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Tonian
| Tonian | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
.png) A map of Earth as it appeared during the late Tonian, c. 750 Ma | |||||||||||||||
| Chronology | |||||||||||||||
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| Etymology | |||||||||||||||
| Name formality | Formal | ||||||||||||||
| Usage information | |||||||||||||||
| Celestial body | Earth | ||||||||||||||
| Regional usage | Global (ICS) | ||||||||||||||
| Time scale(s) used | ICS Time Scale | ||||||||||||||
| Definition | |||||||||||||||
| Chronological unit | Period | ||||||||||||||
| Stratigraphic unit | System | ||||||||||||||
| Time span formality | Formal | ||||||||||||||
| Lower boundary definition | Defined chronometrically | ||||||||||||||
| Lower GSSA ratified | 1991[3] | ||||||||||||||
| Upper boundary definition | Redefined chronometrically with an interim calibrated age of c. 720 Ma. GSSP is in progress.[4] (Previously defined chronometrically as 850 Ma)[3] | ||||||||||||||
| Upper boundary definition candidates | The first appearance of widespread glaciation.[5] | ||||||||||||||
| Upper boundary GSSP candidate section(s) | To be determined | ||||||||||||||
The Tonian (from Ancient Greek: τόνος, romanized: tónos, meaning "stretch") is the first geologic period of the Neoproterozoic Era. It lasted from 1000 to 720 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined by the ICS based on radiometric chronometry. The Tonian is preceded by the Stenian Period of the Mesoproterozoic Era and followed by the Cryogenian.
Rifting leading to the breakup of supercontinent Rodinia, which had formed in the mid-Stenian, occurred during this period, starting from 900 to 850 Mya.
- ^ Brain, C. K.; Prave, A. R.; Hoffmann, K. H.; Fallik, A. E.; Herd D. A.; Sturrock, C.; Young, I.; Condon, D. J.; Allison, S. G. (2012). "The first animals: ca. 760-million-year-old sponge-like fossils from Namibia". S. Afr. J. Sci. 108 (8): 1–8. doi:10.4102/sajs.v108i1/2.658.
- ^ Bernhard, Joan (11 June 2013). "Insights into foraminiferal influences on microfabrics of microbialites at Highborne Cay, Bahamas". Proceedings of the National Academy of Sciences of the United States of America. 110 (24): 9830–9834. Bibcode:2013PNAS..110.9830B. doi:10.1073/pnas.1221721110. PMC 3683713. PMID 23716649.
- ^ a b Plumb, K. A. (June 1, 1991). "New Precambrian time scale". Episodes. 14 (2): 139–140. doi:10.18814/epiiugs/1991/v14i2/005.
- ^ Shields, Graham A.; Halversonb, Galen P.; Porter, Susannah M. (2018). "Descent into the Cryogenian". Precambrian Research. 319: 1–5. Bibcode:2018PreR..319....1S. doi:10.1016/j.precamres.2018.08.015.
- ^ Shields-Zhou, Graham A.; Porter, Susannah; Halverson, Galen P. (2016). "A new rock-based definition for the Cryogenian Period (circa 720 – 635 Ma)". Episodes. 39 (1): 3–8. doi:10.18814/epiiugs/2016/v39i1/89231. ISSN 0705-3797.
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