Views along the shoreline at Lord Selkirk Provincial Park, on the south coast of Prince Edward Island in Canada, show the red Permian sedimentary rock layers in low cliffs, and as mud beneath the water of the Northumberland Strait. The lush vibrant green of the new season’s vegetation makes a striking contrast to the outcropping red beds.
The whole of Prince Edward Island is underlain by Permian rocks which also extend outwards to New Brunswick and Nova Scotia. They date from around 255 million years ago and were laid down between the Carboniferous period which came before it and the Triassic period which followed it. Towards the end of the Carboniferous, the climate started to warm up and dry out; and this marked the end of the vast wetland forests and swamps that had been so characteristic of the Carboniferous and that are recorded by numerous plant fossils and extensive coal measures.
The plants and trees that continued to grow in the Permian Period were mainly those which were resistant to drought, like conifers, although some plants such as tree ferns persisted in the wetter ares. Remains of these plants have been preserved as fossils in the Permian rocks. The terrestrial red beds of Prince Edward Island have also preserved the bones of vertebrates, reptiles, that were washed down rivers in monsoon flash floods and became buried in pebbles and debris. At Point Prim, very close to Lord Selkirk Provincial Park, trace fossils of one of these mammal-like reptiles has been found. We were not lucky enough to find fossils of any kind while we were there as our visit was so fleeting.
Stephanian to late Early Permian rocks occur in and under PEI. The fields, so famous for their potato crops, are a distinctive red colour, indicating the rock type from which the soil is derived. The rocks themselves are best seen outcropping along the coast – in fact one of the first things you notice as you cross the Confederation Bridge to get to the island is the continuous thin red rocky line along the miles of southern shore.
The Permian strata on PEI are divided into different phases, and those shown in the photographs here, from Lord Selkirk Park near Point Prim, belong to the Wood islands Member, which together with the Malpeque Member to its west, comprise the relatively recently-designated Hillsborough River Formation, that belongs to the Northumberland Strait Supergroup. The rocks are made up of conglomerates, sandstones, and mudstones.
van de Poll, H. W., 1989, Lithostratigraphy of Prince Edward Island redbeds, Atlantic Geology, 25, 23-35.
Atlantic Geoscience Society, 2001, The Last Billion Years: A Geological History of the Maritime Provinces of Canada, Nimbus Publishing, ISBN1-55 109-351-0, Atlantic Geoscience Society Special Publication No 15.