It is impossible to overstate the importance of the Burgess Shale fossil beds to geology, and every amateur, professional, and expert geologist in BC should visit a quarry at least once. The main Burgess Shale quarries are situated in Yoho National Park near Field, BC, and a stop at the interpretive centre in Field is an absolute must. A tour of the site is also highly recommended and can be booked here. Why visit? Because the Burgess Shale remains one of the most important records of early life on our planet, and is one of the rare locations where soft-bodied animals (like worms and slugs) are preserved in the rock record. The information gleaned from the Burgess Shale revolutionized our understanding of the explosion of complex life on Earth over 500 million years ago, and new discoveries are still being made!
History of the Burgess Shale
The original Burgess Shale quarry was discovered almost by accident in 1909 by Charles Doolittle Walcott from the Smithsonian Institute in Washington, USA (1). Walcott ran expeditions to the quarry every year from 1910 to 1924, gathering over 65,000 specimens that he shipped back to the Smithsonian (2). It was not until the 1960s that the Burgess Shale gained notoriety as other scientists re-examined Walcott's fossils and recognized their importance. The Burgess Shale became a UNESCO World Heritage Site in 1980 (3), and then part of the UNESCO Canadian Rocky Mountain Parks World Heritage Site in 1984. Presently, the Royal Ontario Museum manages fossil collections form the various Burgess Shale quarries, and they have done an excellent job making the fossil collections "available" to the public (4). Their 3D reconstructions and animations of different fossils are really cool, and are definitely worth spending some time watching! Here is one of their many videos:
Why so important?
Over half of the animal phyla that define life on Earth do not have hard parts and so we know very little about their geological history. Sites like the Burgess Shale change that because they give us a window to look back through time. The Burgess Shale shows us that 506 million years ago, life thrived in the world's oceans, and that nearly all phyla were present (5, 6). Phyla (or multiple phylums) are broad groups of animals within kingdoms (for example, people belong to Phylum Chordata in Kingdom Animalia). In the Burgess Shale there are early members of Phylums Porifera (sponges), Cnidaria (corals and jelly fish), Brachiopoda (brachiopods), Mollusca (clams), Arthropoda (crabs and insects), Echinodermata (echinoids and sea cucumbers), Priapulida (acorn worms), Annelida (earthworms), and Chordata (animals with a spinal cord). Members of Porifera, Priapulida, Annelida, and Chordata are soft-bodied.
Geology of the Burgess Shale
The Burgess Shale preserves so many cool fossils because of its geological setting. In the Middlle Cambrian (over 500 million years ago), the western margin of North America was close to the Alberta-BC border, and BC was part of the ocean. North America was close to the equator and a large, shallow-water carbonate platform (similar to the Bahamas today) covered large parts of Alberta and a bit of BC (4). The edge of the platform was the Cathedral Escarpment, which is a 200 m high cliff. The Burgess Shale sites are situated at the base of the cliff. Every so often, the edge of the Cathedral Escarpment would collapse and form turbidity currents that transported a lot of mud into deeper water through a series of canyons (see Goodspeed Fossil Beds post for info on turbidites). The mud in these currents would rapidly bury animals living on the seafloor below the cliff. The fine-grained nature of the mud prevented decomposition of the buried animals and resulted in their exceptional preservation (4, 7). There have been a number of discoveries of Burgess Shale-type fossil communities along the Cathedral Escarpment and new discoveries are being made all the time (5, 6). Who know what else we will learn about early life from these incredible fossil beds!
Please note that fossil collecting in not allowed at any Burgess Shale site as all are within the NESCO Canadian Rocky Mountain Parks World Heritage Site. It is not only illegal, but also comes with a heavy fine and possible jail time. Best just to enjoy this provincial and national treasure!
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Info Sources:
1) Morris, S. C., and Whittington, H. B., 1979, The animals of the Burgess Shale: Scientific American, v. 241, p. 122-133.
5) Nanglu, K., Caron, J.-B. & Gaines, R.R. (2020). The Burgess Shale Paleocommunity with New Insights from Marble Canyon, British Columbia. Paleobiology, 46, 58-81.
6) Caron, J.B., Gaines, R.R., Aria, C., Mangano, M.G. & Streng, M. (2014). A New Phyllopod Bed-Like Assemblage from the Burgess Shale of the Canadian Rockies. Nat Commun, 5, 3210.
7) Morris, S.C. & Whittington, H.B. (1979). The Animals of the Burgess Shale. Scientific American, 241, 122-133.
Very cool