Rates of Magnetic Enhancement in Loessic Soils Estimated From Profiles of Rapidly Eroding Soils (Invited)
Abstract
The rate of magnetic development of soils is highly debated. Studies of recently disturbed soils claim that most magnetic enhancement is completed within a few few hundred to 1000 years, while studies of soil chronosequences and paleosols conclude that soil development and associated magnetic enhancement can span hundreds of thousands of years. We combine measurements of erosion rates and magnetic susceptibility profiles to estimate the rates of magnetic enhancement for loessic soils in the Midwestern United States. We have measured soil erosion rates at 24 sites and sampled over thirty soil profiles at Hitchcock Nature Area in the loess hills of western Iowa. Soil erosion rates on steep slopes vary between approximately 0.5 mm/year for well vegetated sites and 5 mm/year for bare ground. Assuming that the rate of magnetic enhancement is highest in the topsoil and decreases exponentially with depth we estimated magnetic susceptibility enhancement rates of 3 ± 1 × 10-9 m3kg-1a-1for three soil profiles along a very steep loess ridge. Assuming that these enhancement rates have at least regional validity the magnetic properties of well developed soils nearby would form over several hundreds but not thousands of years.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMGP41C..07G
- Keywords:
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- 0486 BIOGEOSCIENCES / Soils/pedology;
- 1512 GEOMAGNETISM AND PALEOMAGNETISM / Environmental magnetism;
- 1540 GEOMAGNETISM AND PALEOMAGNETISM / Rock and mineral magnetism;
- 1826 HYDROLOGY / Geomorphology: hillslope