Co-Authors:
Singer, M.J., Department of Land, Air, and Water Resources, University of California, Davis, CA 95616, United States
Fine, P., Department of Geology, University of California, Davis, CA 95616, United States
Verosub, K.L., Institute of Soils and Water, Volcani Center, P.O. Box 6, Bet Dagan, Israel
Chadwick, O.A., Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
Abstract:
As the age of the soils in a chronosequence on the California coast increases, the difference between the magnetic susceptibility of eluvial and illuvial horizons increases, and the residual susceptibility after extraction with citrate-bicarbonate-dithionite (CBD) decreases. Enhanced susceptibility results from the conversion of nonferrimagnetic minerals to secondary ferrimagnetic forms (most likely maghemite) and the preferential accumulation of inherited and pedogenic magnetic minerals. Little enhancement occurs for pedons younger than 40,000 yr. By 124,000 yr, most of the magnetic susceptibility can be attributed to forms soluble in CBD. Magnetic susceptibility appears to vary systematically over time for three chronosequences from areas with mean annual precipitation ranging from 650 to 1500 mm yr-1. Magnetic susceptibility enhancement may be a useful parameter for estimating soil age in certain climates. © 1992.