Lithostratigraphy, geology and geochemistry of the Tertiary volcanic rocks on Svartenhuk Halvø and adjoining areas, West Greenland

• Published in: GEUS Bulletin
• Main Authors: Larsen, Jørgen Gutzon, Larsen, Lotte Melchior
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geological Survey of Denmark and Greenland (GEUS) 2022
• Subjects: Palaeogene; Flood basalts; Vaigat Formation; Svartenhuk Formation; Naqerloq Formation; geology; Nunavik; Greenland; Nuussuaq; Vaigat; Svartenhuk; Innerit; Nerutusoq; Skalø; Svartenhuk halvø
• Online Access: https://geusbulletin.org/index.php/geusb/article/view/8295; https://doi.org/10.34194/geusb.v50.8295

The Palaeogene volcanic succession in the northern part of the Nuussuaq Basin in West Greenland comprises three formations: the Vaigat and Svartenhuk Formations of Paleocene age (61–58 Ma) and the Naqerloq Formation of Eocene age (57–54 Ma). In this study, we formalise and describe the volcanic stratigraphy on Svartenhuk Halvø and the areas with lavas that flowed across the basin boundary onto the adjoining basement areas in the north and east. The Vaigat Formation comprises three members. The Kakilisaat and Nerutusoq Members are of minor volume and consist of, respectively, crustally contaminated basalts and chemically enriched basalts with relatively high contents of incompatible trace elements. They are overlain by the voluminous Nunavik Member of tholeiitic picrites (MgO ≥12 wt%) and subordinate magnesian basalts. The oldest volcanic deposits are commonly foreset-bedded hyaloclastites, and the overlying subaerial lavas are mainly thin, grey, crumbling flows. Eruption sites were mainly within the basin, with depocentres in the south and hyaloclastite and lava transport directions towards the north. Thicknesses vary from up to at least 2000 m in the south to ≥380 m in the northernmost exposures close to 72°N. The Svartenhuk Formation comprises four members. The lowest, Kuugaartorfik Member, is up to 100 m thick and consists partly of quartzofeldspathic and partly volcanogenic sediments; it is restricted to northern Svartenhuk Halvø and the Innerit peninsula. The overlying volcanic Tunuarsuk, Nuuit and Skalø Members are voluminous and widespread, with a combined thickness of up to 1800 m. They consist of tholeiitic basalts with similar chemical compositions but with correlatable stratigraphic variation patterns. The Tunuarsuk Member consists of interspersed flow groups of thin, grey flows and massive, brown flows; the Nuuit Member comprises mainly massive brown flows, and the Skalø Member is dominated by light grey flows. The Svartenhuk Formation oversteps the Vaigat Formation on the basement in the north and ...