| Computer Code: |
PSA |
Preferred Map Code: |
Ps |
| Status Code: |
Full |
| Age range: |
Soudleyan Substage (OY)
— Longvillian Substage (OL) |
| Lithological Description: |
Fine- to coarse-grained, locally magnetitic sandstones with abundant sedimentary structures. |
| Definition of Lower Boundary: |
Conformably overlies ash-flow tuffs and subordinate sediments of the Capel Curig Volcanic Formation. |
| Definition of Upper Boundary: |
Sharply but conformably overlain by thinly interbedded siltstones and mudstones and siltstones of the undivided Cwm Eigiau Formation. |
| Thickness: |
100 to 200m |
| Geographical Limits: |
Snowdonia, North Wales. |
| Parent Unit: |
Cwm Eigiau Formation (CEI)
|
| Previous Name(s): |
Pren-Teg Grit [Obsolete Name and Code: Use PSA]
(-1776)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Basal stratotype exposed in crags 160m northeast of Hendre Selar, north of Tremadog, North Wales. Howells, M F and Smith, M. 1997. |
| Reference(s): |
| Howells, M F and Smith, M. 1997. Geology of the country around Snowdon. Memoir of the British Geological Survey, Sheet 119 (England and Wales). (London: The Stationery Office). 104pp. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E119
|
