As someone who teaches paleontology, I am used to looking at rocks. On my daily walk home from the Redpath Museum in Montreal, where I work, I began to notice that fossils were “hidden in plain view” in the construction materials of some iconic downtown buildings. I set out to discover as many
as I could, and to bring to light this fascinating corner of intersection between the world of natural history and the history of the built world.
The stories of the animals preserved in building stone begin in deep time, about 500 million years ago, when most of eastern Canada was submerged under a rich, nutritious, and well-lit coral sea and the overall landscape of North America probably resembled that of the present-day Atlantic coast. What is now Montreal, Ottawa, Quebec City, Sherbrooke, Toronto, and Kingston was a shallow tropical sea, the precursor of the Atlantic Ocean, teeming with life. Officially named the Iapetus Ocean by Canadian geophysicist John Tuzo Wilson in the 1960s, this sea was home to thousands of different kinds of invertebrate animals. The tiny dissolved shells and animal fragments that were deposited at the bottom of the sea eventually formed a layer of limestone known locally as Montreal or Trenton limestone. This layered stone is almost a quarter of a kilometre thick. All the weird and wonderful soft-bodied animals that lived in the Iapetus Ocean are buried in the bedrock platform of most of southeastern Canada. This is the grey stone in which most of our story resides, with fossils preserved in a few of the older buildings in the core of downtown Montreal.
You can begin your viewing of these fossils at Canada’s oldest museum, the Redpath, built in 1882 with funds from the Redpath Sugar family and located inside the McGill University campus. Near the back door, you can spot fragments of busted white shell with fine “ribs” or stripes cushioned within the foundation stones. These shells belong to a group of animals called brachiopods. Paleozoic brachiopods were filter-feeders and could swim in the jet-propulsion style like modern scallops. Geologists will tell you that more than 12,000 different genera of brachiopods thrived in the ancient Iapetus Ocean. Today they seem rare: about 300 species make their homes in very cold water, either in polar regions or at great depths.
Ancient sea snail shells can be found stuck into the stone wall surrounding the Mount Royal Club located at 1175 Sherbrooke West. Built with Trenton or Montreal limestone quarried from St. Marc’s near Quebec City in the late 1940s, this wall is chock-full of the remnants of ancient sea snail shells. They surface like interlocking Spirograph drawings strapped into the dark grey pock-marked matrix. The entire wall shows only one species, the hollowed-out gastropod moulds from the sea snail called Maclurites. Gastropods were common in the Ordovician Period (from 530—465 million years ago) and are one of the most successful animal groups today, with well over 60,000 species living in the seas, fresh-water, and on land, from the equator to near polar conditions.
Preserved in the stone entrance staircase at Maison Peter Lyall, 1445 Bishop Street, you will find the remains of “moss animals.” The house was built in 1889 for the engineer of Canada’s Houses of Parliament and his family with “Old Red Sandstone” from Scotland, a distinctive rock formed in the Devonian Period, about 260 million years ago. Scottish sandstone or brownstone is uncommon in Montreal. It was used as ballast to stabilize empty ships transporting goods and resources such as fur during the 18th and 19th centuries. Some of the ballast was dumped at the port of Montreal and developers/planners would use it for building stone, as was the case for the Peter Lyall house, because it was very cheap if not free. The exterior staircase is made of Chazy Formation limestone (a geological subdivision of the Trenton limestone) and the little marks that look like broken branches of wood are the fossil remains of animals called bryozoans. (Their common name comes from the Greek for “moss animalcule.”) Bryozoans are small colonial animals that create a branching skeleton of calcium carbonate on hard surfaces. Bryozoans arose during the Ordovician and still exist today, forming most coral reefs.
Also of note are the carved sandstone heads under the windowsills. Most of these carvings are protected by the window ledges but some of them have weathered badly and most of the detail of the face is missing. This weathering is due to the chemical alteration of feldspars to kaolin (clay) under the influence of acid present in snow and rain.
If you take a little side trip up de la Montagne Street north of 1321 Sherbrooke Street West, the showiest fossils are displayed in the east wall of Le Château Apartments, a building commissioned in 1923 by Pamphile Réal Du Tremblay, the owner of La Presse newspaper. Its façade forms an imposing fortress made almost exclusively with Tyndall limestone quarried from the tiny town of Tyndall, Manitoba. Like the Montreal limestone, it is Late Ordovician in age and was formed from sediments laid down approximately 445 million years ago. The dominant predator in this sea was the orthocone cephalopod, a mollusk that looked like a squid in a protective shell. These large predators used their strong tentacles, which enfolded a snapping beak-mouth, along with powerful jet propulsion, to capture trilobites. The fossilized shell of this cephalopod is the most common fossil preserved within the Tyndall limestone.
The Tyndall limestone of the apartment building, known in the quarrying trade as “Tapestry rock,” has a distinctive mottled appearance and is popular in the construction or facing of many of Canada’s proudest institutions. The Houses of Parliament in Ottawa and the Legislative Buildings in Winnipeg, Regina, and Edmonton, as well as the Canadian Museum of Civilization in Gatineau are prime examples. When fresh, the material is light grey with darker grey to brown mottles and it weathers over time to a pleasant creamy yellow or gold colour with russet-coloured mottles. The mottles are actually fossils. They are traces of burrows made in the original sediment by an unknown animal; the disturbed sediment within the burrows has been preferentially dolomitized at a later date making it darker and more resistant to weathering. Ghost shrimp in the Caribbean Sea make similar burrows today, so it is possible these animals were an ancestral burrowing shrimp.
Our final preserved animal is found in the side wall of McGill’s Faculty Club located at 3450 McTavish Street. Built with Trenton limestone on the street side, a “trace fossil” is located in the red clay bricks on the northside wall adjacent to the driveway. When these bricks were made in La Prairie Brickyards, located on the southwestern shore of the St. Lawrence, about 20 kilometres from Montreal’s downtown, more than 100 years ago, the clay was left to dry in moulds rather than being baked in a kiln or fired. Cats walked over the wet bricks and left their paw prints on them. This is not a fossil but it still gives us a sense of how ornamental stone continues to delight and surprise, in the most unexpected ways.
Excerpted from Fall/Winter 2013 Ornamentum. Click here to subscribe.
Ingrid Birker is the Science Outreach Administrator at Redpath Museum in Montreal.
More information is available in the booklet What Building Stones Tell: A Walking Tour focusing on the fossils, rocks and minerals of Montreal Buildings (2002), available in hard copy from the Redpath Museum (email Ingrid.firstname.lastname@example.org to place your order) or in an on-line version at www.mcgill.ca/redpath/resources/fossils/buildingstones/
Clockwise from left:
Fossil bryozoan and rugose or horn
coral on Le Château Apartments, Montreal
Sea snail shell fossil on perimeter
wall of Mount Royal Club, Montreal
Orthocone cephalopod on
Le Château Apartments, Montreal
Edge of fossil sunflower coral on
Le Château Apartments, Montreal