HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Rivers, J. M. Articles by Doll, W. E. Search for Related Content PubMed Articles by Rivers, J. M. Articles by Doll, W. E. GeoRef GeoRef Citation Agricola Articles by Rivers, J. M. Articles by Doll, W. E. Related Collections Redox Processes Remote Sensing Soil Physics

Investigation into the Origin of Magnetic Soils on the Oak Ridge Reservation, Tennessee

^a Environmental Sciences Division, Oak Ridge National Lab., P.O. Box 2008, Oak Ridge, TN 37831-6038
^b Jr., Geology Dep., Temple Univ., 1901 N. 13th St., Beury Hall, Philadelphia, PA 19122-6081

View larger version (42K): [in a new window]   Fig. 1. A photograph of the third core tube extracted from the area within the magnetic anomaly with soil horizon characteristics and volume magnetic susceptibility. A horizons were often readily identifiable by a poorly consolidated clay matrix with grass roots, high chert content (probably due to deflation) and angular peds. A well-consolidated clay matrix with subangular or more often columnar peds characterized CBw-horizons, which generally lacked roots and chert.

View larger version (47K): [in a new window]   Fig. 2. X-ray diffraction analysis of the (A) sand fraction and the (B) silt fraction from the magnetic and nonmagnetic soils. Hematite peaks can be seen in all samples while maghemite peaks are only present in the magnetic samples. Both the magnetic and nonmagnetic samples are rich in quartz and kaolinite.

View larger version (15K): [in a new window]   Fig. 3. X-ray diffraction analysis of magnetically separated grains from the sand fraction of the magnetic soil (vertical axis is intensity [CPS]). While difficult to distinguish, this analysis shows peaks more characteristic of maghemite than magnetite. The magnetic grains are aggregates of both maghemite and hematite. (D-spacing labeled on peaks [nm].)

View larger version (19K): [in a new window]   Fig. 4. Composite diagram of the top five core sections extracted from within a magnetic anomaly showing horizon changes and magnetic susceptibility. Magnetic susceptibility tends to peak near the A/CBw boundaries, where redox conditions most favored the formation of maghemite.

View larger version (66K): [in a new window]   Fig. 5. (A) Scanning electron microscopy image and (B) energy dispersive x-ray analysis of a magnetic particle separated from the soil core, which was typical of others studied. Energy dispersive x-ray data showed this particle by an iron oxide, not greigite. This particle is too large to be fly ash or to be the product of iron biomineralization by magnetotactic or dissimalatory bacteria. The shape is inconsistent with magnetotactic crystals, which are usually cubic or octahedral, and more rarely prismatic, tooth, arrowhead, and bullet-shaped. Vertical axis is in CPS.

View larger version (83K): [in a new window]   Fig. 6. Airborne magnetic anomalies (magenta) overlain on topographic data. The magnetic anomalies are found in depressions on Copper Ridge. These depressions reflect dolines (sinkholes) on the ridge in which Fe rich sediments have collected. The dolines are often oriented perpendicular or parallel to the strike of Copper Ridge suggesting an association with joints in the bedrock. Data in the white area (center) was omitted due to magnetic interference from buildings. The black dot marks the magnetically anomalous area from which the more magnetic soil core was extracted. The less magnetic core was extracted outside the same anomaly.