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

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Spiers, G. A. Articles by Pawluk, S. Search for Related Content PubMed Articles by Spiers, G. A. Articles by Pawluk, S. Agricola Articles by Spiers, G. A. Articles by Pawluk, S.

Isotopic Evidence for Clay Mineral Weathering and Authigenesis in Cryoboralfs¹

ABSTRACT

Clay mineral distribution and weathering were studied in two Cryoboralf pedons developed on texturally different tills in northeastern Alberta, Canada, to elucidate authigenic mineral formation in these soils. The crystalline clay minerals were identified by x-ray diffraction analyses, and quantified by analyses for cation exchange, surface area and elemental content. The total non-crystalline clay component was determined using selective dissolution treatments. The crystalline clay suite of the parent materials consisted of an admixture of smectites, kaolinite, dioctahedral mica, and chlorite. Beidellite and montmorillonite were both identified as components of the smectite group. Kaolinite was negatively enriched in the E horizons in all clay size separates, whereas mica and smectites were enriched in the Bt horizons as a result of lessivage. Routine chemical and mineralogical characterization suggested apparent neoformation of beidellite in the E horizons of these pedons. As the detrital crystalline clays in these soils are isotopically distinct from any neoformed clay species, the ¹⁸O content of both crystalline and poorlycrystalline clay species was used to explain the observed clay mineral variations within the sola. The ¹⁸O content of the crystalline clay separates indicated the observed inter-horizon variability in content of the individual phyllosilicate mineral species was a result of physical translocation rather than authigenesis. The interpretation of neoformation of beidellite in E horizons was not supported by the ¹⁸O data. Changes in measured ¹⁸O content of clay separates following selective dissolution provided evidence, however, of authigenic poorly crystalline components. Intra-profile variation in the ¹⁸O signature of the authigenic clays is explained in terms of evaporative effects on ¹⁸O enrichment of the soil water.

¹ Contribution from the Dep. of Soil Science, The Univ. of Alberta, Edmonton, Alberta, Canada. T6G 2E3. This contribution comprises partial fulfilment of the requirements for the Ph.D. degree of the senior author.

² Graduate Student, Dep. of Soil Science, Associate Professor of Soil Science, Dep. of Soil Science, Associate Professor of Geology, Dep. of Geology, and Professor of Soil Science, Dep. of Soil Science, respectively, Univ. of Alberta.

Received for publication June 1, 1984. Accepted for publication November 1, 1984.