Mount Carleton is the highest elevation in the Canadian province of New Brunswick. Mount Carleton is a monadnock, an erosional remnant of resistant ingneous rocks that remained after an ancient Mesozoic peneplain surface was uplifted in the Cenozoic to form a plateau. Erosion from glaciers, water, wind has eroded the mountains for hundreds of millions of years. The mountain consists of 400 million-year-old rhyolitic and basaltic volcanics. The underlying rocks of Mount Carleton are part of the Gaspé Belt.