Volcanic marker horizons in the upper part of the Maligât Formation on eastern Disko and Nuussuaq, Tertiary of West Greenland: syn- to post-volcanic basin movements

Abstract

Lavas from the Rinks Dal, Nordfjord and Niaqussat Members of the Maligat Formation overlying gneisses in eastern Nuussuaq are described together with an overlying young sequence of basalts not known from other areas. The Niaqussat Member lavas are the first recorded from Nuussuaq. On Disko lavas of the Nordfjord and Niaqussat Members have been found on the highest mountain tops bordering the Sermersuaq ice cap, and these two members are now known to have been present over the whole of Disko and eastern Nuussuaq. East of the Disko Gneiss Ridge the base of the Niaqussat Member forms a fairly smooth, gently south-easterly sloping surface that can be extrapolated to Nuussuaq. Eruption sites for the Nordfjord and Niaqussat Members are centred in western Disko, but feeder dykes east of the Disko Gneiss Ridge are indicated, especially for the Niaqussat Member in both Disko and Nuussuaq. There is evidence from several levels within the volcanic pile of relative subsidence in the south-east and uplift in the north-west, and these movements must have taken place in an extended period both during and after the volcanic activity.