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- Title
Investigation into the Origin of Magnetic Soils on the Oak Ridge Reservation, Tennessee.
- Authors
Rivers, John M.; Nyquist, Jonathan E.; Roh, Yul; Terry Jr., Dennis O.; Doll, William E.
- Abstract
In 1993–1994, researchers at Oak Ridge National Laboratory collected high-resolution airborne geophysical data on the Oak Ridge Reservation, Oak Ridge, TN. The data were collected in part to address concerns about possible undocumented hazardous waste sites. Interpretation of the aeromagnetic data was complicated, however, by the discovery in remote areas of numerous small magnetic anomalies of natural origin. Magnetic susceptibility measurements of core showed that the underlying Copper Ridge Dolomite was non-magnetic. We attribute the magnetic anomalies to the presence of the ferromagnetic mineral maghemite (γ-Fe2O3), which formed during pedogenesis of Fe-enriched colluvium that had infilled low-lying areas, including dolines. We discuss explanations offered in the literature for the formation of magnetic soils, and present evidence based on profile descriptions, thin sections, x-ray diffraction (XRD), and scanning electron microscopy (SEM), that in this case, maghemite formed either by anaerobic microbial Fe reduction followed by the formation of single-domain maghemite, or by abiological weathering and reduction of an Fe-bearing mineral followed by oxidation. Naturally occurring magnetic soils may produce magnetic anomalies similar to those characteristics of anthropogenic objects, such as buried waste drums, and complicate interpretation of airborne geophysical surveys.
- Subjects
TENNESSEE; UNITED States; SOIL mineralogy; SOIL composition; MAGNETIC properties; MAGNETISM; ELECTROMAGNETISM
- Publication
Soil Science Society of America Journal, 2004, Vol 68, Issue 5, p1772
- ISSN
0361-5995
- Publication type
Article
- DOI
10.2136/sssaj2004.1772