Trilobite zone
Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones. The Olenellus-zone has traditionally marked the top of the Lower Cambrian, and is followed by the Eokochaspis zone.
The last two zones of the Middle Cambrian are the Bathyuriscus–Elrathina-zone (contemporaneous with the Burgess Shale) and the subsequent Bolaspidella-zone (starting at the base of the Drumian stage). These are overlain by the lowermost Upper Cambrian Cedaria-zone.
Alternative zoning names place the Burgess Shale in the Peronopsis bonnerensis-zone, which is underlain by the Oryctocephalus indicus-zone (e.g. Spence Shale) and overlain (perhaps not directly) by the Ptychagnostus punctuosus-zone.
The lower Middle Cambrian Glossopleura-zone (Spence Shale) is above the Albertella-zone.
The Elvinia-zone is upper Cambrian.
| Series | Stage | Trilobite zone | Trilobite GSSP |
|---|---|---|---|
| Furongian | Stage 10 | Saukia-zone (upper part), Eurekia apopsis-zone, Tangshanaspis-Zone, Parakoldinioidia-zone, Symphysurina-zone | Lotagnostus americanus (undecided) |
| Jiangshanian | Ellipsocephaloides-zone, Saukia-zone (lower part) | Agnostotes orientalis | |
| Paibian | ? (?) | Glyptagnostus reticulatus | |
| Cedaria | |||
| Miaolingian | Guzhangian | Bolaspidella ( / Ptychagnostus praecurrens ?? ). | Lejopyge laevigata |
| Drumian | Ptychagnostus atavus | ||
| Wuliuan | Bathyuriscus–Elrathina (?) | Oryctocephalus indicus | |
| Eokochaspis | |||
| Series 2 | Stage 4 | Olenellus | Olenellus or Redlichia (undecided) |
| Stage 3 | |||
| Fallotaspis, Nevadella | First appearance of trilobites (undecided) | ||
| Terreneuvian (Pre-Trilobitic Cambrian) | Stage 2 | ? | |
| Fortunian |