The Campbellton sequence of probable Cambrian and early Ordovican age lies south of the Loon Bay batholith, which intrudes the Dunnage Melange on the north. The Loon Harbour Formation at the base of the sequence consists of hundreds or thousands of meters of volcanic rocks. The succeeding Luscombe Formation, 300 m thick, consists of siliceous argillite with 50 m of manganiferous argillite near its base. The succeeding Riding Island Graywacke is 1,000 m thick. The origin of the sequence is compatible with the hypothesis that the ocean floor of the Protacadic. Ocean was subducted in the Dunnage Melange.