Lithostratigraphy of the Tertiary Vaigat Formation on Disko, central West Greenland

Abstract

The lithostratigraphy of the early Tertiary Vaigat Formation on Disko is presented. The formation is divided into six members: Naujanguit Member, Asuk Member, Kûgánguaq Member, Qordlortorssuaq Member, Ordlingassoq Member and Manítdlat Member. The members were formed by two major igneous events. The first event gave rise to the vo!canic rocks from the Naujånguit Member and two minor vo!canic systems enclosed therein: the Asuk and Kiigånguaq Members. The basalts of the Qordlortorssuaq Member constitute the waning phase of the first igneous event. The second igneous event gave rise to the vo!canic rocks of the Ordlingassoq Member within which are enclosed the alkaline basalts of the Manitdlat Member. The members are composed of the folIowing igneous rocks: Naujanguit Member: tholeiitic picrites, minor silicic basalts and olivine-poor tholeiitic basalts; Asuk Member: silicic basalts and magnesian andesites, many rocks carry native iron; Kfigånguaq Member: silicic basalts and magnesian andesites; Qordlortorssuaq Member: olivine-poor tholeiitic basalts; Ordlingassoq Member: tholeiitic picrites, minor alkaline picrites; Manitdlat Member: alkaline picrites and alkaline basalts.