Cambrian (geology): Difference between revisions
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==Boundries== | ==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).<ref> All ICS chronological data are given with boundaries of plus or minus millions of years.</ref> 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) | 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).<ref> All ICS chronological data are given with boundaries of plus or minus millions of years.</ref> The lower boundry<ref>At the upper most boundary of the Ediacaran system/period in the Neoproterozoic Erathem/Era in the Proterozoic Eonothem/Era of the Precambrian</ref> 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) | *Early Cambrian (542 - 513 mya) | ||
*Middle Cambrian (513 - 501 mya) | *Middle Cambrian (513 - 501 mya) | ||
Revision as of 20:10, 22 April 2007
The Cambrian is both a system of strata and a period of time. The name refers to a chronostatrigraphic or a geochronological unit 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[3] 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. [4] The earliest undefined series (unamed) encompasses the as yet unamed Stage 1 and Stage 2 (earliest to latest). Series 2 extends from 521 mya to 510 mya with two stages. Series 3 (from 510 to 501 mya) is composed of Stage 5, the Drumian Stage (or Age). and Stage 7. The final and last series to be created in the Cambrian, the Furongian, encompasses the Paibian Stage, Stage 9 and Stage 10 [5][6]
| System/Period | Series/Epoch | Stage/Age | Span in millions of years ago |
|---|---|---|---|
| Cambrian | Furongian | ||
| Unnamed | |||
| 492 to 488.3 mya | |||
| 496 to 492 mya | |||
| Unnamed | |||
| Paibian | |||
| 501 to 496 mya |
| System/Period | Series/Epoch | Stage/Age | Span in millions of years ago |
|---|---|---|---|
| Cambrian | Series 3 | ||
| Stage 7 | |||
| 503 to 501 mya | |||
| 506 to 503 mya | |||
| Drumian | |||
| Stage 5 | |||
| 510 to 506 mya |
| System/Period | Series/Epoch | Stage/Age | Span in millions of years ago |
|---|---|---|---|
| Cambrian | Series 2 | ||
| Stage 4 | |||
| 517 to 510 mya | |||
| 521 to 517 mya | |||
| Stage 3 |
| System/Period | Series/Epoch | Stage/Age | Span in millions of years ago |
|---|---|---|---|
| Cambrian | Series 1 | ||
| Stage 2 | |||
| 534.6 to 531 mya | |||
| 542 to 534.6 mya | |||
| Stage 1 |
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). Subcommission on Neoproterozoic 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.
- ↑ At the upper most boundary of the Ediacaran system/period in the Neoproterozoic Erathem/Era in the Proterozoic Eonothem/Era of the Precambrian
- ↑ 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).