NJG58-4-03
1978
Basement gneisses mapped as Valdres Sparagmite near Hermansverk, in Sogn, west Norway
58
4
267-272

The Njøs Formation near Hermansverk on the NW side of the Jotunheim Massif has been correlated with part of the Valdres Sparagmite. Evidence is presented from the type-section that these rocks are the deformed representatives of basement gneisses, atfected by varying amounts of cataclasis and recrystallisation, similar to the blastomylonites developed at the base of the Jotunheim Massif. However, their original character as grey quartzo-felspathic gneisses, cut by basic sheets and pegmatite veins, can still be recognised wherever the intensity of the deformation is sufficiently low. The banding previously thought to represent bedding is produced by extreme deformation, which would obliterate the cross-cutting relationships between the various components in such a basement complex, while the feis par porphyroclasts previously considered as evidence for a sedimentary origin in the form of detrital grains are the product of ditferential cataclasis. It is suggested that the Jotun Nappe is underlain by one or more thrust-sheets of basement gneisses, separated from one another by supracrustal rocks of Caledonianan age.

0029-196X
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