Tonian

The Tonian (from Greek τόνος (tónos), meaning "stretch") is the first geologic period of the Neoproterozoic Era. It lasted from 1000 Mya 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.

Tonian Period 1000–720 million years ago PreꞒ Ꞓ O S D C P T J K Pg N

A map of the world as it appeared during the late Tonian period. (750 ma)

Events of the Tonian Period -1020 — – -1000 — – -980 — – -960 — – -940 — – -920 — – -900 — – -880 — – -860 — – -840 — – -820 — – -800 — – -780 — – -760 — – -740 — – -720 — – -700 — – Tonian Cryogenian Stenian   M P Z N e o p r o t e r o z o i c           * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ← First sponge-like animal? ← Kaigas glaciation?[1] ← Sturtian glaciation ← Sharp drop in Stromatolite Population[2]

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.

Biology

The first large evolutionary radiation of acritarchs occurred during the Tonian.

The first putative metazoans (animal) fossils dated to the late Tonian (c. 800 Mya). A notable example of this is the Otavia antiqua, which has been described as a sponge by its discoverers and numerous other scholars. This dating is consistent with molecular data recovered through genetic studies on modern metazoan species; more recent studies have concluded that the base of the animal phylogenetic tree is in the Tonian.[3]

See also

• Boring Billion – Between 1.8 and 0.8 billion years ago
• Riphean (stage)

References

1. Macdonald, F. A.; Schmitz, M. D.; Crowley, J. L.; Roots, C. F.; Jones, D. S.; Maloof, A. C.; Strauss, J. V.; Cohen, P. A.; Johnston, D. T.; Schrag, D. P. (4 March 2010). "Calibrating the Cryogenian". Science. 327 (5970): 1241–1243. doi:10.1126/science.1183325. PMID 20203045. (Duration and magnitude are enigmatic)
2. 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): 5. doi:10.1073/pnas.1221721110. Retrieved 28 February 2020.
3. Kliman, Richard M. (Apr 14, 2016). Encyclopedia of Evolutionary Biology. Academic Press. p. 251. ISBN 9780128004265.

• "Tonian Period". GeoWhen Database. Archived from the original on May 12, 2006. Retrieved January 5, 2006.
• James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale". Lethaia. 37 (2): 183–199. doi:10.1080/00241160410006492.