Stephen Formation

The Stephen Formation is a Middle Cambrian rock unit in the Canadian Rockies of British Columbia and Alberta, formed about 513 to 497 million years ago from shale, thin-bedded limestone, and siltstone along a low-latitude continental margin. Best known for containing the Burgess Shale biota, it preserves one of the world’s most important records of early animal life. Its depositional setting included the Cathedral escarpment, which created shallower and deeper water sequences. Fossil-bearing mudstones laid down around 505 million years ago below wave base helped preserve soft-bodied organisms, making sites such as Walcott Quarry especially important to understanding Cambrian marine ecosystems and early animal diversification.

Alberta · Canada