Crustal structure at the SE Greenland margin from wide-angle and normal incidence seismic data

Results from a seismic retraction and reflection line along the southeast coast of Greenland give information on both the Precambrian structures on the Greenland continent and on the effects of the Tertiary breakup of the North Atlantic. Three seismic stations on the Greenland coast recorded the airgun shots from a 279-km reflection seismic line approximately 20 km offshore. The maximum offset recorded was 313 km. The wide-angle data show crustal thickness variation from 39 km in the south to 49 km in the north, with an 8- to 17-km-thick, high-velocity (7.5 km/s) layer at the base of the crust, interpreted as underplating related to the opening of the North Atlantic in the Tertiary. The boundary between the early Proterozoic Ketilidian orogen in the south and the Archaean block to the north show little variation in seismic velocities, and the reflection pattern suggests that the Archaean underlies the Ketilidian at depth. We see no evidence that the Julianehåb Batholith at the boundary between rocks of the Ketilidian orogen and the North Atlantic block is a deep structure.