Discover Canada and Explore the Fossils and Geodiversity of the Burgess Shale of British Columbia
- Wayne Munday
- 4 hours ago
- 5 min read
Sip back and discover Canada and explore the fossils and geodiversity of the Burgess Shale high up in the Canadian Rockies of Yoho National Park in British Columbia. This is one of the world’s most important fossil sites preserving an extraordinary record of marine life from the Middle Cambrian about 508 million years ago. Both the Stephen Formation and Burgess Shale captures soft-bodied organisms with remarkable detail a mode of preservation now termed Burgess Shale-Type (BST). Species such as Marrella, Opabinia, Pikaia and Hallucigenia reveal rare insights into the Cambrian Explosion and the origins of the diversity and complexity of animal life. First discovered in 1909 by Charles Doolittle Walcott, the site includes quarries like the Walcott Quarry and Phyllopod Bed, where tens of thousands of specimens have been collected. Today, the Burgess Shale is celebrated not only for its scientific value but also for its heritage significance and part of the Canadian Rocky Mountain Parks UNESCO World Heritage Site inscribed in 1984 and designated among the IUGS First 100 Geological Heritage Sites. These designations reflect both outstanding scientific value and the broader landscape context of the glaciers, limestone caves, waterfalls and alpine canyons that characterise this 24,000 km² mountain region shared with Banff, Jasper and Kootenay national parks. Guided hikes in Yoho and Kootenay National Parks allow visitors to explore this globally renowned palaeontological treasure.
High in the Canadian Rockies, the Burgess Shale of Yoho National Park, British Columbia, stands as one of the Earth's most important windows into early animal life. Located near to the town of Field and named after nearby Mount Burgess, the Burgess Shale is part of the Stephen Formation and preserves an exceptional marine ecosystem from the Middle Cambrian and the Miaolingian Epoch. The Burgess Shale remains unparalleled record of soft-bodied organisms along with other Cambrian Lagerstätten including the Chengjiang in China and Sirius Passet in Greenland.
The Miaolingian Epoch is the third of four divisions of the Cambrian Period and was formally named in 2018 as the official replacement for the informal “Middle Cambrian” or Cambrian Series 3 dated from 509 - 497 million years ago. The Global Stratotype Section and Point (GSSP) for the Miaolingian Epoch is found in the Kaili Formation of Guizhou, China, marked by the first appearance of the trilobite Oryctocephalus indicus.
The Miaolingian Epoch is divided into the three stages of the Wuliuan, Drumian and Guzhangian in ascending order. This is a time characterised by relatively stable marine conditions following the Cambrian Explosion, with microbial carbonate reefs and largely steady carbon isotope records, disrupted only by minor events such as the Drumian Carbon Isotope Excursion (DICE) between 504.5 - 506.5 million years ago.
During this time sea levels rose flooding continental shelves leading to widespread burial of organic matter and oceans becoming anoxic (lacking oxygen) and euxinic (rich in hydrogen sulfide). This rapid change of oxygen-poor marine conditions led to the expansion of shallow - water carbonate platforms and disruption of marine ecosystems. This epoch provides a critical framework for reconstructing early Paleozoic ecosystems and evolutionary patterns.
The history of the Burgess Shale is intertwined with early 20th-century exploration. Charles Doolittle Walcott, then Secretary of the Smithsonian Institution, embarked upon a systematic collection after learning in 1909 of “stone bugs” uncovered by Canadian Pacific Railway workers in the Kicking Horse Pass during construction of Canada’s transcontinental railway.
There are various fossil hunting locations including the Phyllopod Bed at Walcott Quarry, a 2.3 m thick layer that has produced tens of thousands of specimens from over 150 genera, with shelly taxa making up only 14% of the assemblage. Recent discoveries, such as the 2025 description of the radiodont Mosura fentoni a three eye, spiny swimming organism that resembles a "sea-moth" was found at Raymond Quarry and Marble Canyon highlights the continuing scientific value of the Burgess Shale.
Access is now managed to preserve these sites and the 22 Km trail to the Walcott Quarry on Mount Field requires an authorised guide, while a shorter 7 Km route leading to the Mount Stephen Trilobite Beds is still challenging. Rocky terrain, steep switchbacks and thin mountain air demand fitness and preparation, and guided walks organised by Parks Canada or the Burgess Shale Geoscience Foundation remain the responsible way to experience the quarries.
Walcott’s work and later fossil collecting built a national reference collection now housed in major institutions: the Smithsonian’s National Museum of Natural History, the Royal Ontario Museum and the Royal Tyrrell Museum of Palaeontology. Walcott’s contributions of over 65,000 Burgess Shale specimens are among a broader National Fossil Collection and helped to establish the Burgess Shale as a cornerstone of Cambrian palaeontology.
The Burgess Shale was formed on the ancient continent of Laurentia and the fossils occur within the Stephen Formation a mix of mainly shale with layers of limestone and dolomite. Originally, the Stephen Formation was thought to have been both a nearshore and deep-water deposits but the thinner Stephen Shale Formation is actually part of the thicker Burgess Shale Formation. These formations tell a story of different depositional environments that contributed to exceptional fossil preservation.
The Burgess Shale owes its remarkable fossil preservation to a unique setting along the margin of the Cambrian carbonate platform in the Canadian Rockies. At the base lies the Cathedral Formation, a thick sequence of limestone and dolomite deposited in a shallow-water reef environment. Its steep reef escarpment created a deep basin immediately offshore, setting the stage for fine sediment accumulation. Overlying this is the Stephen Formation, composed mainly of shale with some limestone and dolomite, representing quieter offshore conditions where mud and silt steadily blanketed the seafloor.
Within the Stephen Formation lies the Burgess Shale where largely non-traumatic submarine mudflows cascaded down the Cathedral escarpment, rapidly burying marine organisms in fine-grained, oxygen-poor sediment. This combination of sudden burial and low-oxygen conditions prevented decay and scavenging, allowing even delicate soft tissues to be preserved in extraordinary detail. This “Burgess Shale-type” is a classic Lagerstätte and explains why delicate eyes, gills and gut structures survive alongside durable shells and exoskeletons. Cyanobacterial mats and limited bioturbation further aided fossil preservation.
The Burgess Shale captures a rich benthic community or habitat on and in the sediment of the sea bed of arthropods, lobopodians, anomalocaridids, sponges, ctenophores, cnidarians, echinoderms, hemichordates, molluscs, annelids, priapulids, chaetognaths and abundant microbial life. Iconic taxa such as Marrella, Hallucigenia, Opabinia and Pikaia reveal body plans and morphologies often unlike anything seen in modern oceans. Stephen J. Gould famously called many of these forms “weird wonders” a phrase that still gives the Burgess Shale and possibly the Cambrian Explosion the capacity to challenge traditional evolutionary narratives.
Vertebrate ancestry appears only in stem-forms such as the rare Pikaia gracilens and even rarer Metaspriggina that reveal a hint at the earliest chordate features of muscle blocks that support their back or back sides long before true vertebrae evolved. It is important to note that the Burgess Shale also predates dinosaurs by hundreds of millions of years.
Tectonics and glaciation later exposed these deep-time sediments of the Burgess Shale. Following a period of diagenesis and lithification the Cambrian shales were uplifted, folded and thrust during the Laramide orogeny and subsequently scoured by Pleistocene glaciers that peeled back overlying rock exposing fossiliferous beds at high elevations above 2,300 meters.
