Structure, composition and age of the Faeroe basalt plateau

Abstract

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 probabty 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 TiO2. The lower part of the middle formation shows an upward progression from high-Ti olivine tholeiites to high-Ti thoteiites, 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 Sower 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.

The onset of the North Atlantic Igneous Province in a rifting perspective

“…The rifting associated with the bulk of the magmatism in CE Greenland and the Faroe Islands approximately at anomaly 24 (c. 55 Ma) occurred close to the Blosseville Kyst (Larsen & Watt, 1985;Nielsen, 1987;Larsen et al 1999b). This is in accordance with inferences that the magmas of the younger basalt formations of the then neighbouring Faroe Islands were supplied from the north during this period (Waagstein, 1988;Larsen et al 1999b). The onset of final sea-floor spreading at the Blosseville Kyst latitude occurred further to the east along the now extinct AEgir Ridge at c. 54 Ma (Bott, 1985).…”

Understanding the offshore flood basalt sequence using onshore volcanic facies analogues: an example from the Faroe–Shetland basin

“…The sub-volcanic plays here are considered to be prospective and worthy of exploration (e.g. Waagstein, 1988;Laier, Jørgensen & Isaksen, 1997;Ziska & Andersen, 2005), and hence have attracted seismic acquisition over the offshore parts of the lava cover, and drilling in the onshore lava sequence (e.g. Boldreel, 2006).…”

“…Jolley, 2009 and references therein). The lavas are all geochemically tholeiitic, which suggests that their eruption was coincident with a high degree of partial melting of the mantle (Waagstein, 1988). The group consists of seven formations (see Passey & Bell, 2007), of which four formations are composed of significant thicknesses of volcanic rocks ( Fig.…”

“…olivine-phyric suites can be identified geochemically (low-TiO 2 and high-TiO 2 ) (see Waagstein, 1988;Rasmussen & Noe-Nygaard, 1970).…”

“…The Enni Formation is considered to have erupted during magnetic chron C24R (Waagstein, 1988), which places this activity into a cycle of eruptive activity which occurred prior to the opening of the NE Atlantic Ocean.…”