A revised lithostratigraphic nomenclature for the Palaeogene Faroe Islands Basalt Group, NE Atlantic Ocean

Abstract

The Palaeogene volcanic succession of the Faroe Islands in the NE Atlantic Ocean is formalised using a purely lithostratigraphic approach and following international guidelines. The Faroe Islands Basalt Group (FIBG) has a gross stratigraphic thickness of ∼6·6 km, dominated by subaerial basalt lava flows, and is subdivided into seven formations. The Lopra Formation forms the basal ∼1·1 km of the Lopra-1/1A borehole, dominated by hyaloclastites, volcaniclastic sandstones and invasive basaltic lavas/sills. It is overlain by the ∼3·25 km-thick Beinisvørð Formation, dominated by laterally extensive basalt sheet lobes separated by minor volcaniclastic lithologies. The Beinisvørð Formation is overlain by the <15 m-thick, inter-eruption, coal-bearing facies of the Prestfjall Formation and the <50 m-thick, syn-eruption, pyroclastic and sedimentary facies of the Hvannhagi Formation. Lava flow volcanic activity resumed with the <1·4 km-thick Malinstindur Formation, dominated by thinly bedded compound basalt lava flows. The top of this formation is marked by a regional disconformity surface, overlain by sandstone and conglomerate deposits of the maximum 30 m-thick Sneis Formation, a newly recognised stratigraphic unit. The final phase of volcanism recorded on the Faroe Islands consists of the >900 m-thick Enni Formation composed of a mixture of basalt sheet lobes and compound flows with abundant volcaniclastic units, e.g. the Argir Beds, that may require a further subdivision at this stratigraphic level. The new lithostratigraphy allows for more refined biostratigraphical and sequence stratigraphic correlations and prepares for a revised geological map of the Faroe Islands.