Cambrian (geology)
The Cambrian is both a system of strata and a period of time. The name refers to a chronostatrigraphic or a geochronological units of geological measure. The Cambrian is roughly the period between 543 to 490 million years ago in the Paleozoic Era of the Phanerozoic Eon. It encompasses four chronostatrigraphic series and ten epochs and correspondingly, four geochronological stages and ten ages.
| Erathem/Era | System/Period | Series/Epoch | Stage/Age |
|---|---|---|---|
| Paleozoic | Cambrian | Furongian | Unnamed |
| Unnamed | |||
| Paibian | |||
| Unnamed | Unnamed | ||
| Drumian | |||
| Unnamed | |||
| Unnamed | Unnamed | ||
| Unnamed | |||
| Unnamed | Unnamed | ||
| Unnamed |
The name is derived from Cambria, the Roman word for Wales, the area where the rocks of the Cambrian was first studied.[1]
Boundries
The Cambrian is geochronolocally the period from 542 million years ago (mya) with an error factor (plus or minus 1.0 mya) to 488.3 (plus or minus 1.7 mya).[2] The lower boundry is characterised by trace fossils, the lowest occurrence of Treptichnus (Phycodes) pedum and a near base of negative carbon-isotope excursion. The end or upper boundry is characterised by Conodont fossils, and the lowest occurrence of Iapetognathus fluctivagus; just above the base of Cordylodus lindstromi conodont Zone, and just below lowest occurrence of planktonic graptolites. Historically it was subdivided into three epochs (no longer recognized by the ICS)
- Early Cambrian (542 - 513 mya)
- Middle Cambrian (513 - 501 mya)
- Late Cambrian (501 - 488.3 mya)
Currently the Furongian Series (or Epoch) and the Paibian and Drumian Stages (or Ages) are defined and designated by name. [3] The earliest undefined series (unamed) encompasses the as yet unamed Stage 1 and Stage 2 (earliest to latest). Stage 1 extends from 542 mya to 534.6 mya, the Stage 2 extends from 534 .6 mya to 521.0 mya. Series 2 extends from 521 mya to 510 mya with two stages: Stage 3 encompasses the period 521 to 517 mya and Stage 4, 517 to 510 mya. Series 3 (from 510 to 501 mya) is composed of Stage 5 (510 to 506.5 mya), the Drumian Stage (or Age) from from 506.5 to 503 mya). and Stage 7 from 503 to 501 mya. The fnal and oldest series, the Furongian encompases the Paibian Stage (501 to 496 mya), Stage 9 (496 to 492 mya) and Stage 10 (492 to 488.3 mya)[4][5]
Sources
Proposed Global Standard Stratotype-Section and Point for the Paibian Stage and Furongian Series (Upper Cambrian) International Subcommission on Cambrian Stratigraphy, International Commission on Stratigraphy (ICS), International Union of Geological Sciences (IUGS).
References
- ↑ Glossary Illinois State Geological Survey
- ↑ All ICS chronological data are given with boundaries of plus or minus millions of years.
- ↑ Note: All other series and stages are as yet unmamed and referred to simply as "Series" or "Stage", by the ICS.
- ↑ Cambrian Period GeoWhen
- ↑ International Stratigraphic Chart International Commission on Stratigraphy (ICS), International Union of Geological Sciences (IUGS).