a stratum of sedimentary rock exposed in the Rocky Mountains in British Columbia, Canada. The bed, dated to the Cambrian period (about 540 million years ago), is rich in well-preserved fossils of early marine invertebrates, many of which represent evolutionary lineages unknown in later times.
named after the Burgess Pass, British Columbia, where the shale outcrops
Burgess Shale in other Oxford dictionaries
Definition of Burgess Shale in the US English dictionary