The base of the Norian stage is set at ~228 Ma on the new chronstratigraphy chart of the International Commission on Stratigraphy. Still needs further support and eventially a golden spike, but this is the first time the ICS has used the long Norian hypothesis on its published chart.
You can download the latest timescale from here:
End of the semester student blues
1 day ago in The Phytophactor