Often referred to as the ‘Old Red Sandstone’ the Devonian Period is usually divided into three parts. It lasted from 416 to 359 million years ago.
In fact the ‘ORS’, as it is sometimes referred to, is an informal name for the rocks of the period in Wales and much of the UK but it also covers some of the youngest rocks of the preceding period – the Silurian – so ‘Devonian’ and ‘Old Red Sandstone’ are not exactly equivalent to each other.
The Devonian Period
This period extended over 57 million years. It is divided into three series/epochs which are further subdivided into various stages/ages. Only those stages in bold are represented in the rocks of Fforest Fawr Geopark.
- Upper Devonian epoch (385Ma – 359Ma)
- Famennian stage (374Ma – 359Ma)
- Frasnian stage (385Ma – 374Ma)
- Middle Devonian epoch (397.5Ma – 385Ma)
- Givetian stage (392Ma – 385Ma)
- Eifelian stage (397.5Ma – 392Ma)
- Lower Devonian epoch (416Ma – 397.5Ma)
- Emsian stage (407Ma – 397.5Ma)
- Pragian stage (411Ma – 407Ma)
- Lochkovian stage (416Ma – 411Ma)
Ma = million years (ago)