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NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Skaarup, N. (2002). Evidence for continental crust in the offshore Palaeogene volcanic province, central West Greenland. Geology of Greenland Survey Bulletin, 191, 97-102. https://doi.org/10.34194/ggub.v191.5135 _______________ The Palaeogene volcanic province of central West Greenland extends for 550 km from north to south and 200 km from east to west (Henderson 1973; Henderson et al. 1981; Whittaker 1996). In a preliminary interpretation of the area offshore Disko and Nuussuaq, based on older seismic data, Whittaker (1996) described a number of large rotated fault blocks containing structural closures at top volcanic level that could indicate leads capable of trapping hydrocarbons. This work, combined with the discovery of oil in the basalts onshore, led the Geological Survey of Denmark and Greenland (GEUS) to acquire 1960 km of multi-channel 2D seismic data in the area between 68°N and 71°N in 1995 (Fig. 1). These seismic data are the primary data source for the interpretation presented in this paper.

The coastal structure in central West Greenland is expressed by Palaeogene basalts which show pronounced seaward dip. Traced along strike the tilted basalts occur in two segments, separated by an area in which dips are low. Within these segments the lavas have been displaced by extensional faults with strike parallel to the strike of the lavas and dip and downthrow to the landward side. This structural pattern bears many similarities to regional structural features in volcanic rifted margins in other parts of the world, although in West Greenland the continent-ocean boundary is situated more than 100 km west of the coast. The structure has previously been studied onshore and has now been studied in high-resolution seismic data acquired both west of the coast and in the sounds between the Nuussuaq and Svartenhuk peninsulas. From the offshore data it can be seen that within the sections correlated with mid-Paleocene volcanic rocks onshore, the tilting of the lavas took place almost entirely after eruption, as there is little or no indication of any increase of dip towards the faults or of fan-shaped geometry in cross-section. However, southwest of Ubekendt Ejland and stratigraphically within Early Eocene lavas, dips can be seen to increase with depth in several fault blocks, indicating that tilting was active during eruption of these lavas. It is therefore concluded that tilting of the volcanic rocks in the coastal zone took place largely in the Eocene. This conclusion is corroborated by the following onshore evidence: Firstly, the angle of discordance between seaward-dipping Eocene lavas and the underlying tilted Paleocene lavas is small, where observed at all, so the mid-Paleocene lavas must owe their seaward dip largely to tilting during the Eocene. Secondly, Early Eocene ages have been obtained from sequentially tilted dykes onshore. This tilting and concomitant extensional faulting was contemporaneous with the second phase of seafloor spreading in the Labrador Sea which took place during the Eocene. The first phase of seafloor spreading in this sea took place between magnetochrons 27r and 24r and was not accompanied by significant rifting of lavas in central West Greenland. It can also be seen from the seismic data that the tilted lavas level out less than 25 km from the coast. West of this, the volcanics generally show very low dips and thin gradually towards the continent-ocean boundary.

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NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Christiansen, F. G., Boesen, A., Bojesen-Koefoed, J. A., Chalmers, J. A., Dalhoff, F., Dam, G., Ferré Hjortkjær, B., Kristensen, L., Melchior Larsen, L., Marcussen, C., Mathiesen, A., Nøhr-Hansen, H., Pedersen, A. K., Pedersen, G. K., Pulvertaft, T. C. R., Skaarup, N., & Sønderholm, M. (1999). Petroleum geological activities in West Greenland in 1998. Geology of Greenland Survey Bulletin, 183, 46-56. https://doi.org/10.34194/ggub.v183.5204 _______________ In the last few years there has been renewed interest for petroleum exploration in West Greenland and licences have been granted to two groups of companies: the Fylla licence operated by Statoil was awarded late in 1996; the Sisimiut-West licence operated by Phillips Petroleum was awarded in the summer of 1998 (Fig. 1). The first offshore well for more than 20 years will be drilled in the year 2000 on one of the very spectacular structures within the Fylla area. To stimulate further petroleum exploration around Greenland – and in particular in West Greenland – a new licensing policy has been adopted. In July 1998, the administration of mineral and petroleum resources was transferred from the Danish Ministry of Environment and Energy to the Bureau of Minerals and Petroleum under the Government of Greenland in Nuuk. Shortly after this, the Greenlandic and Danish governments decided to develop a new exploration strategy. A working group consisting of members from the authorities (including the Geological Survey of Denmark and Greenland – GEUS) made recommendations on the best ways to stimulate exploration in the various regions on- and offshore Greenland. The strategy work included discussions with seismic companies because it was considered important that industry acquires additional seismic data in the seasons 1999 and 2000.