The Marros Group consists of siliceous mudstones and locally quartz rich sandstones and conglomerates.
See also the Marros Group in the BGS lexicon of named rock units.
The Marros Group is present from Pembrokeshire throughout southern Wales and east of the Bristol Channel.
The maximum height of the top of the Marros is about 400 lm above OD at outcrop in south Wales and is at its deepest in south Wales and to the east of the Bristol Channel, reaching depths of over 2500 m below OD.
Please contact BGS Enquiries for more information.