The structural history of the northwestem margin of the Jotunheimen Massif

The Jotunheimen Massif tectonically overlies a thrust-sheeted succession of metamorphosed sedimentary and volcanic rocks along its north-western margin. Five phases of Caledonian deformation are recognizable in this succession and in the marginal Jotun rocks which, in addition, preserve evidence of a complicated Precambrian tectono-metamorphic history. Cleavage development and minor folding characterized each Caledonian deformation, whilst major folds were formed only during the third and fourth episodes. Thrusting occurred on at least three occasions but the major period of thrusting, responsible for the emplacement of the massif, was associated with the D1 and D2 deformations when tectonic movements were directed towards the southeast. Compelling evidence in support of this view includes the D1 and D2 facing directions, the regional sense of vergence implied by the angle between the S1 and S2
cleavages, the D1 thrust geometries and the layer drag associated with some of these thrusts.