The Tonian (from , meaning "stretch") is the first geologic period of the Neoproterozoic Era. It lasted from to 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.
via Wikipedia infobox
The Tonian (from , meaning "stretch") is the first geologic period of the Neoproterozoic Era. It lasted from to 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.
== History == The Tonian was defined in 1990 by the New Precambrian time scale as being from 1000 to 850 Mya. The name Tonian comes from , which means the word "stretch", referring to the rifting that broke up Rodinia during this period. The upper definition was then redefined to 720 Mya in 2014 after discoveries that the original 850 Mya for the lower Cryogenian and the first glaciations at 717 Mya did not match. This is temporary until the basal Cryogenian GSSP is chosen.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).