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Our Travels: Finding Fossils in the Burgess Shale

Rock Stars: Exploring the Burgess Shale in Yoho National Park

My shoulders were burning with the weight of my pack. Sweat was rolling down my face, stinging my eyes. My lungs were working overtime from the last steep push to the top. But even with all my bodily discomfort, those final paces were significant as they followed in the exact footsteps of Charles Doolittle Walcott, the man responsible for discovering the Burgess Shale. The soreness seemed to just melt away as I caught my first glimpse of the famous fossil bed. My sole purpose for being 2,286 metres (7,500 feet) above sea level, perched on the side of a mountain ridge, was this exact spot: Walcott’s legendary quarry. It took only a matter of seconds for my eyes to spot a lone fossil peeking out from among the broken shale and from that point I was hooked.

The Burgess Shale has been called one of the most important fossil discoveries anywhere on the planet. The fossils found there are more than 505-million-years-old and are some of the finest examples of soft-bodied preservation anywhere on Earth. Most fossils on record contain hard body parts, such as bones, shells and teeth, but the ones discovered in the Burgess Shale also contain mineralized soft tissues, allowing us to see the entire organism completely preserved. Half-a-billion years ago, the geography that is now Yoho National Park was very different. There was no British Columbia, no Canada, not even a North America. The entire area was under the ocean and all life on our planet resided below the surface. The exceptional fossils of some bizarre-looking creatures include some of the oldest known relatives of many species still alive today. These primitive creatures lived near the muddy sea floor. At different times, these animals would be caught in underwater mudslides, becoming buried in deep water away from scavengers. The mud and silt that entombed them was so fine it was able to settle between each curve and crevice of the organism’s body. Additional layers of mud and silt were deposited on top, slowly flattening the entrenched animals. Over time and through various geological processes, the mud and silt hardened, eventually becoming shale, preserving the trapped inhabitants for eternity.

Like champagne bubbles, Viagra and Velcro, the Burgess Shale was also discovered accidentally. In the late 19th century as the Canadian Pacific Railroad was moving westward through the difficult Kicking Horse Pass region, one railroad employee found what he described as “stone bugs” on the steep slopes of Mount Stephen. Those “bugs” turned out to be trilobites and there were millions of them. The stories of the stone bugs eventually made their way to geologists from the Geological Survey of Canada, bringing scientists out west to study the site, collect specimens and publish reports about their findings. One of those reports caught the attention of Walcott, a fossil enthusiast and secretary of the Smithsonian Institution, although he didn’t visit the famed trilobite bed until 1907, a full 20 years after first reading about it.

Two years after his initial visit, Walcott was back in British Columbia in search of more fossils, but here’s where history gets a little murky. While riding his horse on a high trail between Wapta Mountain and Mount Field, Walcott encountered a large rock in his path. He was either bucked off his horse or got off to move the boulder out of the way. How he got off his horse isn’t as important as what he discovered once he was on the ground. Had he not dismounted his horse that fateful afternoon, the small fossil he found would have likely gone undiscovered awhile longer. That early specimen would become the first of many collected from Walcott’s Quarry in the Burgess Shale, so whichever version of history you prefer, it was a defining moment either way.

Walcott and his family would spend at least a portion of every field season in the Canadian Rockies from 1907 to 1924, uncovering new organisms, many of which were previously unknown to the scientific community. It was Walcott who determined the fossils were from the Middle Cambrian Age, making them over half-a-billion years old. Throughout his time in the Rockies, he would identify many new species and provide expertise on the area and its prehistoric organisms. By 1924, Walcott assumed he had exhausted his quarry and didn’t return the next year. Unfortunately, he died in 1927 leaving the 65,000 fossils he’d collected all but ignored for the next 40 years. Ultimately, his collection would become one of the jewels of the Smithsonian Institution’s permanent collections at the National Museum of Natural History in Washington, D.C.

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