The BGS Lexicon of Named Rock Units — Result Details
Dol-cyn-afon Formation
| Computer Code: | DYN | Preferred Map Code: | Dyn |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Tremadoc Series (O1) — Tremadoc Series (O1) | ||
| Lithological Description: | Grey mudstone and silty mudstone and siltstone with bioturbated sandstones locally. | ||
| Definition of Lower Boundary: | Conformable on black mudstones of the Dolgellau Formation. | ||
| Definition of Upper Boundary: | Unconformably overlain by sandstones or conglomerates of the Allt Lwyd Formation (Nant Ffrancon Subgroup), and locally to the southeast of the Harlech Dome by rocks of the Rhobell Volcanic Group. | ||
| Thickness: | 340 to 400m, locally thickening to 900m | ||
| Geographical Limits: | Northern, eastern and southern flanks of the Harlech Dome, Cwm Pennant, Snowdonia. | ||
| Parent Unit: | Mawddach Group (MWG) | ||
| Previous Name(s): | Dol-Cyn-Afon Member [Obsolete Name and Code: Use DYN]
(-4016)
Porthmadog Formation [Obsolete Name and Code: Use DYN] (-4629) Tremadoc Slates [Obsolete Name and Code: Use DYN] (-4630) Cwmhesgen Formation [Obsolete Name And Code: See DYN, DLU] (CHN) Cwm Hesgen Formation [Obsolete Name and Code: Use DYN] (-2162) Afon Gam Formation [Obsolete Name And Code: See DYN] (AFO) Tremadoc Beds (TCB) Glanypwll Formation [Obsolete Name and Code: Use DYN] (-222) Tremadoc Beds (TCB) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Partial Type Section | Basal stratotype, Dol-Cyn-Afon, Upper Mawddach. | ||
| Reference(s): | |||
| Rushton, A W A and Howells, M F. 1998. Stratigraphical framework for the Ordovician of Snowdonia and the Lleyn Peninsula. British Geological Survey Research Report, RR/99/08. | |||
| 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. | |||
| Pratt, W T, Woodhall, D G and Howells, M F. 1995. Geology of the country around Cadair Idris. Memoir of the British Geological Survey, Sheet 149. (England and Wales). (London: HMSO), 111pp | |||
| Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. | |||
| Allen, P M, and Jackson, A A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey, Sheet 135 with part of Sheet 149 (England and Wales). (London: HMSO.) 112 pp. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E119 E135 E149 E118 E120 E134 | |||