THE STEPHEN FORMATION OF MARBLE CANYON, KOOTENAY NATIONAL PARK, BRITISH COLUMBIA: A SEDIMENTOLOGICAL AND STRATIGRAPHIC CHARACTERIZATION

The Middle Cambrian basinal Stephen Formation of the southern Canadian Rocky Mountains contains the best-known deposit of soft-bodied fossils on the earth: the Burgess Shale. The Burgess Shale biota is taxonomically diverse and represents the rapid radiation in complex life characteristic of the Cambrian Explosion. A new Burgess Shale-type deposit was discovered within the basinal Stephen Formation in 2012. This new area—Marble Canyon—is located in Kootenay National Park, British Columbia, roughly 40 km southeast of the original Burgess Shale-type deposit at Fossil Ridge and Mt. Stephen in Yoho National Park, British Columbia. Although taxonomic overlap exists between the Fossil Ridge and Mt. Stephen and Marble Canyon fossil assemblages, many species unique to the Marble Canyon area have been discovered. The suite of lithofacies within the basinal Stephen Formation at Marble Canyon is identical to the basinal Stephen Formation at Fossil Ridge, though the stratigraphic arrangement at each area differs. Previous workers have identified either 2 or 10 members within the basinal Stephen Formation at Fossil Ridge and Mt. Stephen. Two members are recognized at Marble Canyon—the Whymper Member and the Marble Canyon Member. Geochemical data confirms the continuity of lithologies between the basinal Stephen Formation of Marble Canyon and the Burgess Shale Formation of Yoho National Park. Additional ⁸⁷Sr/⁸⁶Sr isotope data will be used to determine unit contact ages.