The rocks of St. Martins are Permian-Triassic age, about 250 million years old, and belong to the Honeycomb Point, Quaco and Echo Cove formations. The sea caves are in the red Honeycomb Point Formation. The coarse boulder conglomerate is part of the Quaco Formation. The contact of the two formations is easily seen at the east end of the beach in front of the restaurants. Very few fossils are found in these rocks. Poorly preserved plant fossils were found in the Echo Cove Formation many decades ago.
Bay of Fundy Rocks
The Permian-Triassic rocks seen at St. Martins dip under the Bay of Fundy and emerge on the Nova Scotia side of the bay near Parrsboro and Blomidon. Nova Scotia’s fossil history includes the oldest dinosaurs in North America found in Triassic age rocks. Rocks in Nova Scotia include fossils similar to Coelophysis. Our rocks are too old to have dinosaur fossils.
The Triassic rocks in New Brunswick represent the oldest part of the time period, and may even extend back in geologic time to the Permian Period. Permian rocks in Prince Edward Island have produced reptile fossils like Bathygnathus. Possible reptile footprints have been seen here!
Waves on the Bay of Fundy pound relentlessly on the coastal cliffs. The harbour at St. Martins has beautiful examples of sea caves, shallow features carved into sandstone and conglomerate. Sea caves are caused by physical erosion, unlike chemical solution caves in karst landscapes where carbonate bedrock has been dissolved by natural acids in rain and groundwater. In sedimentary rocks like these the caves may form along rock layers. You can see this where the boulder conglomerate meets the red sandstone. The cave floor is on the same angle as the rock layers.