The Avon Group is a stratigraphic unit of Courceyan age (Lower Carboniferous) found in southern Wales and the west of England. It forms part of the Carboniferous Limestone Supergroup.[1] The term replaces the old 'Lower limestone Shale Group' of this region.
| Avon Group | |
|---|---|
| Stratigraphic range: Lower Carboniferous | |
| Type | Group |
| Unit of | Carboniferous Limestone Supergroup |
| Sub-units | Tongwynlais Formation, Castell Coch Limestone Formation, Cwmyniscoy Mudstone Formation, Shirehampton Formation, Jackie Parr Limestone Formation |
| Underlies | Pembroke Limestone Group |
| Overlies | Upper Old Red Sandstone |
| Thickness | 10m to 156m |
| Lithology | |
| Primary | mudstone |
| Other | packstone, grainstone |
| Location | |
| Region | South Wales, Somerset |
| Country | United Kingdom |
| Extent | South Wales, Somerset, Gloucestershire, Shropshire |
| Type section | |
| Named for | Avon Gorge |
It is typically shown undivided on geological maps though three formations are identified on mapping of parts of South wales, namely the Tongwynlais, Castell Coch Limestone and Cwmyniscoy Mudstone formations as defined by Waters and Lawrence (1987). The Shirehampton Formation was recognised in the Bristol area by Barton et al (2002). The entire Avon succession is referred to as the Jackie Parr Limestone Formation (Bridge & Hough (2002)) where it outcrops at Clee Hill and Little Wenlock in Shropshire.[2]
See also
editReferences
edit- ^ "Avon Group". The BGS Lexicon of Named Rock Units. British Geological Survey. Retrieved 29 April 2022.
- ^ Waters, C.N.; Waters, R.A.; Barclay, W.J.; Davies, J.R. (2009). A lithostratigraphical framework for the Carboniferous successions of southern Great Britain (onshore). British Geological Survey. pp. 97–98. ISBN 9780852726266.