The Stephen Formation is a middle Cambrian unit exposed in the Canadian Rockies of British Columbia. It is famous for the exceptional preservation of soft-bodied fossils: the Burgess Shale biota. The formation overlies the Cathedral Escarpment, a submarine cliff; consequently it is divided into two quite separate parts, the 'thin' sequence deposited in the shallower waters atop the escarpment, and the 'thick' sequence deposited in the deeper waters beyond the cliff. Because the 'thick' Stephen Formation represents a distinct lithofacies, some authors suggest it warrants its own name, and dub it the Burgess Shale Formation.