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Accueil du site → Master → Etats Unis → 1973 → The pedogenic alteration of acicular clay minerals on the semiarid Texas High Plains

Texas Tech University (1973)

The pedogenic alteration of acicular clay minerals on the semiarid Texas High Plains

Bigham, Jerry M

Titre : The pedogenic alteration of acicular clay minerals on the semiarid Texas High Plains

Auteur : Bigham, Jerry M

Université de soutenance : Texas Tech University

Grade : Master of Science (MS) 1973

Résumé
Sepiolite and attapulgite (palygorskite) are acicular, hydrous magnesium silicates that may contain substantial quantities of substituted iron and aluminum. Although they appear to be geographically dispersed, sepiolite and attapulgite remain as relatively uncommon silicate clay minerals. In addition, most reported occurrences have been of geological rather than of pedological significance. Their absence or degraded state in most soils, even soils developing from geologic materials rich in one or both of these minerals, would suggest a rather high susceptibility to chemical and physical alteration by weathering processes. Therefore, the primary objectives of this study were (a) to determine the natural alteration products of sepiolite and attapulgite under botli field and laboratory conditions and (b) to characterize as completely as possible the chemical environment under which these minerals are stable (or unstable) in soils. A secondary objective was to supplement current knowledge regarding tlie geographic distribution of sepiolite and attapulgite on the Llano Estacado. A total of five soils, developing from varied geologic materials and expressing as much pedological development as possible, were sampled for detailed study. No particular soil types were preferentially chosen, but, prior to their selection, the soils were required to display homogeneous lithologies and to contain substantial quantities of an acicular mineral in the lower portions, at least, of their profiles. The conclusions of this study are based upon both field observations and laboratory data, and it is hoped that the information obtained will prove useful in understanding the genesis and mineralogy of certain soils that may be relatively common to this and other arid and semiarid regions of the world.

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