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This article in SSSAJ

  1. Vol. 44 No. 1, p. 159-167
    Received: Jan 31, 1979



Pedogenic Degradation of Sepiolite and Palygorskite on the Texas High Plains1

  1. J. M. Bigham,
  2. W. F. Jaynes and
  3. B. L. Allen2



The acicular (needle-like) clay minerals, sepiolite and palygorskite, were found to be widespread in late Cenozoic sediments of the Texas High Plains. Five soils developed in these sediments, or in materials derived thereform, were analyzed to determine if sepiolite and palygorskite were stable under soilforming conditions. X-ray diffraction, cation exchange capacity, and electron optical data indicated that degradation of these minerals accompanied soil formation. Soil reaction values and water-soluble Mg were found to decrease with proximity to the soil surfaces and total chemical analyses of carbonate-free clays (< 0.2 µm) from two profiles showed similar losses of structural Mg and Si. Since sedimentary sepiolite and palygorskite are Mg-silicates formed under alkaline conditions, reduced OH and Mg activities probably contributed to the instability of these minerals within the specified soil environments.

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