The structure of Mellene and Heggberg, Valdres.

Abstract

Structural study of the Valdres Sparagmite and Mellsenn Formation in their type region between the Jotunheim crystalline rocks and the frontal quartzite nappes of the central southern Norwegian Caledonides has revealed that: 1. the Valdres is recumbently folded and allochthonous within a previously unrecognized, major, nappe-salient which was thrust over structurally discordant Ordovician phyllites and Cambrian slates and arenites, 2. elongation lineations trending azimuth 70-145, oblique to the general NE strike of the Caledonides, are parallel to cleavage-bedding intersections and folds axes of first generation bedding folds that have been overturned toward the south and southwest on the southern margin of the salient, 3. the allochthonous Valdres Sparagmite and conformably underlying Mellsenn Formation are overturned in their type section and are, respectively, Eocambrian and Cambrian-Lower Ordovician of different sedimentary facies from rocks of the same age below, 4. the Valdres Sparagmite at two localities was fold-thrusted to its present position along with Precambrian Jotun rocks upon which it was initially deposited. Previous interpretations were that the Valdres Sparagmite is an authochthonous Ordovician-Silurian orogenic deposit derived from early Caledonide tectonic elements and that the elongation lineations are parallel to directions of tectonic transport in nappes.