Monday 22 July 2019

AMMONITES FROM THE MYSTERIOUS CREEK FORMATION

Cadoceras tonniense, Mysterious Creek Formation
The Cretaceous-Jurassic exposures near Harrison Lake, British Columbia are an easy two hour drive from Vancouver and another hour or so to our final destination, the unyielding siltstone of the Callovian, 166 million-year-old, Mysterious Creek Formation.

A few hours of collecting yield multiple bivalves, ammonites, including what looks to be two new species. Amongst the best specimens of the day are several small, fairly well preserved Cadoceras (Paracadoceras) tonniense, a few Cadoceras (Pseudocadoceras) grewingki and two relatively complete specimens of the larger, smooth Cadoceras comma.

Interestingly, the ammonites from here are quite similar to the ones found within the lower part of the Chinitna Formation, Alaska and Jurassic Point, Kyuquot, on the west coast of Vancouver Island. Further up the road, we photograph blocks of buchia and large boulders encrusted with perfectly preserved belemnites from ancient squid. The siltstones at Harrison have also offered up a small section of vertebra from a poorly preserved marine reptile. I'm ever hopeful to find the rest of that big fellow.

There are many fossils to be found on the west side of the Harrison lake near the town of Harrison, British Columbia. Exploration of the geology around Harrison Lake has a long history with geologists from the Geological Survey of Canada studying geology and paleontological exposures as far back as the 1880s. They were probably looking for coal exposures —  but happy day, they found fossils!

The paleo outcrops were first mentioned in the Geological Survey of Canada's Director's Report in 1888 (Selwyn, 1888), then studied by Whiteaves a year later. Whiteaves identified the prolific bivalve Aucella (now Buchia) from several specimens collected in 1882 by A. Bowman of the Geological Survey of Canada. The first detailed geological work in the Harrison Lake area was undertaken in a doctoral study by Crickmay (1925), who compiled a geological map, describing the stratigraphy and establishing the formational names, many of which we still use today. Crickmay went on to interpret the paleogeography and structure of the region.