Biostratigraphy
The Visean contains four conodont biozones:
- Lochriea nodosa Zone
- Lochriea mononodosa Zone
- Gnathodus bilineatus Zone
- Gnathodus texanus Zone
In British stratigraphy, the Visean is subdivided into five substages. These are from bottom to top: Chadian (the lower part of this substage falls in the Tournaisian), Arundian, Holkerian, Asbian and Brigantian.
Read more about this topic: Viséan
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