Measuring the extent of chemical weathering in subarctic alpine environments: Implications for future research

Chemical transformations associated with the weathering of bedrock to regolith, and ultimately to soils are poorly known despite the importance of these transformations in the generation of surface and groundwater solutes, the preparation of bedrock for erosion, the production of plant nutrients, and ultimately the formation of soil itself. This lack of knowledge is particularly apparent in polar and subpolar lands where traditionally chemical processes have been regarded as subordinate to mechanical weathering processes. This paper examines the nature of chemical changes associated with the transformation of bedrock to soil in three subarctic alpine locations by comparing weathering indices calculated from whole-rock chemical analyses of surface soil, regolith, rock fragments, and bedrock. The results of this largely post hoc integration of our previous reconnaissance studies suggests that as bedrock weathers to soil there is a loss of silicon, alkali earths, and alkalis relative to resistant chemical constituents, as might be expected from first principles. However, the loss is not systematic, as bedrock fragments derived from crustal rock represent the most resistant elements of a weathering/soil profile, and surface soils commonly experience eolian addition of chemical constituents. The results of this study are viewed as being “enticing” and suggest a potentially productive line of chemical weathering investigation in polar and subpolar environments that will throw light on patterns of release of chemical constituents in the initial stages of the production of residual soils.