Only a very small percentage of exposed Cambrian rocks contain fossils from the early Cambrian, such as those found in the Burgess Shales.
Kudos for the link.
I believe, however, that the Burgess Shale is actually middle Cambrian (per Wikipedia- Cambrian=541 to 485.4 mya (million years ago); Burgess Shale=508 mya; I also seem to recall your cite site saying the Burgess was 40 million years into the Cambrian).
Anyway, this makes me wonder what the fossil record is for the 541 to 508 mya period. Too tired and/or lazy to do the research myself.