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Soil Science Society of America Journal Abstract -

Mineralogy of Soils Developed on Pliocene-Pleistocene Terraces of the Tombigbee River in Mississippi1


This article in SSSAJ

  1. Vol. 43 No. 3, p. 616-623
    Received: Sept 25, 1978
    Accepted: Jan 18, 1979

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  1. V. E. Nash2



The clay minerology of four soil pedons formed on Pliocene-Pleistocene terraces was investigated. These pedons are in the Typic Hapludult, Typic Fragiudult, Aquic Fragiudult, Typic Ochraqualf subgroups and vary, respectively, in drainage from well drained to poorly drained. Smectite was the major mineral in all of the clay fractions with the maximum quantity usually coinciding with the zone of maximum clay accumulation. Hydroxy Al-interlayered 2:1 clay was generally confined to the upper horizons of these soils. In the deeper horizons, particularly for the poorly drained Aquic Fragiudult and Typic Ochraqualf, the polymeric Al interlayers were replaced by Al(H2O)63+. These soils are all very acid and in the deeper horizons, which are continuously wet, Al-polymers do not form. In cases where hydroxy Al-interlayered minerals were deposited by sedimentation the Al-polymers have been removed. Evidence is presented for a low charge smectite (montmorillonite) and a high charge smectite (beidellite) in these soils. In the surface horizons beidellite is the dominant species with Al-interlayers, however in the deeper zones both types of smectite are found.

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