Some Radiometric Rock Ages and the Problem of the Southward Continuation of the East Greenland Caledonian Orogeny

THE work of Lauge Koch and others has established that a powerful Caledonian orogeny occurred in what is now the coastal region of East Greenland, north of Scoresby Sound. Whether this orogenic belt continues down the east coast of Greenland and joins the Caledonian mountain belt of eastern North America has been an open question but can now be answered by means of radiometric age determinations. The metamorphic basement rocks between Kangerdlugssuaq and Angmagssalik, which have a dominantly east–west structure1, do not seem to fit into the idea of their having been involved in a north–south Caledonian orogenic belt; but if the effects of a Caledonian orogeny did not obliterate the earlier structures, this hypothesis would have to be accepted as a possibility.