Tortonian

The Tortonian is a stage of the Miocene epoch in the international geologic timescale. It spans roughly 11.63 to 7.246 million years ago and is part of the Late Miocene. The Tortonian follows the Burdigalian and precedes the Messinian in the standard astronomical and stratigraphic framework used by geologists around the world.

The name Tortonian is derived from a locality in Italy where rocks of this age were studied, in line with the common practice of naming stages after places. The term is used in both marine and continental stratigraphy to correlate sedimentary sequences deposited during this interval across different regions.

In global stratigraphy, the Tortonian provides a common reference for dating and correlating rocks and fossil assemblages. Regional schemes often subdivide the Tortonian into lower and upper subunits to reflect regional geological differences and to accommodate finer correlations among sites.

Paleoenvironments during the Tortonian were varied across regions. The stage records continued global cooling and diversification of Miocene faunas and floras, with marine sediments preserving a diverse assemblage of foraminifera, mollusks, and other organisms, while terrestrial sediments often show the expansion of more open-habitat ecosystems in certain areas.

Subdivisions commonly recognized in regional charts include the lower Tortonian and upper Tortonian, which help describe chronological and environmental changes within the broader Tortonian interval. The Tortonian remains a key interval for understanding late Miocene tectonics, climate evolution, and biogeographic shifts that set the stage for the subsequent Messinian events.