© UNESCO/Walley Hayes
The Joggins cliffs are the Galápagos of the Carboniferous period.

Two metre long “millipedes” and thirty metre high “scale trees” once inhabited the now ghostly Joggins forest, on the western coast of Nova Scotia, Canada. A geological wonder, the Joggins Fossil Cliffs have been added to the World Heritage List.

Fossilized skeletons of amphibians and reptiles inside stumps of fossilized trees preserved in their upright growth position for 300 million years: that’s what the Scotsman Charles Lyell and the Nova Scotian William Dawson found on the cliffs of Nova Scotia, eastern Canada, in the middle of the 19th century. Since this extraordinary adventure of the founding father of modern geology and the most outstanding Canadian geologist of the 19th century, the Joggins Fossil Cliffs have attracted geologists, studentsand other people of all ages.

These cliffs are not fossilized cliffs per se. They are made of sedimentary rocks containing fossils of plants and animals that existed when the sediments were deposited by flooding rivers, during the latter geological Carboniferous period.

The twenty to thirty metre high cliffs are made of numerous sloping layers of Carboniferous sedimentary rocks. They are covered by a ten to twelve metre thick horizontal deposit of Till or “Boulder Clay,” left about thirteen thousand years ago during the melting of the thick sheet of ice that blanketed the area during the last Ice Age.

The cliffs are exposed on the shore of the Chignecto Bay near the head of the Bay of Fundy, to the North East and South West of the small town of Joggins. The late Carboniferous strata slope down to the south at about twenty degrees from the horizontal. In places, the originally horizontal sediment layers are cut by river channels that migrated to different positions while meandering over their floodplains. Later flooding deposited new sediment layers in the channels.

The Carboniferous sedimentary rocks and their contained fossils are all of non-marine, terrestrial origin, and provide many clues regarding the late Carboniferous environment and climate. All the clues indicate the sedimentation took place under a tropical climate, on a portion of the crust located in the Tropics near the Earth’s equator.

Since then, ocean-floor spreading (Continental Drift) has made this part of the crust move northwards to its present position, about half- way between the Equator and the North Pole.

Perhaps the most remarkable animal that existed in the jungle-like forests of Joggins during the Coal Age was “Arthropleura” – a two metre long arthropod similar to an enormous millipede or a sowbug, which lived on the rotting vegetation of the forest floor. Large slabs bearing this beast's distinctive footprints were found in 1964 in a huge rock fall near Lower Cove, at the northern end of the cliff section. The footprints, recovered in 1966, were moulded into a polyester-resin and fibreglass cast that was on display at Mount Allison University in Sackville (New Brunswick) until 1999, and is now at the Fundy Geological Museum in Parrsboro, Nova Scotia. A large piece of the rock bearing the original trackway is on display at the new Joggins Fossil Cliffs Interpretive Centre.

No actual specimen of the animal itself has been found at Joggins, but its tracks are abundant and it must have existed there in large numbers. Similar trackways occur in other areas of the Upper Carboniferous rocks in Nova Scotia, and also on the other side of the Atlantic Ocean in western Scotland, on the Island of Arran in the Firth of Clyde.

Besides actual land-dwelling creatures such as “Arthropleura”, fossils of aquatic animals living in the rivers and lakes of the area and rare examples of airborne, flying insects, such as large dragonflies, have been found.

The trees in this equatorial jungle were enormous “Scale Trees” related to present-day Club Mosses or Lycopods. Their bark was covered by leaf scars that looked similar to the scales of fish or reptiles, and whose pattern varied depending on the type of tree. A diamond pattern is usually characteristic of “Lepidodendron” whereas “Sigillaria” is characterized by parallel vertical rows of scars on the trunk. “Lepidodendron” and “Sigillaria” were the most abundant trees in the ancient Joggins forests.

These trees were gigantic: the fossilized trunks could reach one metre in diameter and be thirty metres high. Their roots, called Stigmaria, are sediment-filled cylindrical fossils spreading out from the bases of the stumps. They are found in a layer of fossil soil called seat-earth or underclay, upon which the trees used to grow. Such layers were usually located below coal seams, which resulted from the combination of tree remains, rotten vegetation and peat that accumulated on the forest floor and were compressed by successive sediment layers and forests.

The boggy undergrowth of the forests abounded in Calamites, a plant species similar to present-day Horsetails or Equisetums whose fossilized stems, occasionally with needle-like leaves still attached, are often found in the area.

If you want a little souvenir, the beach and foreshore of Joggins are full of sandstone casts of Calamites and Stigmaria. However, be careful! The site is a protected area where fossils cannot be extracted from the cliffs or foreshore reefs without a special permit.

Laing Ferguson, Mount Allison University, Sackville (New Brunswick, Canada).

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Photo 2: © UNESCO/Walley Hayes
The Joggins cliffs have attracted visitors since they were discovered.

Photo 3: © UNESCO/Walley Hayes
Fossilized tree.