Viséan

The Viséan is a stage in the geologic timescale, and a subdivision of the Mississippian subperiod (also known as the Lower Carboniferous). It is preceded by the Tournaisian and followed by the Serpukhovian. The Viséan stage spanned approximately 13.3 million years, from 346.7 ± 0.4 million years ago (Ma) to 333.4 ± 1.0 Ma.

The name Viséan derives from the city of Visé in Belgium, where rocks of this age are found.

During the Viséan, marine environments were widespread, and extensive limestone deposits formed. The period is marked by significant diversification of marine life, including foraminifera, corals, and brachiopods. Coal swamps also began to develop.

The Viséan is often subdivided into smaller substages or biozones based on characteristic fossil assemblages. These subdivisions can vary regionally. In British stratigraphy, the Viséan is divided into several stages: Chadian, Arundian, Holkerian, and Asbian.