Soil formation and weathering on ultramafic rocks in the mountainous tundra of the Rai-Iz massif,Polar Urals |
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| Authors: | S N Lesovaya S V Goryachkin Yu S Polekhovskii |
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| Institution: | 1.Faculty of Geography and Geoecology,St. Petersburg State University,St. Petersburg,Russia;2.Institute of Geography,Russian Academy of Sciences,Moscow,Russia;3.Geological Faculty,St. Petersburg State University,St. Petersburg,Russia |
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| Abstract: | Gravelly clay loamy and clayey soils developed from the derivatives of ultramafic rocks of the dunite-harzburgite complex
of the Rai-Iz massif in the Polar Urals have been studied. They are represented by raw-humus pelozems (weakly developed clayey
soils) under conditions of perfect drainage on steep slopes and by the gleyzems (Gleysols) with vivid gley color patterns
in the eluvial positions on leveled elements of the relief. The magnesium released from the silicates with the high content
of this element (mainly from olivine) specifies the neutral-alkaline reaction in these soils. Cryoturbation, the accumulation
of raw humus, the impregnation of the soil mass with humic substances, gleyzation, and the ferrugination of the gleyed horizons
are also clearly pronounced in the studied soils. Despite the high pH values, the destruction of supergene smectites in the
upper horizons and ferrugination (the accumulation of iron hydroxides) in the microfissures dissecting the grains of olivine,
pyroxene, and serpentine, and in decomposing plant tissues take place. The development of these processes may be related to
the local acidification (neutralization) of the soil medium under the impact of biota and carbonic acids. The specificity
of gleyzation in the soils developing from ultramafic rocks is shown in the absence of iron depletion from the fine earth
material against the background of the greenish blue gley color pattern. |
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