Fine Particle Translocation in Soils Developed on Glacial Deposits, Southern Baffin Island, N.W.T., Canada

Abstract

Accumulations of fine particles have been observed in coarse-grained, well-drained soils in Arctic areas, and have also been reported in alpine and temperate areas. Both silt caps on cobbles and silt-enriched horizons have been explained as the result of frost sorting. Detailed particle-size analysis of soils from the eastern Canadian Arctic reveals trends which are inconsistent with the frost-sorting hypothesis. In the soil matrix, all particles finer than fine sand show surpluses at some depth. The depth of maximum surplus increases from 15 cm for very fine sand to 55 cm or more for fine clay. The excess clay is offset by deficits higher in the profile, implying redistribution of primary clay. Increases over parent material silt content occur throughout the profiles, implying addition of silt-sized particles to the soil. This surplus of silt is consistent with the addition and infiltration of loess. Both the depths of maximum fine particle accumulation and the amount of accumulated material increase with age, but appear to reach finite limits.

Analysis of silt caps reveals surpluses in all size fractions finer than fine sand at all depths. Excess silt is greatest in silt caps in the upper 20 cm, clay increases are greatest between 40 and 60 cm, and silt caps trend toward parent material composition at depths greater than 60 cm. The distribution of sand within the silt caps also differs from parent material.

The mechanism suggested for particle translocation is illuviation by rain. The interstitial pores in the coarse, noncemented matrix are sufficiently large to allow movement of the observed particle sizes, and rainfalls sufficient to saturate the soil to the depth of coarse silt accumulation have been observed in a 15-yr record. The apparent redistribution of material downward from the surface is the most compelling evidence in favor of illuviation.