Morphologies and emplacement mechanisms of the lava flows of the Faroe Islands Basalt Group, Faroe Islands, NE Atlantic Ocean

Abstract

The Palaeogene Faroe Islands Basalt Group (FIBG) comprises three eruptive sequences or formations, all emplaced into a subaerial environment during the development of the extensive continental flood basalt province that stretches from East Greenland through the Faroe Islands and into the Faroe-Shetland Basin. The Beinisvørð Formation, having a tabular-classic facies architecture, is composed of a sequence of simple flows each comprising a single sheet lobe. The Beinisvørð Formation is overlain by the distinctly contrasting Malinstindur Formation that has a compound-braided facies architecture. The Enni Formation occurs at the top of the sequence and consists of a mixture of simple and compound flows with tabular-classic and compound-braided facies architectures, respectively. Surface and internal characteristics of the sheet lobes of the Beinisvørð and Enni formations indicate emplacement through inflation, which is more obvious for the tube-fed compound flows of the Malinstindur and Enni formations. The difference between the simple and compound flow sequences of the FIBG is, most likely, linked to the manner in which the lava was supplied during the eruption and the eruptive style of the volcanic system. The sheet lobes were erupted over laterally extensive areas from fissure systems which had a continuous supply of lava, which contrasts with the tube-fed compound flows which were erupted in a gradual, piecemeal manner from pointsourced, low shield volcanoes with limited areal extents.

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

“…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. 1): (1) Enni Formation, (2) Malinstindur Formation, (3) Beinisvør› Formation and (4) Lopra Formation.…”

“…The additional formations are related to relatively thin sedimentary and volcaniclastic interbeds (Passey & Bell, 2007), which unusually occur high up in the lava sequence in the Faroe Islands (Fig. 1), whereas elsewhere, sedimentary interlayers are often restricted to the basal part of flood basalt sequences observed in many onshore examples (e.g.…”

“…The gross thickness of the volcanic succession in the Faroe Islands is thought to be 6500-7000 m, of which 3000 m are observed above sea-level (Ellis et al 2002;Passey & Bell, 2007). The onshore distribution of the formations is shown in Figure 1b.…”

“…The Enni Formation consists of a mixture of simple and compound lava flows, with a remnant thickness of 900 m with a few hundred metres removed due to erosion (Ellis et al 2002;Passey & Bell, 2007) (Figs 2e,3). 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.…”

Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

“…Pinkerton and Sparks 1978;Lipman and Banks 1987;Self et al 1997;Calvari and Pinkerton 1999;Cashman et al 1999;Kilburn 2000;Jerram 2002, Passey andBell 2007), such studies of more silicic lava flows are comparatively few (e.g. Fink 1983;de Silva et al 1994;Fujii and Nakada 1999;Uia et al 1999;Castro et al 2002;Harris et al 2002;Cioni and Funedda 2005;Tuffen et al 2013;Magnall et al 2016Magnall et al , 2017Latutrie et al 2017).…”