The Avalon terrane exposed here is termed an exotic terrane because it formed elsewhere and was thrust onto the continental edge.  The rocks along the coast here were once formed in an island arc and collided with North America during the Acadian orogeny during Silurian times.  The rocks were folded and metamorphosed as the orogenic processes unfolded.  Here near the lighthouse is a fault which juxtaposes light and dark metamorphic rock.