Geology of the Båtsfjordfjellet drillcore, Varanger Peninsula, Finnmark, northern Norway

Abstract

Logging of >800 metres of drillcore from a borehole on Båtsfjordfjellet, Varanger Peninsula, revealed a succession of very low-grade, metasedimentary rocks which are assigned to specific Neoproterozoic formations recognisable from regional mapping. The lowest 320 metres of the core consist largely of laminated, maroon to greenish-grey mudstones with thin sandstone beds and some dolomite, characteristic of the Skovika Member of the Båtsfjord Formation. A weak spaced cleavage is present in the mud- and clay-rich lithologies. This pelitic unit is overlain across an inferred unconformity by c.230 m of coarse-grained sandstones with small-clast conglomerates, representing the Sandfjorden Formation of the Løkviksfjellet Group. The upper c. 240 m of the drillcore comprise a repetition of the Skovika Member mudrocks, with the basal contact against the Sandfjorden Formation sandstones marked by a thrust fault which appears to have been reactivated by normal fault movements.