Mapping of the Isukasia sheet, southern West Greenland

Abstract

Field work for the Isukasia map sheet north of Godthåbsfjord, started in 1981 (Allaart et al., 1982), was continued in 1982. A tent base camp was set up at the fjord Kangiussaq both summers. In 1982 seventeen fjeld teams and the glaciological station Qamanârssup sermia were supplied from the base by the GGU cutter J. F. Johnstrup and by a Jet Ranger helicopter based in Kangiussaq. Twelve mapping geologists worked on the two map sheets Ivisartoq and Isukasia, and five teams carried out ore geological, geochemical and geophysical investigations (see Appel, Chadwick et al., Jensen & Secher, and Secher, this volume). The field work was carried out from June 20th to August 28th. The Isukasia map sheet is situated north-east of the head of Fiskefjord, around the lake Taserssuaq. To the east it is bounded by the Inland lee, from which the glacier Sarqap sermia enters Taserssuaq. Most of the area is a lake strewn, undulating plateau at elevations between 500 and 800 m. Outcrops are generally good aIthough there are some Quaternary boulder fields, the largest of whieh extends over some 25 km2 in the north-east corner of the map sheet. The north-north-east trending Ataneq fauIt zone (see below), which oeeurs some 25 km east of Taserssuaq, separates an area of early Archaean rocks (induding the Isua supracrustals) from rocks to its west of probable late Archaean age. The younger rocks make up the bulk of the Isukasia map sheet.