The Boulder Fields of Mt. Fulufjället, West-Central Sweden

ABSTRACT

Detailed morphological analysis of the boulder fields on the Mt. Fulufjället plateau has revealed three morphologically and genetically different boulder field types; 1/ boulder depressions related to upfreezing in till, 2/ boulder blankets, i.e. glacially transported boulder masses, and 3/ frost-shattered debris in situ. Two distinctly different landscape types are related to the boulder fields of type 1 and 2. At the border between landscape types it can be shown that the boulder depressions and the associated patterned ground were in existence before the last overriding ice sheet, and consequetly are of a pre-Late Weichselian age. The material found in the glacially transported boulder blankets is shown mainly to be derived from boulder depressions. Drawn-out “tails” from boulder depressions are interpreted to be related to lateral shear zones between cold- and warm based zones of the ice sheet. No large-scale periglacial forms appear to have developed on the plateau during the Holocene. An area of more than 60 km² of an interstadial periglacial landscape has survived virtually unchanged despite complete ice cover during the late Weichselian.