The stratigraphy and structure of the Faroese continental margin

Abstract

This paper presents a summary of the stratigraphy and structure of the Faroese region. As the Faroese area is mostly covered by volcanic material, the nature of the pre-volcanic geology remains largely unproven. Seismic refraction data provide some indications of the distribution of crystalline basement, which probably comprises Archaean rocks, with the overlying cover composed predominantly of Upper Mesozoic (Cretaceous?) and Cenozoic strata. The Cenozoic succession is dominated by the syn-break-up Faroe Islands Basalt Group, which crops out on the Faroe Islands (where it is up to 6.6 km thick) and shelf areas; post-break-up sediments are preserved in the adjacent deep-water basins, including the Faroe-Shetland Basin. Seismic interpretation of the post-volcanic strata shows that almost every sub-basin in the Faroe-Shetland Basin has been affected by structural inversion, particularly during the Miocene. These effects are also observed on the Faroe Platform, the Munkagrunnur Ridge and the Fugloy Ridge, where interpretation of lowgravity anomalies suggests a large-scale fold pattern. The structure of the Iceland-Faroe Ridge, which borders the NW part of the Faroe area, remains ambiguous. The generally thick crust, together with the absence of well-defined seawards-dipping reflectors, may indicate that much of it is underlain by continental material.

The Iceland Microcontinent and a continental Greenland-Iceland-Faroe Ridge

“…• The Faroe Islands are underlain by continental crust topped by > 6 km of basalt [Bott et al, 1974;Ólavsdóttir et al, 2017]. Seismic data from the eastern part of the Iceland-Faroe Ridge detect stretched continental crust similar to that underlying the Rockall Bank where HVLC has been interpreted as inherited continental crust of Palaeo-European affinity [Bohnhoff & Makris, 2004].…”

“…• Paleocene (~63 -56 Ma): The pre-breakup rifting phase (late Danian-Thanetian) was characterized by formation of a series of sag and fault-controlled sub-basins [Dean et al, 1999;Lamers & Carmichael, 1999], coeval borderland uplift events (rift pulses) [Ebdon et al, 1995;Goodwin et al, 2009;Mudge, 2015] and rifting and extension accompanied by volcanism [Mudge, 2015;Ólavsdóttir et al, 2017].…”

Seismic‐stratigraphic constraints on the age of the Faroe Islands Basalt Group, Faroe–Shetland region, Northeast Atlantic Ocean

“…Whereas the sub‐basins in the eastern (UK) half of the Faroe‐Shetland Basin preserve a proven upper Palaeozoic–Cenozoic sedimentary fill (Stoker et al, ; Stoker & Varming, ), the known record of sedimentation in the western (Faroese) half of the basin is, to date, mostly limited to the Cenozoic succession (Eocene and younger) that overlies the FIBG (Andersen, Nielsen, Sørensen, Boldreel, & Kuijpers, ; Andersen, Sørensen, Boldreel, & Nielsen, ; Ólavsdóttir, Andersen, & Boldreel, ; Ólavsdóttir, Boldreel, & Andersen, ; Ólavsdóttir et al, ; Sørensen, ; Waagstein & Heilmann‐Clausen, ). At the eastern, distal edge of the FIBG, the volcanic succession is observed on seismic‐reflection profiles to interdigitate with sedimentary rocks originating from the eastern side of the Faroe‐Shetland Basin (Helland‐Hansen, ) though the conflicting ages described above for the FIBG have thus far precluded the establishment of a robust correlation between the lower Palaeogene volcanic and sedimentary rocks across the basin.…”

“…The base of the basalt lava pile can also be mapped on seismic‐reflection profiles locally in the Faroese sector of the Faroe‐Shetland Basin (Ellefsen, Boldreel, & Larsen, ) and is observed in the Lopra‐1 well that terminated in hyaloclastic rocks of the Lopra Formation (Boldreel, ; Christie, Gollifer, & Cowper, ). Although refraction‐seismic interpretations suggest that sedimentary rocks might be present below the FIBG in the western part of the Faroe‐Shetland Basin and beneath the Faroe Platform, including Lower Paleocene rocks (Kiørboe & Petersen, ; Ólavsdóttir et al, ; Pálmason, ; Raum et al, ; Richardson, Smallwood, White, Snyder, & Maguire, ; Richardson, White, England, & Fruehn, ; Smallwood & Maresh, ; Smallwood & White, ; White et al, ), their correlation with the rock record in the eastern part of the Faroe–Shetland Basin remains ambiguous.…”

“…Whereas most of the basalts were erupted subaerially -and remain exposed on the Faroe Islands -the bulk of the succession is presently submerged, albeit remaining at or close to seabed on the Faroe Platform and the banks to the south (e.g. Wyville Thomson Ridge, Faroe Bank High) (Ólavsdóttir, Eidesgaard, & Stoker, 2017;Passey & Hitchen, 2011;Waagstein, 1988) (Figure 1). Other indicators of igneous activity include intrusive magmatism associated with the Faroe-Shetland Sill Complex (see Passey & Hitchen, 2011) and tuffaceous beds (Mudge, 2015;Watson et al, 2017).…”