Chemical and particle-size evidence for addition of fine dust to soils of the midwestern United States

Significant long-term atmospheric dust additions to soils are well document ed in many parts of the world, but not in the midwestern United States, We investigated elemental mass fluxes associated with soil development in late Wisconsinan loess in Illinois and Minnesota, using Zr as a stable index el ement. Positive mass fluxes of Al, Fe, and Ti can most plausibly be explain ed by additions to these soils of fine far-traveled dust, with higher Al/Zr , Fe/Zr, and Ti/Zr ratios than the coarser locally derived loess. High-reso lution particle-size analyses support this explanation. The proposed dust i nflux will complicate efforts to quantify weathering processes in these soi ls. Far-traveled dust influx could have occurred simultaneously with the fi nal phase of local loess deposition, and/or later, in the Holocene, Dependi ng on the timing of dust influx, many other soils of the region may have be en affected by it.