Geophysical Profile Bearing on the Origin of the Jotun Nappe in the Norwegian Caledonides
The Jotun nappe is composed of relatively mafic allochthonous rocks that may have been emplaced by: (1) overthrusting of a rigid plate from a great distance, (2) igneous intrusion, (3) formation of recumbent folds from a near or distant source. A source area for the Jotun nappe has never been demonstrated. A gravity profile shows a positive Bouguer gravity anomaly of about 34 mgal over the Jotun nappe. Gravity interpretation yields models with maximum thickness from 8 to 15 km for a trough-shaped area of the Jotun nappe. The gravity model can be interpreted in terms of an overthrust plate or of locally derived folded nappes similar to the Swiss Alps, but locally derived folded nappes seem to be most consistent with available geological and geophysical data.