The Cambrian and Ordovician rocks make up the Meguma Group, which includes sandstones, siltstones, slates, and conglomerates. In the past, gold was produced from Meguma rocks. This group of rocks underlies most of Yarmouth County. Ordovician and Silurian rocks form the White Rock Formation, which includes sandstones, siltstones, shales, conglomerates, and the volcanic rock seen at Cape Forchu. Devonian granites occur in northeastern Yarmouth County and have been mined for their tin, zinc, and copper.
The rocks seen at Cape Forchu are the volcanic rocks of the White Rock Formation. These are composed of water-lain volcanic tuff with scattered volcanic bombs, thick lava flows, volcanic ash flows, and volcanic conglomerates. In several areas, these ancient rocks are interbedded with marine sediments. This has lead geologists to believe that these rocks record the evolution of volcanic islands through prehistoric submarine volcanic eruptions.
The absence of fossils indicates these rocks formed in a cold and hostile marine environment. The rocks that now form Cape Forchu formed off the coast of what is presently North Africa and joined the fossil-rich rocks of northern Nova Scotia through the processes of continental drift. It is interesting to note that the classic examples seen from the observation area were already 200,000,000 years old when the earliest dinosaurs began roaming our planet.
