The Burgess Shale

The Locality Today

Panoramic view of mountains
Aerial view showing Wapta Mountain (left) with the main Burgess Shale sites (WQ: Walcott Quarry; RQ: Raymond Quarry; CQ: Collins Quarry).

The Burgess Shale refers to a fossil-rich locality on Fossil Ridge between Wapta Mountain and Mount Field, just a few kilometres north of the small town of Field, British Columbia. Charles Walcott coined the term to describe various fossiliferous rock layers with soft-bodied preservation that he found in 1909 and 1910 and excavated for several years thereafter. The most important excavations were made within a two-metre-thick section representing a series of layers containing the most exquisitely preserved soft-bodied fossils. This section was named the “Phyllopod bed” by Walcott, in reference to the leaf-like structure of the appendages of certain abundant arthropods, including Waptia.

Left, a dark-coloured fossil; right, an excavated quarry
Left, Marrella splendens, (size = 16 mm) a common fossil from the "Phyllopod bed"; right, the limits of the Phyllopod bed are indicated by a double arrow.

Walcott excavated the Phyllopod bed for several years, leaving what is known today as the Walcott Quarry. This quarry has been expanded by subsequent excavations, in particular by the Geological Survey of Canada and the Royal Ontario Museum.

The Walcott Quarry remains the best-known Burgess Shale site, but is far from the only one. Among the 65,000 Burgess Shale specimens collected by Walcott (mostly from the Phyllopod bed) a few came from rocks about 22 metres higher on the slope. These layers were later excavated by Percy Raymond in 1930 and are now referred to as the Raymond Quarry.

New layers were also excavated below the Walcott Quarry and above the Raymond Quarry by the Royal Ontario Museum in the 1980s. The most important new horizon there – about 40 metres above the Raymond Quarry – is now referred to as the Collins Quarry. Additional soft-bodied fossils can be found in various layers between each of these quarries, but have not yet been collected systematically.

In summary, the different quarries of the Burgess Shale on Fossil Ridge represent various fossil assemblages within a body of shale roughly 100 metres thick, marking a history of fossil deposits covering about 200 000 years of the Cambrian Period.

Fossil Ridge with the various Burgess Shale quarries next to the Cathedral Escarpment

The Trilobite Beds on nearby Mount Stephen also contain fossils of soft-bodied animals (e.g., AnomalocarisWiwaxia) that were discovered in the area in 1886, long before Walcott discovered the original Burgess Shale site on Fossil Ridge. Today, scientists refer to the Trilobite Beds as a Burgess Shale-type locality. This site is of a similar age and within the same geological formation as the Burgess Shale quarries on Fossil Ridge. More importantly, its mode of fossil preservation is also comparable – although it is not part of the original Burgess Shale site on Fossil Ridge proper.

Main Burgess Shale-type deposits in the Canadian Rockies.

In addition to the main quarries on Fossil Ridge and the Trilobite Beds, other locations with Burgess Shale-type fossils have been found in the Canadian Rockies, most within the boundaries of National Parks close to a geological feature called the Cathedral Escarpment. Various sites are known in Yoho National Park, including Mount Field, Mount Stephen (Tulip Beds – S7Collins Quarry on Mount Stephen), Mount Odaray and Park Mountain. Kootenay National Park contains Burgess Shale-type deposits in the Stanley Glacier and The Monarch areas, while Burgess Shale-type fossils have also been found in Jasper National Park and outside the parks near Cranbrook, British Columbia.

These different fossil assemblages differ in species composition and abundance of specimens, but represent elements of a similar biota.

Photograph of Mount Stephen, indicating locations of major fossil deposits
Different Burgess Shale-type deposits on Mount Stephen. CQ: Collins Quarry, TB: Trilobite Beds, S7: Tulip Beds (S7).
Photograph of glacier spilling into mountain valley
General view of Stanley Glacier in Kootenay National Park. This area has yielded Burgess Shale-type fossils.