Sandilands reflect continent’s long history

Picturesque hills shaped by Lake Agassiz

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Manitoba has its share of places to visit and sights to see, but have you ever wondered about the ancient origins of sites such as the Pembina Valley or Clay Banks Buffalo Jump? In this series, authors Barbara Huck and Doug Whiteway explore the geological, paleontological and archeological history of some of Manitoba’s many attractions in excerpts from their book, In Search of Canada’s Ancient Heartland. Today: Sandilands Provincial Forest.

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Hey there, time traveller!
This article was published 26/09/2020 (799 days ago), so information in it may no longer be current.

Manitoba has its share of places to visit and sights to see, but have you ever wondered about the ancient origins of sites such as the Pembina Valley or Clay Banks Buffalo Jump? In this series, authors Barbara Huck and Doug Whiteway explore the geological, paleontological and archeological history of some of Manitoba’s many attractions in excerpts from their book, In Search of Canada’s Ancient Heartland. Today: Sandilands Provincial Forest.

 

Excerpted with permission from In Search of Canada’s Ancient Heartland, by Barbara Huck and Doug Whiteway, available at independent booksellers and from the publisher, Heartland Associates (hrtland@mts.net)

Bartley Kives / Winnipeg Free Press Files The Sandilands Moraine is among few places where mature red pines can be found on the Canadian Prairies.


 

Today, Sandilands Provincial Forest’s rippling hills and bountiful woodlands are home to a great variety of birds and mammals and, particularly in the south near the Minnesota border, to some of Manitoba’s most majestic trees. Winter and summer, these lovely uplands draw cross-country skiers, hikers, bikers and equestrians.

But there is much more here, for the origins of this moraine are long and complex; in fact, it might be said that Sandilands’ fascinating past is North America’s long history encapsulated. Created by ice and shaped by one of the largest lakes the world has ever known, these picturesque hills also hold remnants of North America’s primeval mountains and its ancient tropical seas.

The region is well named. Like the Belair Moraine, with its Ancient Beach Trail at Grand Beach to the north, this height of land is composed almost exclusively of fine sand and large boulders. The sand is largely grains of golden Ordovician sandstone, part of a layer of sand and shale — the Winnipeg Formation — that overlies the Precambrian Shield in much of central North America, while the boulders are largely pieces of the North American craton, the very foundation of the continent, that were carried here by the huge ice sheet during the last glaciation.

While the Shield dates back into the mists of time, the Winnipeg Formation was laid down some 460 million years ago as warm seawater inundated the ancient continent of Laurentia. Working with a vast store of materials from the sediments that had eroded from Laurentia’s once towering mountains over millions of years, the ocean waters laid down a distinct layer of sandstone and shale.

As time passed, North America’s inland seas capped the Winnipeg Formation with layer upon layer of much harder limestone and dolostone. These layers include what geologists call the Selkirk Member, fossil-rich Tyndall stone that was used to create Canada’s Parliament Buildings in Ottawa, the Canadian Museum of Civilization in Hull, Que., and Manitoba’s Legislative Building. In much of the Interlake, these layers of limestone were very thick, but in some places along what is now the eastern shore of Lake Winnipeg, some of the Ordovician sandstone was close to the surface. It was unearthed by the great continental ice sheets as Earth’s most recent glaciation — the Late Wisconsinan — reached its climax about 18,000 years ago.

Two enormous ice sheets covered Manitoba during the Wisconsinan glaciation — the Keewatin dome from west of Hudson Bay and the Labradorean dome to the east. Flowing south and west along what is now the east side of Lake Winnipeg, the Labradorean dome pulverized the sandstone and incorporated the fine granules of sand. As global temperatures slowly (and rather hesitantly) began to rise, the great sheets of ice began a series of retreats and readvances, melting at their margins where the ice was thinner, often stabilizing for a time and then advancing again southwards. Responding to this melting, the Labradorean dome split into two distinct lobes — the Red River Lobe in the Manitoba Lowlands and the Rainy Lobe in southeastern Manitoba and northwestern Ontario.

Over the next millennia, the two lobes grew and shrank independently, with the Rainy Lobe first moving westward into northwestern Minnesota, before changing direction to head southward over northeastern Minnesota. The Red River Lobe, meanwhile, headed south, eventually combining with the Des Moines lobe to push deep into Iowa. Between these two great lobes, the Belair, Milner Ridge and Sandilands Moraines were formed. Each time the climate warmed and the forward momentum of the great ice sheets halted for a time, sand-laden meltwater poured off the glaciers and huge boulders dropped from the ice.

As the centuries passed, the result was a southeasterly trending chain of hills of fine sand and large rocks, anchored in the south by Sandilands. Ultimately, the snubnosed moraine grew high enough and substantial enough that even when the ice lobes readvanced, they were unable to flow over the ridge.

Then, as the world warmed, the moraine was swallowed for a time by the deep, cold waters of Lake Agassiz. But about 11,000 years ago, the water level had dropped enough to allow Sandilands and its counterparts to the north to poke above the cold waves. For more than a thousand years, what are now forested oases on the edge of southern Manitoba’s eastern Prairie were islands of sand above the ice-cold, storm-tossed water of Lake Agassiz — sort of an arctic version of the semi-tropical sand islands that lie today off Australia’s east coast.

As indicated in the introductory chapters, Lake Agassiz grew and shrank many times over the millennia as meltwater poured in from the north, east and west, or the giant lake drained through one of its many outlets. As it rose and fell, its powerful waves eroded the slopes of the Sandilands Moraine, creating a series of ancient beaches that geologists have used to plot Lake Agassiz’s size and depth at various times. Two of these — the Lower Campbell and Upper Campbell Beaches — and wavecut scarps on the northwestern nose of Sandilands Moraine can be seen quite easily on satellite maps, as well as on the maps created by the Geological Survey of Manitoba.

Today, the moraine is largely forested and among the few places where mature red pine can be found on the Canadian Prairies. Visitors can enjoy the forest in all seasons, thanks to the volunteer efforts of the Sandilands Ski Club, which signs and grooms ski, equestrian and biking or hiking trails, and to Manitoba Conservation, which provides a ranger station and two parking lots, including one at Marchand Wayside Park, which is complete with tables and a covered picnic area.

 

Getting there

Geological Survey of Manitoba This relief map of the Sandilands Moraine clearly shows Lake Agassiz’s Upper and Lower Campbell Beaches, as well as its steep wave-cut cliffs.

From Winnipeg, go south on PTH 59 to PTH 52. Turn east, past Steinbach where PTH 52 turns into PR 210; continue past Marchand to Sandilands Provincial Forest. Parking is available at the Ranger Station and most trails go from there.

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