Friday, 23 October 2020

HORNBY ISLAND FOSSILS

Pachydiscus suchiaensis ID: 18-08-CP-002
The beautiful ammonite you see here nestled amongst the seaweed and modern oysters clinging to the grey shales of the Northumberland Formation is the Upper Cretaceous (Campanian) ammonite Pachydiscus suchiaensis. This is one of my favourite species and is treasured both for its beauty and the fossil site it hails from. 

This darling was found in situ in the 72 million-year-old sediments at Collishaw Point on the northwest side of Hornby Island, southwestern British Columbia.

Hornby is a glorious place to collect. The island is beautiful in its own right and the fossils from here often keep some of their original shell or nacre which makes them quite fetching. This fellow is found amongst gastropods, shark teeth, fossil crabs, baculites and other bivalve fossils. 

Many of the fossils found at this locality are found in concretions rolled smooth by time and tide. The concretions you find on the beach are generally round or oval in shape and are made up of hard, compacted sedimentary rock. 

If you are lucky, when you split them you see a fossil hidden within. That is not always the case but the rewards are worth the effort. These past few years, many new and wonderful specimens have been unearthed — particularly by members of the Vancouver Island Palaeontological Society. 

Two particular finds are jaw-droppers — a Diploceras longer than your arm and Actinosepia, gladius — internal hard body part found in many cephalopods — of a Vampyropod, a member of the proposed group Vampyropoda — equivalent to the superorder Octopodiformes — which includes vampire squid and octopus. Not all of these beauties come out in one piece and as well as amazing collecting skill, the VIPS boasts some of the best Fossil Preparators in British Columbia. A nod of respect to both Jason Hawley and Rick Ross in this regard. Rick is a skilled collector and found a rather nice and rare pachydiscid ammonite at Hornby this past year that I had never seen before. It has been a good year for collecting at Collishaw Point. Another notable find was the decapod, Archaeopus vancouverensis (Woodward 1896), found by Adam Melzak this past summer.

The Courtenay Museum, Qualicum Museum and Pacific Museum of the Earth have delightful collections of specimens from the Upper Cretaceous of Hornby Island. This lovely heteromorph ammonite, Nostoceras hornbyense (Whiteaves, 1895) is a classic. The photo below is courtesy of John Fam, Vice-Chair of the Vancouver Paleontological Society (VIPS) on a recent visit to poke through the collections at the Pacific Museum of the Earth. 

It is a classic example of the heteromorph specimens found at Hornby. Bob Copeman found the best Nostoceras hornbyense I have ever seen from these outcrops. Lucky for you, a replica of that specimen has been made is available to be purchased from the VIPS. Always a nice addition to the collection — especially if you keep a teaching collection where specimens need to be handled by younger, rougher hands.

Nostoceras hornbyense (Whiteaves, 1895)
The main topographic feature on Hornby Island is an arcuate mountain consisting of the resistant cliff-forming Geoffrey formation. Near Shingle Spit about half a mile from the coast is Mt. Geoffrey 920-foot peak; from there the mountain gradually drops in elevation to the southeast and to the north.  

It consists of a structurally simple 700-foot conglomerate homocline striking N 20° W and dipping to the northeast at a shallow angle of about 6°. 

The apex of the arcuate mountain belt points to the southwest. The coast of Hornby is probably a rising shoreline, as indicated by the almost perpendicular cliffs along its periphery. A hundred (100) foot cliffs of Lambert shale extends from Shingle Spit to Phipps Point, while from the latter to Boulder Point, the cliffs are not as steep and are covered in many places by vegetation.

Behind the mountain and almost enclosed by it is the fertile, green Strachan Valley. On the large peninsula which extends in a southeast direction from the north of the island towards St. John’s Point, the Hornby Formation outcrops forming the cliffs on the east side of Tribune Bay. The highest of these is about 200 feet. The argillaceous Lambert and Spray formations form the subdued lowlands of the island.