A geophysical investigation of the south-east Greenland continental margin

Abstract

During the summers of 1973 and 1974 geophysical observations were made, aboard R.R.S. Shackleton, across the south east Greenland continental margin, between 58 and 65 N. The thesis describes the reduction and interpretation of the magnetic, bathymetric, gravimetric, and deep seismic reflection data and gives details of the digital deconvolution and C.D.P. stacking techniques developed for processing the reflection data. The magnetic results indicate that, south of 63 N., anomaly 24 is the earliest recognisable oceanic magnetic anomaly. North of 63 N., anomalies 22-24 cut out against the margin, and a complementary widening of ocean floor of this age, on the opposite Rockall margin, north of Hatton Bank, indicates that a local westward migration of the spreading axis occurred, north of 63 N., shortly after the split. Igneous intrusives, outcropping on the rise, post-date the continental split by several million years, indicating that the volcanic activity of East Greenland may have occurred some time after continental separation started. Airgun and sparker profiles show three major sediment groups. Two groups of Tertiary age are separated by an erosional unconformity, beneath the rise north of 62 N. The upper sediments are interpreted as contour current deposits of Miocene and later age, and the lower sediments as lithified oozes of about Eocene age. Below these Tertiary sediments, older, seaward dipping reflectors occur between anomaly 24 and the scarp. These are interpreted as Mesozoic sediments overlying subsided continental crust. The oceanic-continental crustal boundary, as recognised from magnetic anomalies, occurs to the east of this subsided region and lies up to 80 km seaward of the scarp, which is an erosional feature cut by contour currents. Gravity profiles indicate that the main change in crustal thickness beneath the margin lies up to 80 km landward of the scarp north of 63.5 N; but corresponds more nearly with the scarp further south.