Yoho National Park, British Columbia,

Canada, September 8th-13th, 2023



My son James and I visited Yoho National Park with the goal of hiking to two of the most significant Fossil sites in the world; the Burgess Shale and Mount Spephen Trilobite Bed. The Burgess Shale is located on a ridge (known as Fossil Ridge) between Mount Wapta and Mount Field 3000 feet above Emerald Lake. Mount Stephen Trilobite bed is located on a steep terrain 3000 feet above the town of Field. Both sites are off limits to the public but are accessible only with trained professional guides provided by and booked through the Burgess Shale Geoscience Foundation. The fossil beds possess an abundance of extraordinary fossils of hard and soft bodied specimens of the earliest animals dating to the mid-Cambrian, around 508 million years ago. These ancient animals existed in a world much different than our own. During the Cambrian the lands were sterile and all life existed in the oceans. An earth day was 21 hours and an earth year was 420 days. The moon was significantly closer to earth and ocean tides were more extreme. The land contained no soil or vegetation and hence continental erosion was much greater than at present. The sun was weaker however abundant carbon dioxide elevated ocean temperatures to life sustaining levels. Atmospheric oxygen (created by photosynthetic marine bacteria for three billion years prior) was beginning to rise to levels which could sustain the oxidative metabolism of complex animals.


The entire region of what is now the western Canadian Rockies was under a shallow ocean during the Cambrian over 500 million years ago. The marine animals of the Burgess Shale lived either within the water column or at the bottom of the shallow sea bed. Over many millions of years the Cambrian layers were covered with many kilometers of sediment. The area was uplifted to form the Canadian and American Rocky Mountains only relatively recently in geologic time.


Most fossils are mineralized remains of hard parts of organisms (bones, teeth, exoskeletons). Soft parts are rapidly degraded and decomposed making them extremely rare fossils. The remarkable preservation of the soft bodied creatures of the Burgess Shale owes itself to fortuitous geologic events. 500 million years ago, along the west coast of Laurentia (Primitive North America) what was to become the Burgess Shale lay within mudstone deposited at the foot of a huge submarinecliff over 100 meters high composed of carbonate rock (formed by ancient algae) called the Cathedral Escarpment. For over two million years, the marine creatures of the Burgess Shale were quickly buried in sequential submarine mud slides at the base of the Escarpment. The fortuitous conditions which included rapid burial, anoxic environment, and clay mineral attachment to soft body parts, favored extraordinary preservation of the creatures of the Burgess Shale including both their hard parts and soft parts.


The extraordinary variety of animal forms present in the Cambrian rocks of these sites followed what is known as the Cambrian Explosion, a period of about 20 million years (a blink of an eye in geologic time) in which all the major animal Phyla appeared suddenly in the Fossil record. All modern animal phyla are represented by these primitive Cambrian creatures found at these two sites and there have been no additional Phyla added since. There are other sites around the world with similar fossils including Greenland, China, Siberia, and Australia, however the Burgess Shale is the most significant. The Burgess shale fossil beds were discovered by Chales Walcott (at the time Secretary of the Smithsonian Institution) in 1909. From 1909 to 1925 Walcott excavated the fossil beds each summer (now known as Walcott's Quarry) and he shipped in total 65,000 specimens back to the Smithsonian in Washington. Walcott became an authority on Cambrian Fossils however during his lifetime he was unaware of the significance of his discovery. The fossils were reexamined beginning in 1973 by renowned paleontologists such as Harry Whittington, Simon Conway Morris, Derek Briggs, Percy Raymond and Institutions such as Royal Ontario Museum, Geological Survey of Canada, and Harvard's Museum of Comparative Zoology. The reinterpretation of the Burgess Shale led to a revolution in Paleontology made accessible to the public by the best selling book written by Stephen Jay Gould titled "Wonderful Life; The Burgess Shale and the Nature of History", published in 1989.


The Burgess Shale fossils are known to scientists around the world for their abundance, diversity, and wonderful preservation. In 1980 the Burgess Shale was designated as a World Heritage Site by UNESCO (United Nations Educational, Scientific, and CulturalOrganization) which recognizes sites of global significance, to be held in trust by nations for the benefit of humankind. Only 80 world heritage sites exist presently.



A sample of fossils we saw at the two sites

(Quarry Fossils are not allowed to be removed under penalty of law, there are hidden cameras at the quarries

and people have served jail time for removing specimens)


Click on images below for larger images




Trilobites, (Phylum Arthropoda) are abundant at both sites.

They survived as a Class for 250 million Years until their extinction at the end of the Permian.



 Marrella (Phylum Arthropoda), is the most abundant animal found at Walcott's Quarry

 Vauxia (PhylumPorifera) is the most common Sponge found at the Burgess Shale, Sponges predate the Cambrian and likely evolved over 600 million years ago



 Sidneyia, (Phylum Arthropoda) is one of the larger arthropods of the Burgess Shale. It was named after Walcott's second son Sidney.

 Ottoia (Phylum Priapulida) are the most abundant predatory worms in the Burgess Shale




Pikaia gracilens is the oldest chordate known from the Middle Cambrian, Burgess Shale. Chordates gave rise to vertebrates, the sub-phylum we as humans belong to.

(photo courtesy of "The Fossils of the Burgess Shale, Derek Briggs, et al)



 Anomalocaris, the Apex Predator of the Burgess Shale Fauna (grew up to one meter)

 A front appendage of Anomalocaris (used to capture prey)



A Random collection of half billion year old rocks containing

numerous Cambrian fossils (mostly Trilobites)






 Emerald Lake from the Emerald Lake Trail in the Morning


 James at the Walcott Quarry 3000 feet above Emerald Lake


 At the Walcott Quarry above Emerald Lake


 The Town of Field from Mount Stephen Trilobite Bed


About to enter the Burgess Shale Fossil Beds


 Holding one of the many half billion year old fossils found at the Trilobite bed, Mount Stephen



A few Videos from our Hikes

(Click on Pictures below)





 Video from the Trilobite Bed, Mount Stephen, with town of Field 3000 feet below

 Taking a lunch break just before final ascent to Walcott's Quarry

 Video from Walcotts Quarry with Emerald Lake 3000 feet below.





 Site of "Burgess Shale" nestled between Mount Wapta and Mount Field

Yoho National Park, British Columbia (my photo)


 Close up of the Burgess Shale Quarries (my Photo)

Historical Quarries:

Charles Walcott: Original discoverer of the Burgess Shale

Geological Survey of Canada - Commission Géologique du Canada

Percy Raymond, Curator of Paleontology at Harvard’s Museum of Comparative Zoology

Royal Ontario Museum


Books on the Burgess Shale

Wonderful Life, The Burgess Shale and the Nature of History, Stephen Gould, 1989, W.W. Norton.

The Fossils of the Burgess Shale, Derek Briggs, Douglas Erwin, Frederick Collier and Chip Clark, 1995, Smithsonian Institution Press.

The Crucible of Creation: The Burgess Shale and the Rise of Animals, Simon Conway-Morris, 1999, Oxford University Press

Web Sites about the Burgess Shale



 Emerald Lake with Mount Wapta in Background, Yoho National Park, British Columbia