Name: Burgess Shale
Location: British Columbia
Age: Middle Cambrian (505 Ma)


The Burgess Shale is located on the eastern edge of the Canadian Rocky Mountains in what is now southeastern British Columbia in North America. It is essentially a small fossil ridge (about the size of a city block) that runs along Wapta Mountain and Mount Field in Yoho National Park. Mount Burgess, which is the namesake of the famous fossil site, is located nearby.

Two geological formations, the Cathedral Formation and the Stephen Formation, are associated with the Burgess Shale. The Burgess Shale is at the interface between these two formations, though it lies within the deeper water shale deposits of the Stephen Formation. The Burgess Shale is composed of well-laminated graded beds; this means that the deposits are arrayed in layers with a gradual decrease in the size of the particles which make up those rocks as one goes up those layers. This arrangement is indicative of episodic deposition, i.e., the sediment was deposited, layer after layer, at irregular intervals.

Figure 1. Geomorphic schematic of the Burgess Shale (Briggs et al., 1995). Note that recent research has shown that the 'thick' and 'thin' successions of the Stephen Formation are actually parts of two different formations (Fletcher and Collins, 1998).
The Cathedral Formation, on the other hand, is a shallow-water carbonate complex (essentially a reef) that forms a submarine escarpment (an underwater slope or cliff), which may originally have been 160 meters in height. The close proximity of the Burgess Shale to the Cathedral Formation may have protected it from metamorphosing (altering) into phyllite (metamorphosed shale).

The fossils of the Burgess Shale have been found in two main sites in the Stephen Formation: the lower Raymond Quarry and the upper Walcott Quarry. The Walcott Quarry, named after the palaeontologist who discovered the Burgess Shale early in the last century, contains the 'Phyllopod Bed' (named after an arthropod with a 'leafed-shaped foot'), a muddy underwater bank now preserved as a lens-shaped formation of shale rocks. Many fossils of various groups of animals have been found in the Phyllopod Bed.
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Section author: Alexei A. Rivera

This section is part of a Fossil Lagerstätten web site which has been built up as a result of the efforts of the 2002-3 MSc Palaeobiology class in the Department of Earth Sciences at University of Bristol, as part of a course in Scientific Communication.

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