Piacenzian - Zanclean boundry
The latest GSA time scale shows that 2.6 break:
GSA 2009 time scale - PDF
No doubt the time scale will continue to change as our understanding grows. There has been heated debate over just about every date and every name on this chart. One of the biggest problems, early on, was combining the European system with the one from North America. And, as you can see from the referencing page,GSA Time Scale page discussions continue...