The BGS Lexicon of Named Rock Units — Result Details
Craig-y-Gaer Coral Bed
| Computer Code: | CYGC | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Chadian Substage (CI) — Chadian Substage (CI) | ||
| Lithological Description: | Pale grey, shelly, fossiliferous, crinoid-rich coarse grainstone. | ||
| Definition of Lower Boundary: | The base is placed at a sharp, irregular, partly stylolitized erosion surface where the coarse grainstone at the base of the Craig-y-Gaer Coral Bed rests, locally with angular discordance, on micritic lime mudstones at the top of the underlying Darren Ddu Member of the Coed Ffyddlwn Formation. | ||
| Definition of Upper Boundary: | The upper boundary is locally gradational, but mainly a sharp, stylolitized irregular surface above which are the ooidal grainstones that form most of the Gilwern Oolite Formation. | ||
| Thickness: | 2 to 3m | ||
| Geographical Limits: | Clydach Valley [SO 215 126], on the northeast crop of the South Wales Coalfield. | ||
| Parent Unit: | Gilwern Oolite Formation (GWO) | ||
| Previous Name(s): | Coral Bed
(CORA)
Coral Bed (CORA) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Section | A pinnacle left during quarrying at Craig-y-Gaer [SO 2238 1330] on north side of the Clydach Valley, 2km east of Brynmawr, Blaenau Gwent, South Wales, exposes the bed, here a crinoidal grainstone 2m thick, and the underlying lime mudstones at the top of the Darren Ddu Member of the Coed Ffyddlwn Formation. Barclay, 1989. | ||
| Reference(s): | |||
| George, T N. 1954. Pre-Seminulan Main Limestone of the Avonian Series in Breconshire. Quarterly Journal of the Geological Society of London, Vol.110, 282-322. | |||
| Barclay, W J, Jackson, D I, Mitchell, M, Owen, B, Riley, N J, White, D E, Strong, G E, and Monkhouse, R A. 1989. Geology of the South Wales Coalfield, Part II, the country around Abergavenny. Memoir of the British Geological Survey. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E232 | |||