Avon Group

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

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.

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

• List of types of limestone

References

1. "Avon Group". The BGS Lexicon of Named Rock Units. British Geological Survey. Retrieved 29 April 2022.
2. 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.