Lithostratigraphy of the early Tertiary volcanic rocks of central West Greenland

Abstract

A sequence of flood basalts, in places more than 8-10 km thick, was erupted during the Early Tertiary in the central part of West Greenland between latitudes 69° and 73°N. The volcanic rocks rest on Precambrian metamorphic rocks and non-marine and marine sediments from the Cretaceous and Paleocene. The lower part of the volcanic sequence is dominated by tholeiitic olivinerich basalts and picrite basalts, whereas the upper part is characterized by tholeiitic basalts with plagioclase as the dominant phenocryst mineral; transitional and alkaline lavas and tuffs are found, especially in the upper part of the sequence. The geology of the Tertiary igneous rocks has been summarized by Munck & Noe-Nygaard (1957), Rosenkrantz & Pulvertaft (1969) and Clarke & Pedersen (in press). However, until now no formal lithostratigraphy has been established. A geological map at scale 1:100 000 covering the greater part of Nugssuaq (sheet Agatdal-70 V. 1 Nord) has been published by GGU.