fungi (mycorrhizae) have transported iron from deeper in the regolith to the shallow soil through the process of biolifting. Iron is a plant micronutrient; unlike other mineral nutrients, it is relatively insoluble in aerobic soil solutions. Iron content of the current grassland vegetation was measured and yearly biomass uptake of iron was calculated. When plants decay, the iron is released and forms oxides at shallow depths. The yearly cycling of plant utilized iron in the above ground biomass multiplied by the age of the terrace can account for the shallow iron accumulation in these soils. Preliminary iron isotope measurements indicate that isotopically light iron is enriched in the shallow soils by this process.
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