The influence of schistocity on soil weathering on, large boulder tops, Karkevagge, Sweden

Weathering and soil development was examined on large boulder tops in Karkevagge, a deglaciated valley in Northern Sweden. Soil and weathered rock was collected from 15 mica-schist, and 5 gamet-mica-schist boulders. The boulders approximated "closed-systems," as their tops were essentially horizontal, and assumed inputs were minimal, with the possible exception of rainwater and aeolian sediment. This provided a relatively uniform sample to determine influential soil-forming factors. Results showed that the soils were shallow, and exhibited minimal horizonation, mostly A over C horizons. Particle size was predominantly coarse sandy loam, with a significant percentage of silt and clay on a number of the boulders. Clay content was higher on the garnet-mica-schist than on the mica-schist boulders. Soil pH was acidic. Deeper soils had developed overlying vertical schisto-city, emphasizing the role of microenvironment. Muscovite, chlorite and mixed-layer minerals were the predominant clay minerals in the boulder soils. Secondary clay formation in soils indicated that chemical weathering was occurring. Results concurred with previous research that chemical weathering is an active geomorphic process in Karkevagge. (C) 2002 Elsevier Science B.V. All rights reserved.