Ayrton finds – and features – the fossils

Urban Geology: The Walk of Life in Calgary

American Association of Petroleum Geologists (AAPG)

State-of-the-art computer software programs enable petroleum geologists to investigate large quantities of subsurface geological data in record-breaking time.

Yet, despite such technological advances, many geologists lament the fact that they rarely have time to travel to the field, that they rarely experience the tactile sensation of laying their hands on outcrops.

But a group of Canadian oil and gas geologists and geophysicists has discovered that a four-hour-long “urban” geology field trip can be just as rewarding as one to the wilds of the Rocky Mountains.

During a recent half-day walking tour of downtown Calgary, Alberta, the geologists (and their friends and spouses) studied the building rocks found in oil company towers and historic churches and hotels.

In the process, they learned about the history of Canada’s oil and gas industry, discovered the existence of two-foot long fossils and were exported to exotic locales around the world, viewing building stones ranging in age from the Precambrian to the Tertiary eras.

Kneeling down to examine polished floors in oil company towers, the enthusiastic group – equipped with backpacks, hand lenses and acid bottles – attracted the attention of security guards who, on a couple of occasions, asked the group why they were taking photos.

Developed and led by AAPG member Bill Ayrton, the “Building Rocks of Calgary Geological Walking Tour” often is used by the Calgary oil and gas industry as a team-building exercise.

President of Ayrton Exploration Consulting Limited, Ayrton’s oil and gas career has spanned more than 40 years.

“People tell me that the field trip has changed the way they walk around downtown,” said Ayrton, a former president of the Canadian Society of Petroleum Geologists. “I usually apologize to them, saying, ‘Now, you’re going to be late for work.’

“People are fascinated by what they see in their own back yards,” he added, “and even in their elevator banks.”

It Begins With the Rocks

Ayrton’s tour examines the rocks, sedimentary features and fossils found both inside and outside the buildings of Calgary.

Building stones include locally quarried sandstones and spectacular varieties (igneous, metamorphic and sedimentary) from as far away as Scandinavia, Italy and India. Polished slabs and differential weathering of exterior surfaces reveal textbook geological features, including cross-bedding, porosity, stylolites, fossils, burrows, vugs and euhedral crystals.

Ayrton described the oil and gas companies’ imposing lobbies, with their impressive use of imported marbles, travertines and granites, as their “calling cards.”

The oil strike at Leduc, in 1947, he said, heralded the beginning of the Alberta “gold rush.” Since then, Calgary’s skyline has kept pace with Alberta’s oil and gas discoveries, climbing from low rises to high rise towers topping 60 stories.

Historical aspects aside, Ayrton pointed to other compelling reasons for petroleum geologists to participate in the urban geology field trip:

“I firmly believe that in the oil and gas industry, everything begins with the rocks,” he said. “Today geologists are transfixed by working on computers – but we don’t get rock descriptions from computers.”

Spotlighting Some Real Gems

The geological field trip was sponsored by CMAGS, the Canmore Museum and Geoscience Centre, a not-for-profit organization located a one-hour drive west of Calgary.

Dedicated to geoscience education, CMAGS mounts exhibits and designs programs that showcase the human and geological stories of the Rocky Mountains.

Rick Green, AAPG member and president of CMAGS, described the building rock field trip as a perfect teaching vehicle to educate the organization’s broad audience – geoscientists, teachers, students, families and tourists.

Green, a petroleum geophysicist, characterized the inaugural building stone field trip, comprised of eight students led by Ayrton, as a “huge success.”

“I saw a much wider range of fossils than I could see in the mountains, in any given field trip,” Green said. “You can walk around downtown Calgary and view great specimens up close.

“These secret gems are hidden from view, from passersby, unless you know that they’re there,” he added. “And Dr. Ayrton brought these gems out.”

The group of intrepid explorers was fascinated by the “gems” found in the many buildings constructed of Ordovician age Tyndall Stone. Chock-a-block full of trace fossils – dendritic patterns of burrows left by ancient sea critters – Tyndall Stone also contains corals, gastropods, bivalves, brachiopods, nautiloids, bryozoans, stromatoporoids, trilobites and calcareous algae. Field trip participants lined up for photographs beside a particularly well-preserved nautiloid that measured two feet long.

Still quarried in Garson, Manitoba, Tyndall Stone’s distinctive – and much sought-after – mottled texture led to its use in Canada’s parliament buildings and in the grand hotels built by Canadian Pacific Railway along its scenic route through the Rocky Mountains.

“Tyndall is an absolute graveyard; it’s a fossil hash,” Ayrton exclaimed as he applied (sparingly) hydrochloric acid on an exterior wall, demonstrating the phenomenon of selective dolomitization – the darker colored (burrowed) sections of the mottled stone are dolomitic while the lighter colored sections which are calcitic.

‘An Eye-Opener!’

Because the fossils also are dolomitized – and thus more resistant to weathering – they are prominently featured in the Tyndall Stone’s limestone matrix.

“Not many people would think of doing a geology field trip in Calgary, and it was surprisingly interesting,” said Brent MacDonald, CMAGS’ earth science coordinator responsible for developing educational outreach activities targeting K-9 students.

The walk-about provided MacDonald with innovative ideas for hands-on student activities, ranging from scavenger hunts, draw-the-fossil-on-the-wall competitions (using tracing paper, of course), stratigraphic columns, palaeontology, the oil and gas industry, history and architectural styles.

Retired geologist Lemuel MacDonald, a member of the CMAGS board of directors, was on the hunt for one of the rare fish fossils found in Tertiary age Paskapoo Sandstone, called the building stone field trip an “eye opener.”

In 1886, after a fire destroyed Calgary’s nascent pioneer town, fire resistant sandstone replaced wood as Calgary’s primary building material.

“It was mandated after the fire that all public buildings had to be made of Paskapoo Sandstone,” Ayrton said.

During the early 20th century, 15 local quarries provided Paskapoo Sandstone for public buildings and for the grand homes constructed of brick and decorated with ornamental sandstone. Shedding its pioneer beginnings, Calgary emerged from the fire and became known as “the Sandstone City of the West.”

MacDonald was struck by variations “durability” between the Paskapoo Sandstone and the non-porous granites, which have a natural polish.

“The sandstones were clearly weathering at Knox United Church,” he said, “the result of the porous rock absorbing moisture.” Opened in 1912, Knox United was constructed of cross-bedded Paskapoo Sandstone, which is prone to freeze and thaw during weathering processes.

A Perfect Ending

Not parting with tradition, the group of intrepid explorers finished off the geological field trip with a cold beer or two.

Fittingly, the group chose to patronize the Sandstone Bar in the Hyatt Regency Hotel, a modern building that spans a city block and boasts the original sandstone and brick façades built in the early 1900s.

As for Lemuel MacDonald, at his leisure and during the summer months, he’ll continue to explore the Sandstone City’s numerous historical buildings, in search of elusive fish fossils.

For more information on Ayrton’s walking geology field trip go to cmags.org, and ayrtonexplortion.com/course6.htm.

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