Holocene microweathering rates and processes on ice-eroded bedrock, Røldal area, Hardangervidda, southern Norway

Abstract

Abstract Post-glacial weathering of ice-eroded metamorphic bedrock was investigated in the Røldal area (60°N) of the Hardangervidda Plateau in southern Norway. Quartz veins were used as reference surfaces to determine a mean post-glacial surface lowering rate of 0.55 mm ka −1 . Chemical characteristics of late-season runoff were determined for one catchment (Snøskar) and a chemical erosion rate of 4.9 t km −2 a −1 was obtained. A mean in situ fracture enlargement due to microweathering of 0.12 mm ka −1 was also determined. These rates are low, although comparable with similar environments in cold regions, and suggest that microweathering has had relatively little impact on Holocene landscape evolution. Weathering rind thickness was found to be less on fracture walls than on exposed bedrock surfaces, suggesting fractures have not played a significant role in microweathering. Observations of weathering morphology reveal a range of forms including shallow spalling, tafoni and pseudokarren, indicating locally intense weathering activity. Analysis of interrelationships between multiple weathering indices points to the importance of bedrock microweathering as a precursor to macro-breakdown and landform evolution. The research reasserts the importance of chemical activity in cold environments and the importance of moisture supply for effective microweathering.