| Computer Code: |
SER |
Preferred Map Code: |
SER |
| Status Code: |
Index Level |
| Age range: |
Abereiddian Stage (O2)
— Abereiddian Stage (O2) |
| Lithological Description: |
[Obsolete: use BGL, RBVO]
Mudstone with thick irregular lenses of laharic breccias and volcanic conglomerates. Thin and very localised grits occur, and tuffaceous units. |
| Definition of Lower Boundary: |
Base of mudstones succeeding Henllan Ash - feldspathic sandstones. |
| Definition of Upper Boundary: |
Top marked by basal ash-flow tuff of the Llyn Conwy Formation. |
| Thickness: |
380 metres. Lateral variation, 0-380 metres. |
| Geographical Limits: |
Not defined. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Snowdon, Sheet 119. |
| Reference(s): |
| British Geological Survey. 1993. Corwen, provisional. England and Wales sheet 120. Solid and drift, 1:50 000 (Southampton: Ordnance Survey for British Geological Survey.) |
| Lynas, B D T, 1973. The Cambrian and Ordovician rocks of the Migneint area, North Wales. Journal of the Geological Society, London, Vol.129, 481-503. |
| Zalasiewicz, J A. 1992. Graptolite dating of Ordovician vulcanicity in the Arenig area, North Wales. Geological Journal, Vol.27, 379-389. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E120
|
