The Early Carboniferous Magerøy dykes, northern Norway: palaeomagnetism and palaeogeography

Abstract

Palaeomagnetic data from the 337 Ma Magerøy dykes (northern Norway) are of exceptionally high quality, and a positive contact test along with an existing regional result from the Silurian Honningsvåg Igneous Suite attests to a primary Early Carboniferous magnetic signature. The palaeomagnetic pole (S14.8°, E320.1°, dp/dm=4.4/8.6°) is the first Early Carboniferous pole from Baltica, and implies that northernmost Norway–Greenland, the Barents Sea and Svalbard were located at tropical to low northerly latitudes at this time. Northward drift during Carboniferous times (5–6 cm/yr) as demonstrated from palaeomagnetic data is also reflected in the sedimentary facies in the Barents Sea realm, that is, a change from tropical (Early Carboniferous) to subtropical (20–30° N) carbonates and evaporites in the Late Carboniferous. The Magerøy dykes are continental tholeiites which intruded into a set of NW–SE-trending normal faults parallel to the Trollfjorden–Komagelva Fault Zone and the Magerøysundet Fault immediately to the north and south of Magerøya, respectively. These, and many other NW–SE-trending faults (onshore and offshore), were active during Late Palaeozoic extension, and the dykes were probably contemporaneous with the earliest syn-rift sedimentation in the Barents Sea (for example, the Nordkapp Basin).