How It Is Preserved
Normally, organic carbon is decayed before it is rotted. Anoxia can prevent decay, but the prevalence of bioturbation associated with body fossils indicates that many BS sites were oxygenated when the fossils were deposited. It seems that the reduced permeability associated with the clay particles that make up the sediment restricted oxygen flow; furthermore, some beds may have been 'sealed' by the deposition of a carbonate cement.
The carbon isn't preserved in its original state, which is often chitin or collagen. Rather, it is kerogenized. This process seems to involve the incorporation of aliphatic lipid molecules.
Read more about this topic: Burgess Shale Type Preservation
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