Blockfields, old or new? Evidence and implications from some plateaus in northern Norway

Evidence is presented from investigations on plateau-top blockfields in still-glaciated regions of north Norway. Pits dug into these blockfields typically show profile depths > 0.5 m, and sometimes in excess of 1 m. Analysis of fines shows enrichment in the silt and clay sized fraction, suggestive of prolonged chemical weathering. Chemical alteration of parent material is supported by XRD analysis, which identifies a number of clay minerals present in blockfield samples. A chemical weathering origin suggests that these plateau-top blockfields are features which have considerable longevity in the landscape and have been forming since perhaps Tertiary times. The original weathering profiles have been destroyed by frost heaving mechanisms. Protection of the blockfield by cold-based ice occurred during periods of glacial coverage.