| Computer Code: |
YKH |
Preferred Map Code: |
YkH |
| Status Code: |
Full |
| Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
| Lithological Description: |
Rhyolitic crystal-lithic tuffs, tuffaceous sandstones and breccio-conglomerates. |
| Definition of Lower Boundary: |
The clastic apron deposits lie on Carneddol Rhyolitic Tuff Formation, passing onto Foel Ddu Rhyodacite Tuff Formation. Locally overlies the Penmaen Formation. |
| Definition of Upper Boundary: |
The clastic apron deposits pass upwards into dark grey graptolitic mudstones of the Nod Glas Formation, and part of the Carneddol Rhyolitic Tuff Formation. |
| Thickness: |
50-130m |
| Geographical Limits: |
Pwllheli area, north-west Wales. |
| Parent Unit: |
Llanbedrog Volcanic Group (LIG)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Partial Type Section |
Lower part of formation at Yoke House. |
| Partial Type Section |
Upper part at Cacau Gwynion-isaf. |
| Reference(s): |
| Young, T P, Gibbons, W and McCarroll, D. 2002. Geology of the country around Pwllheli. Memoir of the British Geological Survey, Sheet 134 (England and Wales). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E134
|
