NEW BURGESS SHALE-TYPE LOCALITY IN THE UPPER STEPHEN FORMATION, KOOTENAY NATIONAL PARK, BRITISH COLUMBIA: STRATIGRAPHIC AND PALEOENVIRONMENTAL SETTING

A new Burgess Shale-type locality in the Middle Cambrian Stephen Formation was excavated in August 2008 by a team organized by the Royal Ontario Museum. This locality lies in Kootenay National Park, approximately 40 km SE of Walcott's Quarry in the “Burgess Shale” locality of the Stephen Formation near Field, B.C. Regionally, the Stephen Formation has two different expressions, termed the “thick” and “thin” Stephen (Aitken, 1997). Respectively, these have been interpreted to represent deposition on a drowned carbonate platform and in an adjacent basin, which was separated from the platform by a submarine escarpment. Whereas the Walcott Quarry occurs in the “thick” Stephen Formation, directly adjacent to the escarpment, the new Burgess Shale-type locality occurs in the “thin” Stephen Formation, deposited either above an escarpment which has no local expression, or on a ramp where no escarpment was present. The sediments which preserve the exceptional biotas at the Kootenay locality are similar to those of the Burgess Shale in cm-to micron-scale attributes, however, the stratigraphic and paleoenvironmental setting of the two localities is different. The “thick” Stephen Formation is approximately 300 m in thickness and is shale dominated in the Field area, whereas the Stephen Formation at the Kootenay locality is 32.5 m thick, and is comprised of six shale – wackestone parasequences, 1.5 – 15 m in thickness. Here, the Stephen Formation is similar in thickness and lithology to other “thin” Stephen sections described from the region, but differs in that no evidence of grading, scour, or cross-bedding is present, indicating that the entire Stephen there was deposited below storm wave base. The fossil-bearing interval occurs higher in the Stephen Formation than the “Burgess Shale”. The locality occupies a stratigraphic and paleoenvironmental setting that is more similar to other Burgess Shale-type deposits worldwide than to that of the original locality.