Detailed geophysical investigations of the Stuoragurra postglacial fault, Finnmark, northern Norway.

Abstract

The postglacial Stuoragurra Fault (SF) lies within the Mierujav'ri-Sværholt Fault Zone which is situated in the extensive Proterozoic terrain of Finnmark, northern Norway. It is a southeasterly dipping reverse fault and can be traced fairly continuously for 80 km from Skarrejav'ri south of Masi to Lævnjasjåkka northeast of Iesjav'ri. Detailed geophysical investigations and drilling have been carried out in the Fidnajåkka area 10 km to the south of Masi. The geology of the area is dominated by quartzites. A c. 1 m thick layer of fault gouge detected it the drillholes is thought to represent the actual fault surface. Resistivity measurements reveal low-resistivity zones in the hanging-wall block as well as in the foot-wall block of the SF. These low-resistivity zones lie within a several hundred metre wide belt an are interpreted to be due to fracturing of the quartzites along the regional Mierujav'ri-Sværholt Fault Zone. Within the Fidnajåkka area, however, the resistivity of the hang- ing-wall. block of the SF is typically lower than in the foot-wall, indicating more intense fracturing in the hanging-wall. Vertical electrical soundings show a low-resistivity layer at depth in the eastern hanging-wall block, which corroborates other evidence that the fault dips to the southeast.