The only significant outcropsof intrusive igneous rocks in the Torbay district are between Black Head and Anstey's Cove, where microgabbros (‘dolerite') are intruded into the Upper Devonian Saltern Cove Formation. The intrusions are associated with basic tuffs and believed to be typical of alkaline or sub-alkaline basalts of a within-plate Ocean Island type, as elsewhere in Devon and Cornwall.