A visit to the Burgess Shale - July 2001

In July of 2001 some friends and I visited the Mt. Stephen Fossil Beds on the east side of the Kicking Horse Valley, and the Walcott Quarry (Burgess Shale) on the west side.  The following are some of the pictures from our visit, along with some comments on the geology of the area.

Click on the small image to see the full-sized image.  Other Burgess Shale resources, including links to other websites, are listed at the bottom of the page.

	The Burgess Shale is a part of the Middle Cambrian Stephen Formation, which is exposed in the Rocky Mountains around Field B.C.  As shown on this geological map, the Stephen Formation (in yellow) overlies the Cathedral Formation (in blue) and is overlain by the Eldon Formation (in grey).  The Stephen Formation is primarily comprised of shale, while the other two are carbonate rocks (limestone and dolomite).  All were deposited in an offshore marine environment around 510 million years ago, when the west coast of North America was around where Revelstoke is today.
	The relationships between these units are shown on this cross section.  The Stephen Formation shale (yellow) was deposited on top of and adjacent to a large underwater cliff of the Cathedral Formation (blue) .  The Burgess Shale (black), which represents a small part of the Stephen Formation, is situated within the thick part of the sequence, below the cliff edge.  Fossil-bearing parts of the Burgess Shale are consistently found close to the boundary with the Cathedral Formation.
	These rocks are all well exposed on the side of Mt. Field, as seen here from the Mt. Stephen Fossil beds.  The Burgess Shale Walcott Quarry is situated just on the other side of Mt. Field, on the pass between Mt. Field and Mt. Wapta.
	Our first hike was up the steep side of Mt. Stephen to the fossil beds in the Ogygopsis Shale.  The fossils here were discovered by construction workers in 1886, over 20 years before the discovery of the Burgess Shale itself.  This view shows the town of Field below, the Kicking Horse River and the trans Canada Highway.  Although you can't see it in this photo, there are so many fossils in the rocks of this area that it is impossible to walk around without stepping on them!
	Our group included about 15 people from various parts of  North America and Europe.  We were guided by a very well-informed geologist employed by the Yoho Burgess Shale Foundation.     It is not possible to visit this site, or the Walcott Quarry, on your own.  Just above this location there is a solar panel and a TV camera.  The park wardens down in Field monitor the site carefully, and there are heavy penalties for unauthorized visitors - and especially unauthorized collectors!
	Although the fossils are super-abundant at the Mt. Stephen site, there are only three main types found here.  These include two different trilobites ( like Ogygopsis shown here), and claws of the predator Anomalocaris.  This fossil is missing the two cheek-pieces on either side of the head, indicating that it is a molt.  It is not the entire animal.
	Both of the common Mt. Stephen trilobites are present in this sample, Ogygopsis at the top, and Olenoides at the bottom
	The other creature found at Mt. Stephen is the very large (by Cambrian standards) predator Anomalocaris.  Some individuals were over 1/2 m long.  For a long time the claws of Anomalocaris (as shown here) were thought to be the body of a small shrimp-like organism - hence the name Anomalocaris or "strange shrimp".  It is now known that these are only the grasping claws of an animal which could be fairly described as the "shark of the Cambrian ocean" (although it was an arthropod, and nothing like a shark).  They are very abundant at Mt. Stephen because they represent molts, and an animal would lose many in its lifetime.
	There are several Ogygopsis molts on this slab of rock, plus a couple of anomalocaris claws - just to the left of the quarter.
	This slate is situated a few hundred metres away from the Mt. Stephen fossil site.  The original bedding planes of the parent shale are visible, at about a 45° degree angle (up to the right).  The slatey cleavage is at about 80° (up to the right).  If the nearby fossil-bearing rock had been this strongly metamorphosed the fossils would have been destroyed.  The fossil-bearing rock was protected from strong metamorphism by its proximity to the hard and strong Cathedral Formation limestone.
	The hikes to the Walcott Quarry start from the Takakkaw Falls area, up the Yoho Valley from Field.  There is no end of awesome hiking and camping in this region - farther up the Yoho Valley, to Twin Falls and to numerous glaciers and crystal-clear lakes.
	On the long hike to the Walcott Quarry we stopped briefly at beautiful Yoho Lake.
	About a kilometre before reaching our destination we came across some good examples of phyllite - metamorphosed shale of the Mt. Stephen Formation.  Again, this type of metamorphism would have obliterated any trace of fossils in these rocks.  As at Mt. Stephen, the Burgess Shale rocks were protected from this by their proximity to the Cathedral Formation limestone.
	Charles D. Wallcott of the Smithsonian Institute, first came to the Yoho area in 1907.  He saw the fossils at Mt. Stephen and, being a Cambrian specialist, he realized that there might be other interesting fossils in the area.  He discovered the Burgess Shale exposure in 1909, and over the next several years excavated tens of thousands of samples out of what has come to be known as the Walcott Quarry.  The quarry has since been enlarged, but Wallcott concentrated on a 2.5 metre thick horizon extending down from the brown layer adjacent to the hand of the person with the white hat. The peak in the background is Mt. Wapta.
	This is another view of the Walcott Quarry, looking in the opposite direction, with Mt. Stephen in the distance on the other side of the Kicking Horse Valley.
	The view directly out from the quarry face is towards Emerald Lake.  The lake's colour is a result of glacial flour - finely ground rock fragments which reflect sunlight in the lake water.  While we were at the quarry there was a paleontological crew from the Tyrell Museum in Alberta camped within the flat clearing a few hundred metres below.
	One of the more common of the Burgess Shale organisms was this burrowing priapulid worm Ottoia.  Ottoia lived in the mud with its head near to the surface, and was ready to reach out and grab any small creatures crawling by.
	There were numerous corals living on the floor of the Burgess Shale seas.  This one is known as Vauxia.
	There were also numerous animals with both single and double shells, including brachiopods and clams.  This single-shell limpet-like animal is known as Scenella.
	One of the best known, and the most abundant of the Burgess Shale creatures is the arthropod Marella.  So many Marella specimens have been taken out that we didn't see many examples, so this one is not that clear.
	Leanchoilia is one of the more curious of the Burgess Shale creatures.  Although this is not a very good specimen, you can see the strange appendages that extend out from the front of his head (to the right).
	Many different types of trilobites lived on the Burgess Shale muddy sea floor.  On this slab there is nice example of an Olenoides (not a molt in this case as it has the cheeks present).  Just next to this guy's left cheek there is another tiny trilobite known as Ptychagnostus.  The Ptychagnostus is smaller than the Queen's head on the nearby quarter.

Web sites

The Yoho Burgess Shale Foundation (go here for information and tours)  http://www.burgess-shale.bc.ca/

The University of Calgary http://www.geo.ucalgary.ca/~macrae/Burgess_Shale/

The Tyrell Museum http://www.tyrrellmuseum.com/bshale/

The Smithsonian Institute's National Museum of Natural History http://www.nmnh.si.edu/paleo/shale/

Books

Wonderful Life, The Burgess Shale and the History of Creation, 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

Steven Earle, Malaspina University-College, Nanaimo B.C., September 2001 http://www.mala.bc.ca/~earles