Computer Code: |
GDGP |
Preferred Map Code: |
notEntered |
Status Code: |
Index Level |
Age range: |
Wenlock Epoch (SW)
— Ludlow Epoch (SU) |
Lithological Description: |
[Obsolete] Slates, slates with thin silty sandstone-bands, alternating bands of cleaved mudstone and uncleaved laminated siltstone, fairly thinly bedded shales and perfectly cleaved silty mudstones. |
Definition of Lower Boundary: |
Drawn at the base of the Pentre-Dwfr Slates where it rests conformably upon the Pen-y-Glog Group, namely the Pen-y-Glog Slates. |
Definition of Upper Boundary: |
Drawn at conformable upward passage of the Glyn Dyfrdwy Group; thin-bedded shales, silty mudstones almost perfectly cleaved to fine-grained uncleaved sandstones and roughly cleaved sandy shales of the Nant-y-Bache Group. |
Thickness: |
304 metres approx. |
Geographical Limits: |
Llangollen, North Wales. |
Parent Unit: |
none recorded or not applicable
|
Previous Name(s): |
none recorded or not applicable
|
Alternative Name(s): |
Nantglyn Mudstone Formation
|
Stratotypes: |
Type Area |
Llangollen area. |
Reference(s): |
Wedd, C B, Smith, B and Wills, L J. 1927. The geology of the country around Wrexham, Part 1. Lower Palaeozoic and Lower Carboniferous rocks. Memoir of the Geological Survey of Great Britain. [London: HMSO.] 179pp. |
Cocks, L R M, Holland, C H, Rickards, R B and Strachan, I, 1971. A correlation of Silurian rocks in the British Isles. Geological Society of London, Special Report No.1. |
Wills, L J and Smith, B, 1922. The Lower Palaeozoic Rocks of the Llangollen district with special reference to Tectonics. Quarterly Journal of the Geological Society, Vol.78, p.176-226. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
none recorded or not applicable |