Turning over half-billion-year-old stones at the Manitoba Museum

By Dr. Graham Young, past Curator of Palaeontology & Geology

The Deep History of the Churchill Quartzite 

As we pass through life we accumulate scars, each of which tells a story about an event that affected us. This white line on my hand shows where I fell hard on a tree stump in Nova Scotia when I was 19 years old. That pain in my ankle reminds me of an injury from another fall 30 years later, on an oil-slicked seashore. The older we get, the more of these old scars and injuries we will accumulate.  

It is the same in the natural world. Very old natural things, whether they are living or inanimate, carry many sorts of evidence with them. In the case of rocks, this evidence can tell us the stories of all the events that affected a rock between the time it was formed and the present day. 

Manitoba is home to many very old rocks; at least 2/3 of our province has bedrock that is about 1.7 to 3.5 billion years old, dating from the mid part of Precambrian time. Many of these rocks are beautiful and memorable – consider examples such as the granites and schists of the Whiteshell, east of Winnipeg – but to my eye the most memorable is the Churchill quartzite. This is the blue-grey to dove grey stone that forms the sculptural, sinuous “whaleback” ridges on both sides of the mouth of the Churchill River near Hudson Bay, so often seen as the backdrops in photos of polar bears. 

The Churchill quartzite has long been remarked upon by visitors to the Churchill area. It was first described and named by the Geological Survey of Canada geologist Robert Bell in 1880, and though the name “Churchill quartzite” was assigned so long ago, it has never received a formal scientific description, so the word ”quartzite” is not capitalized.  

The first waypoint of Churchill quartzite’s time travel was its formation. Although it is a “youngster” in comparison with some of the Precambrian rocks east of Lake Winnipeg, it is still deeply old. Somewhere around 1.8 billion years ago, what is now the Churchill area was covered by large rivers that flowed from newly rising mountains nearby. Since the riverbeds were steeply sloped, the rivers carried an abundance of coarse sediment: quartz grains, dark minerals such as mica and magnetite, and fragments of various rocks (some of which could be quite large). 

Where the flow of those rivers slowed, they deposited sediment. The Churchill quartzite contains evidence that it was deposited by flowing water, and that the flow was variable: features known as cross beds were formed as the sediment was laid down on angled or curved surfaces, in places such as river sandbars. Over long intervals of time, this deposited material was buried in more sediment, and pressure from the weight of that sediment turned it to stone. The sand, varied minerals, and rock fragments formed a dirty sandstone, known geologically as a greywacke. 

Through yet more geological time, this greywacke was buried ever deeper, where it was subjected to heat and pressure from the ongoing geological activity in this region. This welded the sediment grains together, giving the rock the remarkable toughness for which it is prized today by people building railways and airports. The greywacke had been metamorphosed and became a metamorphic (changed) rock, the metagreywacke that we call the Churchill quartzite. 

As time continued to pass, the nearby mountains were worn flat by erosion, and the tough, deeply buried Churchill quartzite was slowly uplifted until it was again exposed at the Earth’s surface. For many millions of years, this bedrock was subject to the forces of erosion in a desert-like landscape; the rock surfaces were smoothed and weathered, and large boulder fields developed at the bases of quartzite slopes. 

More than a billion years after the Churchill quartzite was formed, another waypoint was added to its time journey. The Churchill region was now near the equator, and a warm sea flowed in and covered the area. Water extended to the horizon in all directions, but the tough ridges of quartzite stood up above the water, so that they formed an archipelago of islands in that tropical sea. 

Around these islands, abundant sea life lived: creatures such as trilobites and giant cephalopods swam in the water, while corals proliferated in front of and against the quartzite shores. We see evidence of this sea life in Ordovician and Silurian age dolostones (rocks similar to limestones) and sandstones that date from about 450 to 440 million years ago; in some remarkable instances the fossil-rich rocks fill crevices in the quartzite surfaces!  

The sea became deeper, and during the Silurian and the subsequent Devonian Period, it is likely that the sculpted ridges of Churchill quartzite were again buried, with hundreds of metres of sedimentary rock laid down above them. An immense length of time passed, hundreds of millions of years, the sea was gone, and the thick sedimentary rocks above the quartzite were slowly eroded away by water and wind. 

About two and a half million years ago, a different erosional force arrived in the region. The Ice Age, also known as the Pleistocene glaciation, began, and large continental glaciers began to expand southward from the Arctic. These glaciers eventually covered much of North America, and in places they were two to four kilometres thick! The immense weight of this great thickness of ice gave it immense erosional power, and as it moved slowly southward across the land surface it deeply eroded and scoured the bedrock surfaces. 

As was the case during earlier erosion intervals, the immense toughness of the Churchill quartzite meant that it fared better than the other rocks around it. The dolostones that overlaid and abutted the quartzite were heavily ground down, to the extent that they can be observed in only a few select places in the Churchill area. The quartzite ridges themselves, in spite of their hardness, show considerable evidence of glacial erosion: in most places their surfaces were polished by the ice and show striations, lines and grooves that demonstrate the varied directions of ice flow as the rock fragments stuck into the bottom of the glacier scraped the top of the bedrock. 

In some locations you can see other features characteristic of glacial erosion: a roche moutonnée, or sheepback, shows where a large chunk was plucked out of the downstream side of a quartzite ridge, while the upstream side of the same ridge was smoothly polished. Chatter marks are smaller features, crescent-shaped gouges that show evidence of chipping by rock fragments on the base of the glacier; these are typically at right angles to the direction of ice flow (which is itself demonstrated by the striations, or lines on the bedrock surface). 

In southern Canada the Ice Age began to end roughly 12,000 years ago, and by 8,000 years ago the ice in northern Manitoba had melted to the extent that the Tyrrell Sea had formed – this forerunner of Hudson Bay was a huge body of water that covered the low-lying land that had been pushed down by the weight of the glaciers. Our ridges of Churchill quartzite were now again under deep salt water; old beach ridges show that the Tyrrell Sea extended many tens of kilometres south and west of Churchill. 

This region has been rising ever since, and even today the Churchill area continues to rise at a rate of almost a metre a century! This continued uplift is shown by the relationship between some human structures and the quartzite ridges. For example, old mooring rings at Sloop Cove, near the Churchill River, show where people were able to haul sloops (small ships) out of the river in the 18th century, to protect them from ice during the long northern winter. The cove has risen so much in the past 300 years that there is no way a ship could be hauled out in the same place today! 

Sloop Cove is one piece of the final chapter in the saga of the Churchill quartzite. The sinuous ridges have actually been associated with humanity for several millennia, ever since Pre-Dorset Inuit people living some 3500 years ago hunted marine mammals from what was then an archipelago of quartzite islands in the Tyrrell Sea. More recently, the men of the Hudson’s Bay Company quarried large blocks of this tough stone for construction of the impressive 18th century Fort Prince of Wales and Cape Merry Battery, which flank either side of the mouth of the Churchill River. Those men also carved the names of many men and ships into the cross-bedded quartzite at Sloop Cove. 

In the 20th and 21st centuries, Churchill quartzite has been put to many uses by enterprising humans: it makes superb ballast stone for the Hudson Bay Railway, it has been used to construct the large weir that controls flow of the Churchill River, it underlies the runways of Churchill Airport, and it appears as a backdrop in all those wonderful photos and videos of polar bears in their natural habitat! 

What does the future hold, I wonder, for such a remarkable and robust geological formation? In any case, it will be here for many millennia to come. 

This post draws on images and observations from our very successful August, 2022, Museum research trip to the Churchill area, which allowed our group to develop many ideas for new exhibit collaborations. A few of the photos are from earlier paleontological fieldwork in the Churchill area over the past 26 years.  

By Dr. Graham Young, past Curator of Palaeontology & Geology

Bison rubbing stones are icons of the prairies. These large stones were originally transported south by Ice Age glaciers, then left behind on the prairies when the glaciers melted and receded roughly 12,000 years ago. They are therefore considered to be a form of fieldstone, and such large blocks of fieldstone are commonly called glacial erratics.

In the millennia since the glaciers left this region, rubbing stones have undergone a lengthy and intensive polishing process. These are boulders that were tall enough that they were made use of by itchy bison, who needed to shed their heavy winter coats or scratch after being bitten by flies and mosquitoes. The rubbing by bison over such a long time interval, along with the oils from the animals’ hides, gives rubbing stones a distinctive patina, and a rubbing stone is typically surrounded by a ring of flattened, eroded earth.

For our new Prairies Gallery, we knew that we wanted to include this sort of defining prairie element as a full-sized touchable piece, but we also knew that a cast or sculpted stone just wouldn’t do it. We had to acquire a real stone, and it had to be light enough that it could be moved into our gallery and placed safely on the gallery floor for an indefinite period of time. Since the gallery’s weight allowance is quite limited, how could this possibly be done?

As was the case for our fieldstone wall, we discussed this with stonemason Todd Braun quite early in the gallery development process. Although we thought that there should be a real boulder in the gallery, we also knew that it could not be a recognized rubbing stone, as those are heritage objects that should be left undisturbed in their original locations. Instead, Todd suggested that he could acquire a boulder of suitable size and rock type from gravel pits in the Morden area, and that he would prepare the boulder so that it could meet the floor loading limits and other requirements for placement in our gallery.

Todd told us that we were getting our money’s worth, since the job was more work than he had anticipated, but the hollowing out was completed by late November. He was also able to put a bit of a polish on the outer surface of the stone, to mimic the effect of rubbing by thousands of bison.

Todd used his tractor to lift the boulder into the back of his truck. Very early one morning, he drove to Winnipeg before there was significant traffic on the roads. The truck was backed into our loading dock, the hoist was attached to the heavy-duty straps that Todd had placed beneath the boulder, and the stone was lifted very smoothly onto a pallet jack. We were grateful at this stage that the boulder had lost so much of its original weight!

We had a crew of four on hand to assist Todd with moving the boulder into the gallery: an expert construction manager, and three curators to provide the grunt labour. Since we had measured all the doorways and halls in advance of this move, we knew that there would be a few tricky spots during the stone’s travel through the building, but that it should just fit through all of those.

First, we trundled it down a long corridor and through the Museum’s workshops, then out into the Welcome Gallery. Since there was new flooring in the galleries, we had to begin laying down sheets of board when we left the workshop space. There were several large plywood sheets, so it was a matter of laying down a row of boards along the planned path, then lifting each board after we passed over it, and moving it to the front of the other boards so that there would always be a safe surface for the pallet jack.

The stone turned out to have a bit of a “mind of its own” when it came to the direction our route would take, and there was some manoeuvring required to get it lined up with the doorway that would take us into the Winnipeg Gallery area. This gallery was another tight spot, and after some discussion and changing of direction, the boulder slipped through. We then had a clear run to its final location by the Pronghorn Diorama.

By Dr. Graham Young, past Curator of Palaeontology & Geology

Beginning in 2012, The Museum’s curators worked together to plan exhibits for the Bringing Our Stories Forward project (BOSF). As we travelled around the grasslands region to prepare ideas for our new Prairies Gallery, we developed a list of topics that would be essential for a representation of this region. We rapidly agreed on some things that had to go into the Gallery: prairie vegetation, the importance of wind, Indigenous prehistory (and most particularly mound-building cultures), and several other topics. One of these was fieldstone. 

What is fieldstone, and why did we think it was essential? 

When European settlers arrived on the prairies, they wanted to build permanent houses and other buildings. They were now in a region where there were almost no trees away from the river valleys, so material for wooden houses could be scarce. Many settlers came from parts of Europe where houses were built from stone that was quarried from solid bedrock, but on the Manitoba prairie the bedrock was either buried far below the land surface, or it was soft Cretaceous shale that was useless as a building stone. 

There was however, a building stone resource that was readily available: loose fieldstone boulders, which lay on the land surface or could be readily found by digging near riverbanks. Fieldstone is a mixture of many kinds of stone. These stones formed as bedrock at  different times, under varied conditions, and include igneous, metamorphic, and sedimentary rock types. 

Like the settlers, fieldstone had immigrated to the prairies. During the Ice Age (Pleistocene Epoch), huge glaciers covered Manitoba. Glacial ice flowed southward, pulling blocks of stone out of solid bedrock. Blocks (glacial erratics), left behind when the ice melted, are used as fieldstone. Most fieldstone thus originated far to the north of where it is found today. 

Since fieldstone was a distinctive natural material seen across many parts of the prairies, and since it was used by settlers when they built many of the early buildings, it was clear to us that the fieldstone story should be included in our Prairies Gallery. We already planned to build an exhibit about the Brockinton National Historic site, a significant precontact bison kill site in the Souris Valley south of Melita, so it made sense that we also create an adjacent exhibit that would represent a wall of the Brockinton house, a late 19th century structure that sits at the top of the slope above the archaeological site. 

But how could we build this exhibit? Stone is really dense, and a mass of solid stone would have been far too heavy to be supported by the floor in our gallery space. Stone is also not really a topic that would have been suited to an animated video like our beautiful Prairies Mural Wall, and a flat panel display would have been just that: flat. We needed some way to allow visitors to observe and touch the genuine stone, in a setting that imitated a real fieldstone wall.  

Fortunately, in our various travels around southern Manitoba we had met Todd Braun, a stonemason who works in the Altona area. By consulting with Todd and with our exhibit design team, a plan took form: a frame would be fabricated from steel clad in plywood, and Todd would prepare the stones to attach to that frame, reducing their weight by slicing them thin. 

Todd and I selected stones to represent the great variety of fieldstone seen in southwestern Manitoba. Many of these came from boulders and cobbles that Todd had found during his visits to various gravel pits. A few were rocks that we found together, and in one or two instances I went to other geologists to request examples of very particular rock types.

Once we had agreed on the stones to be used, Todd prepared them using traditional techniques, breaking each rock with a hammer until it had a blocky shape. These blocks were laid out in their approximate relative positions for the wall. After a fitted layout was achieved, Todd patiently took each block and trimmed it with a saw so that the visible surface was effectively a “veneer” with only a few centimetres of thickness. These veneers were then attached to the steel and plywood frame using adhesives and metal hardware, and the space between them was covered in traditional mortar. The “corner stones” were a particular challenge, since they had to be cut in such a way that they would look like solid three dimensional blocks once the wall was assembled. 

To allow the wall to be assembled in Todd’s workshop prior to its installation in our gallery, the frame was actually built in three sections. This made each piece light enough to be readily moved, and small enough to fit through the smallest doorway between the Museum’s loading dock and our new Prairies Gallery. Very early one morning, Todd arrived at the Museum with the completed wall sections on his trailer. These were hoisted into the loading dock, and rolled through the Museum to the wall’s permanent gallery location. Todd and our construction team had created an ingenious hoist system that would allow each upper wall section to be lifted into position on the base section. Once the wall sections were in place, they were bolted together, and Todd covered the joins with fresh mortar. 

The finished wall looks very much like the walls you can see at Brockinton House and on other buildings in southwest Manitoba, and it beautifully demonstrates both fieldstone construction and the geological variety of this fascinating material. As is the case for some other Museum exhibits, there is no evidence of the incredibly complicated and lengthy development and construction process that allowed this structure to “look like the real thing.” 

By Dr. Graham Young, past Curator of Palaeontology & Geology

As we have worked our way through the pliosaur exhibit project, we have come up against a series of problems that have required novel solutions. About a month ago we carried out a very strange task, and one that none of us had ever had to do before: we needed to move the glyptodont. 

Before I explain how we did this, perhaps I had better backtrack a bit, as you probably have some questions at this point: “What is a glyptodont, anyway? Where did the Museum get its glyptodont and why did you need to move it?” 

Glyptodonts were creatures that lived during the Ice Age, that have been described as “fridge-size armadillos,” although the largest ones could perhaps have been called “armadillos the size of Volkswagen Bugs.” They were heavy, armoured creatures that weighed up to two tonnes. They spent their time lumbering around the forests and plains of South America and southern North America,  eating trees and grasses. Glyptodonts became extinct about 10,000 years ago during the “Quaternary Extinction Event,” at about the same time as giant ground sloths and other large mammals, probably as a result of climate change and hunting by humans. 

Our particular glyptodont is a replica of a fossil that belonged to the genus Glyptodon, and like our ground sloth it came to the Museum by a long and circuitous route. The glyptodont and the ground sloth were among the earliest casts of big vertebrate fossils, produced during the late 19th century by Ward’s Natural Science Establishment in Rochester, New York. Our ground sloth (Megatherium) was supplied to the Redpath Museum in Montreal in time for the opening of that institution in 1882, while the glyptodont joined it in Montreal some years later. 

By the 1960s, the Redpath was renovating, and these immense casts were removed and needed a home. The Manitoba Museum was under construction, so the casts were transferred to us and shipped to Winnipeg. They were assembled when the Earth History Gallery was constructed, and were there in time for the gallery opening in 1973. For the forty-plus years since then, both of these huge and historic casts have stood in place on the platforms that had been constructed for them. 

Now, in 2016, we are renovating that part of the gallery so that we can install our exciting fossil pliosaur, and to make space we have had to move the glyptodont. Since this replica had been in place since long before any of us worked here, we did not have any advance knowledge of how it should be handled, and since it is an irreplaceable artefact dating from  over a century ago, we considered this move with some trepidation. Since it turned out that the glyptodont is also immensely heavy, having been constructed of plaster, wood, and iron in the best 19th century fashion, our trepidation was well placed. 

As has been the case with handling the plesiosaur specimen, our technical staff love this sort of challenge, and Bert Valentin and Sean Workman had come up with solutions in the best “jury rigged” manner. Back when we installed our mineral exhibit, Bert had modified an engine hoist so that we could move our giant amethyst specimen, which weighs close to half a tonne. Now, with a fossil cast that weighs about the same amount (we weren’t able to weigh it, so this is a best guess), Bert re-modified that hoist as a glyptodont-lifter. The following sequence of photographs shows how it went – the process was much more nerve-wracking than it appears here! 

By Dr. Graham Young, past Curator of Palaeontology & Geology

If you think about how Museum paleontologists get fossils, you might guess that we go out and find where the fossils are, extract all of them from the rock and sediment, and return them to the Museum. Certainly that is what we do where fossils are scarce, but in many instances our job really consists of deciding what to leave behind. Our specialists at the Manitoba Museum are called curators, and a curator by definition has to be able to select what is needed for collections and exhibits. 

This fact was really brought home to me in the past couple of weeks, as we revisited sites in Airport Cove, the stretch of shoreline north of the airport at Churchill. Airport Cove covers a large area, with many patches of bedrock spread across the shoreline. These patches of rock allow us to sample many different sedimentary beds from the end of the Ordovician Period and the beginning of the Silurian Period, roughly 445-435 million years ago. 

The rocks in the cove were deposited as sediment in warm tropical seas, so fossils are plentiful in many of them. With such an embarrassment of riches we have to be selective every time we go out in the cove; if I collected every decent fossil, we would need an entire freight train to get them to Winnipeg!  And then, where could we possibly store them? 

As a result of our previous work here, many examples of the “standard” fossils from Airport Cove are already resident in the Museum’s collections, and this time we were looking for very specific and rare things. So we would walk around the cove each day, considering and photographing the more common sorts of fossils. Some of these are old friends, on blocks of stone that I can remember being in the same place ten or fifteen years ago. Others were new to me, but I can hope to see them again if I get back here. And then there are the few fossils that are so good that they must go to the Museum; one of these is shown at the end of this piece. 

If you are ever in the Churchill area and wish to go looking for fossils, please follow all  guidelines on polar bear safety! We had to leave our work area at Airport Cove twice last week as there were bears nearby, and on one occasion a mother and cub walked right through our site very shortly after we got into the truck. 

By Dr. Graham Young, past Curator of Palaeontology & Geology

Those of us who live in Winnipeg know that fossils are never far away. Many Winnipeg structures feature surfaces clad in Tyndall Stone, a fossil-rich dolomitic limestone of Late Ordovician age (about 450 million years old). Tyndall Stone covers public buildings such as the Manitoba Legislative Building and the Winnipeg Art Gallery, and commercial buildings in the downtown core, but it can also be seen in thousands of homes in Winnipeg: in walls, steps, and fireplaces. 

Thus, it is hardly surprising that the Museum and the adjacent Centennial Concert Hall both use Tyndall Stone inside and out. Of course Tyndall Stone fossils are represented in our Earth History Gallery, but if you think about it, it is odd that there are so many more “museum-grade specimens” exposed to the weather on the outside of the building. On the inside, as these photos show, we sometimes cover up beautiful fossils with the detritus of everyday existence: signs, fountains, alarms, and thermostats. In part, this is because the fossils are so abundant that it is hard to avoid them when placing objects, but it may also be that they are so commonplace here that people ignore them and take them for granted. 

Maybe someday we will add interpretative signage to some of the better and more accessible fossils on and in the Museum, but that would be a big project to undertake. In the meantime, here is a sampling of a few of the good ones.