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Abstract
The mineralogy of the clay‐size fraction of 15 samples from cultivated soils was determined using X‐ray diffraction methods. All of the samples contain mica, vermiculite, kaolinite and mixed‐layer minerals, but the proportions of these vary. The regional mineralogic trends are discussed in relation to the possible influences of grain size, relief, sediment‐source variations, time of exposure and climate. The geologic factors are largely related to the geographic distribution of the former glaciomarine, marine and terrestrial environments that successively existed in SW Sweden following the Weichselian glaciation. Although all of these factors have been involved to some extent, there is a tendency for weathering products (kaolinite, vermiculite and mixed‐layer minerals) to be most abundant in areas with greater relief, precipitation and exposure time. However, the grain‐size variations that we documented in this study would directly influence permeability and the intensity of weathering processes at each site, and this seems to best explain the compositional trends. The Lake Vänern basin has, in general, fine‐grained sediments from the late‐stage, shoreline recession. These silty clays have a less‐weathered composition than the coarser‐grained samples from more peripheral areas in Västergötland where greater relief and precipitation are also consistent with the observed mineral‐weathering trends. Although modified and less complete than studies of entire soil‐profiles, the mineralogic and grain‐size information derived from the cultivated soil horizon (Ap) is a valuable complement for both geologic and pedologic modelling.
Stevens, R.L. & Bayard, E., 1994: Clay mineralogy of agricultural soils (Ap horizon) in Västergötland, SW Sweden. GFF, Vol. 116 (Pt. 2, June), pp. 87–91. Stockholm. ISSN 1103–5897.