The BGS Lexicon of Named Rock Units — Result Details
Foel Y Ddinas Mudstones Formation
| Computer Code: | FYD | Preferred Map Code: | Fyd |
|---|---|---|---|
| Status Code: | Pending Upgrade | ||
| Age range: | Hirnantian Age (OH) — Hirnantian Age (OH) | ||
| Lithological Description: | Dark blue silty mudstones. Includes Calettwr Quartzite and Hirnant Limestone at the top of the formation. | ||
| Definition of Lower Boundary: | Base succeeds grey siltstones, mudstones and thin sandstone laminae of the Moelfryn Mudstones. | ||
| Definition of Upper Boundary: | Top - succeeded by striped dark-blue shales with subsidiary siltstones of the Cwm-yr-Aethnen Mudstones. | ||
| Thickness: | 125 metres. | ||
| Geographical Limits: | Not defined. | ||
| Parent Unit: | Not Applicable (-) | ||
| Previous Name(s): | Foel Y Ddinas Mudstones [Obsolete Name and Code: Use FYD]
(-3411)
Foel-Y-Ddinas Mudstones [Obsolete Name And Code: Use FYD] (FDMA) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | Bala, Sheet 136. | ||
| Reference(s): | |||
| Bassett, D A, Whittington, H B, and Williams, A. 1966. The stratigraphy of the Bala district, Merionethshire. Quarterly Journal of the Geological Society of London, Vol. 122, 219-271. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E120 E136 | |||