The AAPG Foundation is a proud sponsor of National Earth Science Week, which is held this year from October 13–19. National Fossil Day is next Wednesday, October 16. In celebration, I’ll recognize my favorite fossil, that ‘cockroach of the sea,’ the trilobite. Trilobites can be found in Paleozoic marine rocks around the world. Let’s visit two sites together.
The Walcott Quarry in the Burgess Shale, Yoho National Park, British Columbia
The Walcott Quarry, Courtesy of Callan Bentley
The Burgess Shale, middle Cambrian in age, is a famous stratum containing fossils that show the diversity of life 508 million years ago. This lagerstätte exquisitely preserves the soft tissues of animals with and without hard parts.
History and common fossils:
The site was discovered in 1909 by Charles Walcott, paleontologist and secretary of the Smithsonian Institution. Walcott and his family excavated the site for several summers, using hammers, chisels, and sometimes, dynamite. More than 60,000 fossil specimens were shipped to the Smithsonian National Museum of Natural History.
The assemblage includes four major groups of arthropods (including trilobites), sponges, onychophorans, crinoids, brachiopods, mollusks, worms, and even some of the earliest chordates.
Why it matters: The Burgess Shale reveals the presence of creatures originating from the Cambrian explosion of life. It is a site of exceptional fossil preservation and records a diversity of animals found nowhere else.
Geology of the Burgess Shale:
I had the pleasure of speaking with Professor Callan Bentley, associate professor of geology at Piedmont Virginia Community College, who has taken students on several study abroad trips to the Canadian Rockies, including hikes to the Walcott Quarry. Here are some of his explanations of the geology:
“The Burgess is a member of the Stephen Formation, which is a deepwater shale. Stratigraphically, it overlies the shallow-water carbonates of the Cathedral Formation, but the two are time-equivalent units that are simply different depositional facies.
The different strata can tell us something about the paleo-bathymetry at the site. The ancient slope-break that separated the two is called the Cathedral Escarpment. In the modern day, the boundary between the ‘shallow’ and ‘deep’ facies runs very clearly across the Canadian Rockies, where it’s dubbed the Kicking Horse Rim. The Rim is the modern geo-expression of the ancient escarpment, which divided the platform facies of the Cathedral Formation from the basin facies of the Stephen Formation.
The ‘standard model’ for the deposition of the Burgess Shale (and the preservation of the organisms it contains) is ‘mud avalanches’ off this steep slope, plopping down into the deep part of the basin.”
Learn more about the geology of the Burgess Shale here.
Sponsored
Register Now: Houston Geological Society Golf Tournament 2024
Join us for golf, food, friends, and fun at the annual HGS Golf Tournament at Sterling Country Club and Houston National Golf Club. Register by October 16.
Trilobite from the Burgess Shale, Walcott Quarry, Courtesy of Callan Bentley
Access to the Walcott Quarry is available only through The Burgess Shale Geoscience Foundation. Reservations are required and limited.
The Walcott Quarry trek is one of the most beautiful hikes in the Canadian Rockies, with a view of Takakkaw Falls (the second highest waterfall in Canada) and Emerald Lake. That being said, the 14-mile round-trip hike is very steep and difficult. The hike begins at 5,000 feet above sea level and climbs an additional 2,710 feet in elevation.
No collecting, hammering, or damage of any natural object is allowed. Specimens from locked boxes are shown once you reach the quarry.
There are also easier guided hikes to the nearby Mount Stephen Trilobite Beds. The fossils here are more abundant than at Walcott, but less diverse. The site contains appendages of the Cambrian predator Anomalocaris canadensis, trilobites, brachiopods, and sponges.
Both fossil sites are located in restricted areas within The Canadian Rocky Mountain Parks UNESCO World Heritage Site and are protected by the National Parks Act.
Another, arguably more accessible, option is to dig up your own fossils in Delta, Utah in the Wheeler Shale.
Geology of the Wheeler Shale:
The Wheeler Shale, middle Cambrian in age, was named by Charles Walcott for a major feature in the House Range, the Wheeler Amphitheater. The formation contains interbeds of shaley limestone and mudstone.
Deposition of the Wheeler Shale is similar to that of the Burgess. Close to the shoreline, limestone was deposited as shallow-water reefs. Beyond the reefs, finer sediments settled offshore, sometimes rapidly via undersea landslides off the reef platform.
Some layers of the Wheeler contain abundant trilobites and other shelly fossils, as well as soft-bodied fossils, including many of the same taxa found in the Burgess Shale.
Visiting U-Dig Fossils Quarry:
At U-Dig Fossils Quarry, you pay to dig, and you can keep your finds.
The site is known for trilobites and located an hour west of Delta, Utah. Be prepared to drive on gravel and dirt roads.
The quarry supplies rock hammers and buckets. Bring work gloves, eye protection, a hat, sunscreen, food, plenty of water, and a foam gardening mat to sit on. The rocks are sharp!
I found plenty of trilobites in four hours of splitting the shale—mostly Asaphiscus wheeleri, Elrathia kingii, and one small Peronopsis interstricta—enough to fill three medium flat-rate post office boxes. I’d recommend shipping your finds home.
This laboratory exercise introduces basic anatomy and ecology of the Trilobita. Students will study macroevolution in the fossil record using trilobites as a case study.
The bottom line: These high-quality, reviewed teaching resources highlight Earth Science Everywhere, with tips and tricks for all grade levels.
Many thanks to Callan Bentley for contributing to this week’s newsletter. I challenge all of you to post your favorite fossil on social media for National Fossil Day and use the hashtags #aapgeologists #geolifestyle
Sharon Lyon
Editor, GeoLifestyle
👍 If you enjoyed this edition of GeoLifestyle, consider supporting AAPG's brand of newsletters by forwarding to a friend or colleague and signing up for our other newsletters here.
➡️ Was this newsletter forwarded to you? Sign up for GeoLifestyle here.
AAPG thanks our advertisers for their support. Sponsorship has no influence on editorial content. If you're interested in supporting AAPG digital products, reach out to Melissa Roberts.
