Otta-dekket og Valdres-gruppen i strøkene langs Bøverdal og Leirdalen.

Abstract

In his 1951 paper (Strand, 1951) the writer described the Otta nappe (lower Jotun nappe). The nappe was mapped in the Vågå map area, extending west to the meridian 2 dgrs. west of Oslo. It is here a thin and discontinous sheet of mylonitic gneisses, representing the crystalline basement complex of the nappe. In the easternmost part of the area of the map, fig. 2, the crystalline part of the nappe is thicker and here also a part of the sedimentary cover of the nappe has been preserved. Above the Otta nappe are sediments of the Valdres group, developed as a conglomerate with graywacke matrix, the \"Gabbro conglomerate\" of the Valdres group. In the districts further to the west and south-west, along the valleys of Bøvra and Leira, the writer investigated four sections (1-4 in fig. 2) to trace the contiunation of the Otta nappe and the sediments of the Valdres group. The crystalline rocks of the Otta nappe thicken to the west and southwest and reach a thickness of no less than 500 m in section 3. The rocks are amphibolites or saussurite gabbros and gneisses. Almost all the rocks are more or less mylonitized and parts of them have been transformed into fine-grained mylonite schists.