. 1984. The nature of smectites in some fine textured lacustrine parent materials in southern Saskatchewan. Can. J. Soil Sci. 64:481494.Detailed mineralogy and chemistry of the clay fraction of five glacio-lacustrine deposits and of one Cretaceous marine shale (Ashville) were studied. Fine clay separates (< 0.2 pr,m) of the five parent materials were predominantly smectite with an average chemical composition: [(Si? 7rAl0 ,E) (Fig. 1)
GHBsne-Eczrnnnren, K. AND sT. AnNeuo, R. J. 1983. carbonate mineralogy of lake sediments and surrounding soils I. Blackstrap Lake. can. J. soil sci. 63 245-257. The carbonate mineralogy of the Blackstrap Lake sediments in central Saskatch-ewan indicates that the lake deposits are composed of carbonatic minerals similar to those found in surrounding soils and glacial deposits. Textural differences reflect the transport of finer materials (silts and clay) from the adjacent eroding landscapes. In particular the persistence of dolomite in the silt fractions of the lake sediment is a good indication that part of the calcite together with the dolomite are derived from surrounding soils. The sediment sand fraction contains appreciable Mg-bearing
MATERIALS AND METHODS
Sediments and SoilsThe lake sediment samples used in this study were obtained from Blackstrap Lake. a water reservoir in a postglacial rivei valley about 35 km southeast of Saskatoon (Fig. 1)
Fine (0.10‐0.25 mm) and medium (0.25‐0.50 mm) sand size fractions of two Boralfs (Gray Luvisols) under Boreal forest were used in this study to characterize the nature of feldspars and the extent of their weathering in glacial till soils in northern Saskatchewan. Feldspars were separated into four different specific gravity fractions by heavy liquids. This facilitated subsequent x‐ray diffraction (XRD) and chemical analyses used for more accurate quantitative determination of feldspars. Distinctive etch pits were observed by scanning electron microscopy. Infilling of voids in the grains by mostly Fe oxides and some clay minerals was observed under the petrographic microscope. While there is evident recent weathering of feldspars within the solum horizons, there is also evidence of ancient weathering as observed in minerals within the parent materials. The studies verified the presence of microcline, orthoclase, and several solid solution series of plagioclase (mostly oligoclase with inclusions of labradorite‐anorthite series). Sodic plagioclases (An 10‐30) were dominant in both profiles, followed by K‐feldspars in Profile 1 and calcic plagioclases (An50‐100) in Profile 3; this confirmed some differences in mineral composition of the two soil parent materials. Stability of feldspars was calculated using a newly developed pedogenic index. As compared to the E horizons, the lower weathering rates in the Bt horizons were attributed to the illuvial clay, which may have played the role of a protective barrier around the feldspar.
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