Hannah Caine Drawings

by Hannah Caine

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Sanctacaris image

Burgess Shale Gallery

The Burgess Shale, discovered by Charles Doolittle, contains a diverse range of animals. It is located in British Columbia's, Yoho National Park, in the Canadian Rocky Mountains. The fossil bearing shales are found in a 150 m high and 2 m thick unit, called the Stephen Formation which consists of Walcott and Raymond's quarry. These strata were formed 520 million years ago during the Cambrian Period.

The preservation of the soft bodied fauna is extraordinary. Usually the soft parts decay away leaving no fossil evidence of the animal's existence. The Burgess strata, and their constituent fauna, were deposited at the base of an algal reef in a deep-water basin. Unstable mud and turbidity currents caused periodic mud slumps. These transported the organisms down the sloping banks, to be deposited into anoxic basin waters. These conditions allowed the soft body parts to be preserved as the decay rate was slow and there were no scavengers or predators. Compacted by overlying mud, the fauna is preserved as thin carbon films in graded units consisting of fine mud layers.

During the Mesozoic era the Stephen Formation, including the Burgess Shale was transported along a thrust fault to the present location. This contributed to the extraordinary preservation by allowing protection from heat and pressures of nearby tectonic activities.



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