The Geology of the Burgess Shale (Part 2): What Rocks Tell Us About Life

After the deposition of the Gog Group, as discussed in the Burgess Shale Geology 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. This resulted in the ocean inundating many hundreds of kilometers of land to the east of where the Burgess Shale is located. A shallow carbonate shelf, similar to today’s Bahama Banks, covered Alberta and most of Saskatchewan to the east of the Burges Shale. 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.

 

The Cambrian sedimentary formations of Yoho National Park consist of mudstone, deposited in deep ocean conditions, and limestone deposited in shallower-water. These formations are characterized by cycles of deposition which alternated between mudstone rocks in the lower portion and carbonates above. Starting at the base, we have the Mount 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.