The Tortonian roughly overlaps with the regional Pannonian Stage of the Paratethys timescale of Central Europe.
The base of the Tortonian Stage is at the last common appearance of calcareous nanoplankton Discoaster kugleri and planktonic foram Globigerinoides subquadratus.
[6] The top of the Tortonian (the base of the Messinian) is at the first appearance of the planktonic foram species Globorotalia conomiozea and is stratigraphically in the middle of magnetic chronozone C3Br.1r.
In 2020, geologists reported two newly-identified supervolcano eruptions associated with the Yellowstone hotspot track, including the region's largest and most cataclysmic event – the Grey's Landing super-eruption – which had a volume of at least 2,800 cubic kilometres (670 cubic miles) and occurred around 8.72 Ma.
[7][8] Around 10 Ma, the inflow of North Atlantic Deep Water (NADW) into the Indian Ocean increased significantly.