Structure, composition and age of the Faeroe basalt plateau

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Abstract
Summary: The lower Tertiary Faeroe basalt plateau is centred around the Faeroe Islands in the northern part of the supposed Faeroe-Rockall microcontinent. It consists of subaerial lavas, divided into three formations. The lower formation is probably thickest (>3 km) in the southern or central part of the islands, whereas the middle and upper formations are probably thickest (> 2 km in total) just N of the Faeroes, close to the line of opening between the Faeroes and Greenland. The lower formation consists of tholeiites relatively low in TiO 2 . The lower part of the middle formation shows an upward progression from high-Ti olivine tholeiites to high-Ti tholeiites, whereas the entire upper and rest of the middle formations consists of a contrasting population of high-Ti tholeiites and low-Ti MORB-like olivine tholeiites to tholeiites. The MORB type is confined to the northern Faeroes, increasing in abundance upwards. Similar MORB-like basalts have been recovered from further SW along the microcontinent (Faeroe Bank, Bill Bailey Bank, Lousy Bank and the Rockall Plateau), being associated with high-Ti tholeiites near the Faeroes and away from the Tertiary line of opening (Faeroe and Bill Bailey Banks). In addition, transitional to mildly alkaline basalts have been recovered on the E side of the Faeroe Bank Channel and on Bill Bailey Bank. Based on field revision of the magnetostratigraphy of the lower formation it is tentatively suggested that the lower formation was extruded during chrons C26R to C25N and the two higher formations during C24R. Accumulation rates seem to have varied systematically and to have been related to the abundance and type of sediments between the lavas, which may indicate that extrusive activity ceased in the Faeroes before the opening of the NE Atlantic in C24R, and explain the presence of conjugate strike-slip faults in the NW Faeroes. The spatial distribution of the various basalt types fits a model of shifting axes of intraplate volcanicity, shifting from the Faeroes to E Greenland and in part back again.