Burgess Shale

Definition and stakes

Various,  Proceedings of the United States National Museum (1930)

“ The marvellous preservation of such a host of species in the Burgess shale gives that fauna a definiteness that is scarcely equaled by any other in the entire geologic column, even though its exact stratigraphic position in the Middle Cambrian may not yet be precisely fixed. The Burgess shale has usually been regarded as the exact equivalent of the Ogygopsis shale member of the Stephen formation which like this bed outcrops in only one restricted area—to the south across the Kicking Horse Valley. ”
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Portrait of Charles Doolittle Walcott Charles Doolittle Walcott,  Cambrian Geology and Paleontology (1914)

“ The compact, smooth, exceedingly fine-grained siliceous Burgess shale was deposited from relatively quiet, muddy water. At intervals this condition must have continued for some time as layers of the shale several inches in thickness have the crustaceans distributed irregularly through them. Where the shale is in thin layers with distinct lamination and bedding surfaces the fossils are more abundant but less perfectly preserved. ”
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Portrait of Charles Doolittle Walcott Charles Doolittle Walcott,  Cambrian Geology and Paleontology (1914)

“ Owing to the Burgess shale member of the Stephen formation being overlain and underlain by massive limestones it is very frequently metamorphosed and cleaved into schists or soft calcareous or siliceous slates.
MODE OF OCCURRENCE
With the exception of Marrella splendens and Hymenocaris perfecta, Agnostus, and Microdiscus, the fossils are irregularly distributed and of relatively rare occurrence. They are pressed flat even in layers where there are no visible traces of lamination of the rock.
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