Rock of Grenville Age from Rockall Bank

Abstract

WE report an age of 987 ± 5 m.y. obtained on a sample drilled from an outcrop at the southern end of Rockall Bank. The specimen was part of a 7-cm long core of andesine-orthopyroxene-biotite-quartz granulite and its petrography has been described by Roberts, Ardus and Dearnley1. Surveillance by underwater television of the outcrop prior to drilling left very little doubt that it is in place and is not an enormous erratic block.