 Recent (1990–2000) geological studies and rock age dating by geologists from Oxford Brookes University shows that the gneisses probably formed around 620–600 million years ago during the Late Pre-Cambrian Age Cadomian Orogeny.The quartz diorite sheets were intruded during this Cadomian deformation and metamorphic event.All the Sark rocks (and those of the nearby Channel Islands of Guernsey and Alderney) formed during geological activity in the continental crust above an ancient subduction zone.