The Tonian (from Greek "tonas", "stretch") is the first
geologicperiod in the NeoproterozoicEra and lasted from 1000 Ma to 850 Ma (million years ago). Instead of being based on stratigraphy, these dates are defined by the ICS based on radiometric chronometry.
Events leading to the breakup of
supercontinent Rodiniastarted in this period.
The first radiation of
acritarchs occurred during the Tonian.
*cite web | title=Tonian Period | work=GeoWhen Database | url=http://www.stratigraphy.org/geowhen/stages/Tonian.html | accessmonthday=January 5 | accessyear=2006
*cite journal | author=James G. Ogg | title=Status on Divisions of the International Geologic Time Scale | journal=Lethaia | year=2004 | volume=37 | issue= | pages=183–199 | url=http://www.stratigraphy.org/precambrian/Ogg_2003.pdf | doi=10.1080/00241160410006492
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