The BGS Lexicon of Named Rock Units — Result Details
Ceiriad Formation
| Computer Code: | CRAD | Preferred Map Code: | Crd |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | St David's Series (ED) — St David's Series (ED) | ||
| Lithological Description: | Red, brown and green siltstones with subordinate, similarly coloured fine-grained sandstones. | ||
| Definition of Lower Boundary: | Conformably overlies coarse-grained, thickly-bedded turbidites of the Cilan Formation (Harlech Grits Group). | ||
| Definition of Upper Boundary: | Conformably overlain by interbedded grey, blue-grey siltstones and mudstones, with thin beds of pale sandstone, of the Nant-y-big Formation. | ||
| Thickness: | At least 40 m. | ||
| Geographical Limits: | St Tudwal's Peninsula, northwest Wales. | ||
| Parent Unit: | Not Applicable (-) | ||
| Previous Name(s): | Lower Caered Mudstones [Obsolete Name and Code: Use CRAD]
(-4567)
Caered Flags (CAF) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Partial Type Section | Cliffs immediately west of Trwyn Llech-y-doll. For base and lower part of formation. Young, Gibbons, and McCarroll. 2002. | ||
| Partial Type Section | Northwest corner of Porth Ceiriad bay. For upper part of formation. Young, Gibbons, and McCarroll. 2002. | ||
| Reference(s): | |||
| Matley, C A, Nicholas, T C and Heard, A. 1939. Summer field meeting to the western part of the Lleyn Peninsula. Proceedings of the Geologists' Association, Vol.50, 83-110. | |||
| Young, T P, Martin, F, Dean, W T and Rushton, A W A. 1994. Cambrian stratigraphy of St Tudwal's Peninsula, Gwynedd, northwest Wales. Geological Magazine, Vol.131, 335-360. | |||
| 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). | |||
| Nicholas, T C. 1915. Geology of the St Tudwal's Peninsula. Quarterly Journal of the Gelogical Society of London, Vol.71, 83-143. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E134 | |||