This picture with fossil ridge in the back ground, is where the Walcott Fossil Quarry is located. As you will read below, it is a great example of shaly rocks in the lower portion and cleaner carbonates above.
After the deposition of the Gog Group, as discussed in Part 1, the rest of the Cambrian saw several cycles of sea level rise and fall. With a rise in sea level, the shoreline was pushed back several hundred miles over the low-lying continent, to what is now central Canada. With reduced sediment input from erosion, limestone deposition dominated the rest of the Cambrian. A shallow carbonate shelf, similar to today’s Bahama Banks, covered Alberta and most of Saskatchewan to the east. Mudstone continued to be deposited in the deep ocean (present-day British Columbia), and at times of high sea level was deposited over the shelf as well.
Alternating mudstone deposited in deep ocean conditions and shallow-water limestone comprise of the Cambrian sedimentary formations of eastern Yoho National Park. The formations are characterized by cycles of deposition which alternated between shaly rocks in the lower portion and cleaner carbonates above. Starting at the base, we have the Mt. Whyte-Cathedral, the Stephen-Eldon, and the lower Pika-upper Pika cycles. During carbonate deposition, algae were important sediment contributors and binders near the seaward edge. Behind the algal rim, carbonate mudstones deposited beyond the influence of tides are the main rock type.
The break between deep and shallow water environments repeatedly re-developed in the same place throughout geological time and this edge of the shallow water rim of the Cambrian North America is referred to as the Kicking Horse Rim.
Revised for web format from “A Geoscience Guide to the Burgess Shale” by Murray Coppold and Wayne Powell, © The Burgess Shale Geoscience Foundation. To purchase this book, please go to: the Yoho National Park Visitors Centre, Alpine Book Peddlers, Amazon.ca, or Amazon.com