The BGS Lexicon of Named Rock Units — Result Details
Cerig Formation
| Computer Code: | CER | Preferred Map Code: | Cer |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Aeronian Age (SA) — Telychian Age (ST) | ||
| Lithological Description: | Grey to green mudstones with dark burrow mottles. Units of dark laminated hemipelagite common in lower half of formation in slope settings, rare to absent on shelf. Sparse thin sandstones. NOTE: At Llandovey (type area) it is underlain by either the Derwyddon Formation or the Wormwood Formation and overlain by the Gwernfelen Formation. In the Rhayader district it overlies the Henfryn Formation or rests disconformably on earlier Formations. It is overlain by either the Dolfawr Mudstones or the Builth Mudstones. | ||
| Definition of Lower Boundary: | Either disconformable on earlier Llandovery or Ashgill or conformable with Henfryn Formation. In latter case junction is gradational but taken at the base of the first thick mudstone bed above the pebbly mudstones, conglomerates and sandstones of the Henfryn Formation. | ||
| Definition of Upper Boundary: | Either at the base of the incoming of thinly interbedded laminated and burrowed mudstones of the Dolfawr Mudstones, or at the base of the incoming of pervasively laminated mudstones of the Builth Mudstones. | ||
| Thickness: | 15 - 480m | ||
| Geographical Limits: | Central Wales. | ||
| Parent Unit: | Not Applicable (-) | ||
| Previous Name(s): | [Obsolete Code: Use CER]
(*13)
Bryn Bedwen Formation [Obsolete Name And Code: Use CER] (BB) Tarannon Pale Shales [Obsolete Name and Code: Use CER] (-1420) Bryn Bedwen Formation [Obsolete Name and Code: Use CER] (-3912) Pale Shales [Obsolete Name and Code: Use CER, DOL] (-3913) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Section | West side of lane leading from Llandovery to Myddfai, opposite the entrance to Cefn Cerig Farm (see fig.64 of Cocks, and others, 1984). | ||
| Reference(s): | |||
| Cocks, L R M, Woodcock, N H, Rickards, R B, Temple, J T, and Lane, P D. 1984. The Llandovery Series of the type area. Bulletin of the British Museum (N.H.), Geology, Vol.38, p.131-182. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E179 | |||