Discover Canada and Explore the Fossils and Geodiversity of Hornby Island in British Columbia
- Wayne Munday
- 2 days ago
- 5 min read
Sip back and discover Canada and explore the fossils and geodiversity of Hornby Island, a small Gulf Island off eastern Vancouver Island in British Columbia. Covering roughly 30 km², the island lies within the traditional territory of the K’ómoks First Nation and features dramatic sandstone cliffs, white sandy beaches at Tribune Bay, and forested trails around Mount Geoffrey, which rises to 330 metres with panoramic views of the Strait of Georgia and distant Coast Mountains. Its rugged shores expose the Late Cretaceous Nanaimo Group, sedimentary rocks deposited between 92 and 65 million years ago in a marine forearc basin formed between the Wrangellia terrane and the North American continent. Over millions of years, tectonic uplift, Cordilleran mountain building, Pleistocene glacial sculpting and weathering has shaped the island’s dramatic sandstone cliffs, headlands and fossil beaches, including the striking honeycomb (tafoni) sandstone formations at Helliwell Provincial Park and Sandpiper Beach. Fossiliferous exposures, particularly in the Northumberland Formation at Boulder Point and Collishaw Point, reveal a diverse Late Cretaceous marine ecosystem. Fossils include ammonites such as Pachydiscus and Nostoceras, baculites, bivalves, gastropods, shark teeth and rare vertebrates like the marine diving bird Maaqwi cascadensis and fragmentary bones of a azhdarchoid pterosaur. Visitors are encouraged to respect park regulations and engage with the Hornby Island Natural History Centre and Vancouver Island Paleontological Society to support local fossil stewardship and education.
Hornby Island is a small and picturesque island located off the eastern coast of Vancouver Island in the heart of the Salish Sea roughly 80 Km northwest of Nanaimo and about 200 Km north of Victoria. Hornby Island is within the sacred waters, forests and shores of the K’ómoks First Nation whose history begins with the arrival of their ancestors to this territory at the end of the last Ice Age. The island is part of the Northern Gulf Islands archipelago known for its mild climate, scenic coastal trails and mix of forests, cliffs and marine wildlife of Bald Eagles, Harbour Seals, Sea Lions and migrating Orcas during late spring, summer, and autumn when the Chinook, Coho and Sockeye salmon run.
Hornby Island is compact at about 30 km² where the southern coast features dramatic sandstone headlands and sea cliffs sculpted by waves, especially around Helliwell Provincial Park, where hiking trails navigate through Douglas Fir forests and open coastal bluffs with sweeping ocean views. To the north and west, Tribune Bay Provincial Park known as “Little Hawaii” because of its the white sandy beaches aquamarine sea. Inland, Mount Geoffrey rises to about 330 metres, providing panoramic views of the Strait of Georgia, the Comox Valley, and the distant snow-capped Coast Mountains. To reach Hornby Island visitors typically travel by road and BCFerry from Vancouver Island, a short ferry ride from Buckley Bay takes you first to Denman Island, followed by a second brief ferry crossing from Gravelly Bay (Denman Island) to Shingle Spit (Hornby Island).
Although Hornby Island is relatively small its rocky shores expose the Late Cretaceous Nanaimo Group of sedimentary rocks deposited between 92 and 65 million years ago in a forearc basin that formed between the Wrangellia terrane and the North American continent.
The Wrangellia terrane defines part of the underlying geology of the basins that are formed along the Pacific margin of North America. This is a vast allochthonous crustal fragment that means it was formed elsewhere and has been pushed tectonically on top of another crustal block to its current position. More specifically, the Wrangellia terrane is a massive oceanic plateau formed near to the equator by most likely the mantle plum from the Galápagos hotspot and is composed mainly of thick Triassic Period flood basalts. Over time Wrangellia drifted northward colliding or accreting with the western margin of North America during the Mesozoic Era.
One of the standout geodiversity features of Hornby Island is the honeycomb shaped sandstone formations exposed on the foreshore and cliffs at low tide in Helliwell Provincial Park and at Sandpiper Beach. The sandstone is shaped by the process of tafoni weathering where salt from ocean spray, rain, waves or from algae infiltrates the porous Nanaimo Group sandstone, crystallises and gradually expands eroding the the rock to form pitted surfaces.
Over 27 million years between the Turonian and Maastrichtian Stages the Nanaimo Group was deposited. This marine group is dominated by interbedded coarse-grained sandstone and conglomerate alongside finer siltstone and fossiliferous mudstones making up the Northumberland, Gabriola, Spray and De Courcy formations. Hornby Island is located in the Georgia Basin system of a much larger marine sedimentary forearc basin that occupied the intervening subduction zone between the uplifted Wrangellia terrane and the continental margin of the North American tectonic plate. Over time the Nanaimo Group was uplifted and deformed by Cordilleran mountain building, sculpted by the advance and retreat of the Pleistocene Cordilleran Ice Sheet and exposed to the weather and elements of coastal erosion to shape today's cliffs, headlands and fossil beaches.
Within the Nanaimo Group and exposed on Hornby Island at Boulder Point, also known as Fossil Beach, and Collishaw Point is the fossiliferous Northumberland Formation laid down during the Campanian Stage and possibly into the Maastrichtian between 80 - 66 million years ago. The fossiliferous Northumberland Formation yields a diverse marine fossil assemblage preserved in hard, rounded concretions that fall from the cliffs.
The concretions hold several species of heteromorph ammonites often preserved in death assemblages and includes the families Baculitidae, Diplomoceratidae and Nostoceratidae and the species of Baculites occidentalis, Diplomoceras cylindraceum, Nostoceras hornbyense, Exiteloceras densicostatum and Solenoceras exornatus. Bivalves and gastropods are also abundant and are often found as molds or nacreous mother-of-pearl shells.
Although vertebrate fossils in the Northumberland Formation are relatively rare, they do include dense concentrations of teeth from lamniform ('fish of prey') commonly known as Mackerel Sharks and squaliform "Dog Fish" sharks. There is also evidence of diving birds such as Maaqwi cascadensis a marine diving bird adapted for underwater hunting of fish and small aquatic prey as well as fragmentary fossil bones of a humerus, dorsal vertebrae and other fragments from the first pterosaur from the Northumberland Formation identified as an azhdarchoid.
One notable case of misidentification of a fossil on Hornby Island involves Gwawinapterus beardi. Originally described from a fragmentary toothed jaw as an istiodactylid pterosaur. Subsequent research has shown that the jaw actually belongs to a predatory saurodontid fish with the initial error arising from the physical similarity between the teeth of istiodactylid pterosaurs and saurodontids. This revision clarifies that Gwawinapterus beardi was a marine predatory fish rather than a flying reptile.
Visitors are encouraged to follow park regulations and reporting protocols to Hornby Island Natural History Centre and Vancouver Island Paleontological Society to help protect the local stewardship and public education of an ancient ocean ecosystem.