Reversing Rapids

Rocks

The Reversing Rapids are famous for the tidal phenomenon that forces the St. John River to flow backwards as the Bay of Fundy reaches high tide. A much older geological story here involves the collision of ancient continents. The rocks at the Reversing Rapids exhibit one of the most interesting stories in the Stonehammer Geopark. Here you can see the contact of two ancient geologic terranes, and the fault line that marks the boundary between them. The rocks south of the bridge are Cambrian age rocks of the Caledonia Terrane, 542 to 490 million years old. North of the bridge the light gray rocks are Precambrian age from the Brookville Terrane. The Ashburn Formation marble and the Martinon Formation are 750 million to 1.2 billion years old. At the Reversing Rapids we can see the contact of these two ancient continental fragments.

Terrane Contact

The gorge at the Reversing Rapids displays a terrane contact. A terrane is a fragment of the earth’s crust formed on, or broken off from, one piece of the earth’s crust (or tectonic plate) and attached or welded to the crust on another plate. The fragment of crust preserves its own distinctive geologic history, which is different from the crust it has become welded to. In this case the two terranes, Brookville and Caledonia, both originated in the southern hemisphere, but they are 500 million years different in age. Starting in the Cambrian perhaps 540 million years ago these two fragments of crust were sliced off a continental mass centered near the South Pole. As an ocean basin opened behind them, and one closed in front, they drifted northward to collide with ancient North America. Here they are! A line of weakness separates the two terranes and during later crustal movements a fault (Caledonia Fault) developed along the terrane boundary.

Ice Age

About 20,000 years ago the last glacial period reached its maximum. Glaciers covered all of the Maritimes. As the continental glaciers retreated they left a changed landscape. Before the last glaciation the St. John River flowed to the sea through South Bay, past the Irving Nature Park. Glacial moraines damned that outlet. When the river found its new route 15,000 years ago it flowed over the rock ridges at Reversing Rapids to create this gorge. Thousands of years ago a waterfall existed here, but as sea level rose and the riverbed eroded, the waterfall was drowned. The phenomenon of the Reversing Rapids is only about 3,000 years old. A profile of the river bed shows a series of three waterfalls must have existed here starting near the islands at Fallsview Park and ending near the bridges. Just past the islands the river bottom drops to about 25 metres below low water level. It then drops two more times to more than 40 metres below low water level just past the road bridge.

Access:
Access:
Disabled Friendly:
Hours:
Dawn Till Dusk
Location:
Address:
Highway 100, Fallsview Drive
Saint John, New Brunswick
Canada
GPS:
45.2642664, -66.0880366
Phone:

Rockwood Park

Rocks

The park is appropriately named. The rocks found in Rockwood Park are quite diverse. They include Precambrian marble, Precambrian gneiss, Precambrian to Cambrian igneous rocks (granite), tonalite, granodiorite and dacite and Devonian sandstone and conglomerate. Two geologic terranes are found in the park. The Caledonian Terrane includes the McBrien Lake Formation dacite and the Cambrian Saint John Group, found just outside the park. Northwest of the dacite, rocks belong to the Brookville Terrane. The Devonian rocks are a later cover sequence of younger sedimentary rocks.
A major fault called the Caledonia Fault separates the terranes. The main road past the Lily Lake Pavilion follows the fault line.

A Long History

Rockwood Park has had a long history of scientific study and geological exploration. The Natural History Society of New Brunswick examined the geology of the park in the late 1800s. Rock specimens Society members collected from the park are found in the New Brunswick Museum collection. Howes Cave in the Ashburn Formation marble was discovered in the 1860s and described in the Society Bulletin in 1904. Even earlier in the 1800s a graphite mine operated near the outlet of Lily Lake.

Geocaching

Rockwood Park has many trails that allow opportunities to explore the geology on foot, on a mountain bike, or on horseback. Get up-close by rock climbing with a guide. In the winter it is a great place to explore on cross-county skis or snowshoes.

Access:
Access:
Disabled Friendly:
Hours:
Dawn Till Dusk
Location:
Address:
10 Fisher Lake Drive
Saint John, New Brunswick
Canada
GPS:
45.3039657, -66.0594638

Hampton Lighthouse River Centre

Rocks

The rocks near the Hampton Lighthouse River Centre are rarely seen. This part of the Kennebecasis River follows softer rocks of the Carboniferous Mabou Group. The valley is bounded on the south by sandstone and conglomerate of the Kennebecasis Formation and on the north by Silurian volcanic rocks.  The river here meanders along the flat valley and is the land is quite marshy. The looping meanders of a mature river can be seen on the geological map. In this case the bedrock you do not see is controlling the landscape. To the southwest the river turns west along a fault line until it becomes trapped between the Devonian Kennebecasis Formation and the Silurian Bayswater Formation.

Modern Analogues

An interesting geological lesson learned here is that of modern analogues. We can examine the modern environment to help us understand paleoenvironments. To the east of Hampton, Highway 1 passes through impressive outcrops of the Albert Formation. These sedimentary rocks were formed 350 million years ago. Small ripple marks and large scale ripples can be seen along the highway. Fossil logs, fish and trace fossils have been found in the Albert Formation. What kind of environment was this?
If you take a boat ride along the Kennebecasis River at Hampton, look down into the river. It is often shallow enough to see ripples on the bottom, waterlogged logs rolling downriver, fish, and winding trails left by clams and other animals. It looks remarkably like the Albert Formation that geologists believe represents shallow rivers, lakes and swamps from the Early Carboniferous Period.

Floodplains

Low-lying areas along rivers are called floodplains for a reason. Try coming here in April or May. Boating along the narrow stretches of the Kennebecasis River valley is a different experience during flood season. In a kayak or canoe you can paddle through the trees. The geologic map identifies the flat-lying Carboniferous Mabou Group. The river meanders from one side of the valley to the other. Old meander scars are visible on the geologic map or on satellite images. During flood season the entire valley is susceptible to flooding.

Access:
Access:
Disabled Friendly:
Hours:
Dawn Till Dusk
Location:
Address:
1075 Main Street
Hampton, New Brunswick
E5N 6G1 ~ Canada
GPS:
45.5416133, -65.8365364
Phone:

Irving Nature Park

Rocks

The geology of the Irving Nature Park includes both Devonian to Carboniferous bedrock (359 to 346 million years old) exposed on Taylors Island and at Sheldon Point and overlying sand, gravel and clay deposited during the last ice age less than 15,000 years ago. The age of the older volcanic and sedimentary rocks has been hard to determine. 

Although they have many interesting features, this note will focus on the ice age geology of the Irving Nature Park. This is one of the best places in Stonehammer to see this part of the geologic record. The ice age geology is made up of “unconsolidated” sediments. They are not rock yet, they are too young.

 

Climate Change

The end of the ice age was a time of rapid climate change especially during the “Younger Dryas” cold interval. About 11,000 years ago temperatures plummeted about 7˚C in a decade. Sub-arctic insects re-invaded the Maritimes for hundreds of years until temperature warmed again. A peat bog on the hill at Saints Rest Beach records this rapid climate event.

Glaciers

At a time geologists call the “Last Glacial Maximum”, about 20,000 years ago, continental glaciers covered most of North America, including the Maritimes. By 10,000 years ago New Brunswick was probably “ice-free”. As the glaciers retreated they left piles of sand and gravel along their margin. Called “moraines” and “outwash”, these piles of sediment are easily seen on the modern landscape. We often use them as sand and gravel quarries. The quarry on Sand Cove Road above the beach is an example. About 15,000 years ago the front of the glacier stood here at the Irving Nature Park. It is called a tidewater glacier since the glacier ice was up against the ocean. The red clay along the beach cliffs is composed of layers of ocean sediment. Occasionally fossils of snails, clams, sea urchins and starfish can be found in the clay. As the glacier continued to retreat it left a series of moraines where it stood still for a period of time. Looking northwest from the beach you can see Manawagonish Road on the hill. The road is built on the Manawagonish Moraine. This moraine acted as a dam and forced the St. John River to flow through the Reversing Rapids.

Access:
Access:
Disabled Friendly:
Hours:
Location:
West Saint John
Address:
1379 Sand Cove Road
Saint John, New Brunswick
E2L 4M3 ~ Canada
GPS:
45.2257772, -66.1175892

Fundy Trail

Rocks

The rock outcrops along the Fundy Trail Parkway expose both Precambrian to Cambrian rocks near the bridge at Big Salmon River, and Triassic age rocks along the coast to the west. About 400 million years of Earth history can be seen here. The older rocks tell the story of the ancient Iapetus Ocean. In Greek mythology Iapetus was a Titan, and father of Atlas. The modern Atlantic Ocean is named after Atlas.

The Atlantic Ocean

The Atlantic Ocean is a relatively recent geological feature, only about 200 million years old. The rocks at Big Salmon River are 600 million years old! The Atlantic Ocean was created by sea-floor spreading. Molten rock from the Earth’s interior rises to the surface to create new crust. As it rises and cools the new crust expands along volcanic mountain chains on the seafloor. Old crust returns to the Earth’s interior along deep ocean trenches. Seafloor volcanic mountain chains mark the middle of an expanding ocean basin. The rising molten material creates a ‘bubble’ in the crust that eventually breaks (to create volcanoes).
They eventually join to form a long break in the crust where a new ocean is born. One crack fails to join another. The ‘failed rift’ is called an aulacogen. The Bay of Fundy is a ‘failed rift’ created when the Atlantic Ocean was born. Instead of becoming part of a new ocean, it became a ‘rift valley’ that filled with sediment.

Coastal Erosion

Rocks are eroded by the action of water slowly breaking down the layers into smaller pieces. As the rocks are slowly worn down the sand and mud will be washed out into the Bay of Fundy. They will eventually become sedimentary rocks again as part of the recycling of the Earth’s crust. ‘Flower pots’ are a picturesque result of coastal erosion. They are small fragment so the eroding coastline that have withstood the pounding of the sea. They remind us where the coastline once stood. Someday they will succumb to the sea.

Access:
Access:
Mid May (Victoria Day weekend), through mid October (Canadian Thanksgiving weekend) Off-season access to the park is available through our off-season gate located just outside the main entrance for walking, hiking and biking only.
Disabled Friendly:
Yes
Hours:
May 20-Jun 24 9am-5pm
Jun 25-Aug 19 8am-8pm
Aug 20-Sep 5 9am-7pm
Sep 6-Oct 10 9am-5pm
Location:
Address:
Entrance
3 Fundy Trail Parkway
Salmon River, New Brunswick
E5R 1W4 ~ Canada
Office
229 Main Street
St. Martins
E5R 1B7 ~ Canada
GPS:
45.4085942, -65.4314777

Brundage Point River Centre

Rocks

Although the bedrock geology is hard to see at the Brundage Point River Centre it still shapes the landscape all around. The rocks at Brundage Point and across the St. John River on the Kingston Peninsula are mostly Silurian age volcanic rocks, about 435 million years old. They are relatively hard rocks and are responsible for the rolling hills seen in the distance. The hills have been smoothed by glaciers that covered the entire area during the most recent glaciation. The river valley has also been smoothed by glaciers.

The St. John and Kennebecasis river valleys follow the bedrock structure along the Kingston Peninsula. They are also following major fault boundaries separating geologic terranes.

Terrane

A terrane is a fragment of the earth’s crust formed on, or broken off from, one piece of the earth’s crust (or tectonic plate) and attached or welded to the crust on another plate. The fragment of crust preserves its own distinctive geologic history that is different from the crust it has become welded to. They are often referred to as ‘exotic terranes’ since they have come from somewhere else. Some have travelled halfway across the globe. New Brunswick is composed of a series of terranes stacked up against the older core of North America. Each slice has its own geological story and relates to a complex history of how New Brunswick came together. Stonehammer park itself is made of many terranes and has a complicated geologic past. Brundage Point is located on the Kingston Terrane. As the St. John River makes its way to the Bay of Fundy is will cross two more terranes.

Ice Age River

The St. John River flows past Brundage Point on its way to the sea. Fifteen kilometres from here the river passes through the Reversing Rapids gorge and into the Bay of Fundy. The view from here has changed dramatically over the years. 15,000 years ago this valley was completely covered by glaciers. When the glaciers retreated the ocean flooded this valley past Fredericton to create an inland sea. Over thousands of years sea level dropped and the land rebounded as the weight of glacial ice was removed. The connection to the sea was cut-off and a series of waterfalls formed at the Reversing Rapids in Saint John. The St. John River became a large lake.

Sea level has been rising again for thousands of years and the land has slowly subsided. The result has been the flooding of the mouth of the Saint John River again as the sea overtopped the rock ridges at the Reversing Rapids. The ‘reversing’ of the rapids is a relatively recent phenomenon. It has only been about 3,000 years since the rising tides have force the St. John River to flow backwards. The waterfalls have been drowned and the effect of the tide can be seen upriver of Brundage Point.

Access:
Year Round
Access:
Disabled Friendly:
Yes
Hours:
Dawn Till Dusk
Location:
Hwy 177, Grand Bay-Westfield
Address:
4 Ferry Road
Grand Bay-Westfield, New Brunswick
E5K 0A8 ~ Canada
GPS:
45.3476675, -66.2236648
Stonehammer UNESCO Global Geopark