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Appalachians and the Age of Fishes

Colour image of globe showing changing position of continentsThe Devonian Period is called ‘The Ages of Fishes’ and the Devonian story in New Brunswick includes some great fish tales. By the middle Devonian Period the crust of the Rheic Ocean was subducted beneath the Kingston Arc resulting in a further mountain building episode as the supercontinent Pangea came together. The Iapetus and Rheic Oceans had closed and the Appalachian Mountain range dominated the landscape. The weathering of the mountains covered the landscape with reddish non-marine sediments familiar to people in the Maritimes of Canada and in Europe. The new continent of Euramerica is sometimes called the ‘Old Red Sandstone’ continent. In New Brunswick we see the red sediments in the southeast near St. Andrews, near Saint John, and along the southern part of the province toward Moncton and Memramcook.

Appalachian Mountains built during the final stages of ocean closure and plate cThe final collision and subduction of the Rheic Ocean created granitic magma that rose toward the surface forming the core of the Appalachians. Granitic plutons and rhyolitic volcanoes form a spine across the province from the southwest to northeast creating some of the province’s most prominent landscape features like Mount Carleton and Sugarloaf. This tectonic activity created interesting mineral deposits. Geologic features like the Mount Pleasant caldera, a collapsed volcano, has some of the world’s richest concentrations of rare elements like indium.

Plants and animals were firmly established on land by the Devonian Period. The evolution of land plants continued in the Devonian when plants developed stems and roots. In the early Devonian land plants grew along freshwater shorelines and estuaries. New Brunswick has some of the world’s best fossils of early land plants. Trees did not appear until later in the Devonian so the early landscape had a green fringe along water margins, but was barren otherwise. In the early Devonian animals began to populate the landscape too. Arthropods were among the first animals to invade the land and New Brunswick rocks contain the oldest land animal fossils in North America. Northern New Brunswick preserves an excellent record of early Devonian fish including cephalaspids, sharks, acanthodians, and placoderms.