The volcanic and sedimentary evolution of the Faeroe plateau lava group, Faeroe Islands and Faeroe-Shetland Basin, NE Atlantic
Geochemical analysis of the volcanic interval in Well 214/4-1, Faeroe-Shetland Basin, has enabled a correlation to the Lower Basalt Formation of the Faeroe Islands, ca. 240 km to the W. The volcanic interval consists of a ca. 450 m thick sequence of hyaloclastites, which are overlain by a ca. 50 m thick subaerial lava sequence. This volcanic interval is interpreted to have formed at a palaeoshoreline environment, where subaerial lavas flowed from the land surface into a substantial body of water at least 450 m deep (i.e. the Faeroe-Shetland Basin at that time), resulting in the quenching and fragmentation of magma to product the hyaloclastities. Well 214/4-1 is <50 km to the SE of the Faeroe-Shetland Escarpment, which has previously been interpreted as a hyaloclastite delta, thus implying that there a number of unrecognised hyaloclastite units within the Faeroe-Shetland Basin and that the coastline was steadily encroaching W/NW, towards the Faeroe Islands during the volcanic interval. The overlying ca. 10 m thick Coal-bearing Formation (CBF) represents a significant hiatus in the volcanic activity at the end of LBF times. Erosion and subsidence of the lava field led to the development of an expansive lacustrine environment, which resulted in the accumulation of plant material and associated detritus and chemical sediments, mainly ironstones, and the formation of mineable coal seams. Petrographic and geochemical analysis of siderite spherules within the ironstone beds from two localities on Suðuroy have helped to define margin- and centre of-lake environments, at least 10 km apart. Contemporaneous fluviatile lithologies in West Suðuroy are composed of reworked palagonitised tephra, basalt lava clasts and plant material.