Differential rock weathering in the 'Valley of the Boulders', Karkevagge, Swedish Lapland

摘要

Karkevagge is an alpine valley in the low arctic of Swedish Lapland. It is named after, and famous for, its large deposit of immense (c. 10-15 m) boulders that almost fill the lower valley. Above the boulder deposit, on the flanks of the valley, are more recent and generally much smaller (c. 1-3 m) individual boulders that have fallen from the valley-wall cliff face, presumably from post-glacial valley-side unloading. Some of these smaller boulders are seemingly fresh and unweathered while others have been reduced to no more than mounds in the tundra. These boulders must be younger than the larger, lower giant boulder deposit, but are not particularly recent rockfalls as they are partially buried in colluvium. Comparisons of mineralogy and chemistry indicate that the possibility exists that the incompetent, 'rotten' rocks, if not considerably older than their competent neighbors, are inherently self-destructive. They have evidence of increased sulfur content, which is a proxy for pyrite, a known weathering accelerant in Karkevagge.