Outcrops of Proterozoic rocks consist of a complex suite of comagmatic intrusives which exhibit a variable degree of deformation and are correlated with the Early Proterozoic Lincoln Complex. On southern Saint Peter Island, felsic volcanics, considered to be equivalent to the 1630 Ma rhyolites on Saint Francis Island are intruded by diorite. Outcrops on Goat Island consist of granites to adamellites of the Middle Proterozoic Hiltaba suite. A detailed correlation has been made between these basement exposures and those along the mainland coast.