The BGS Lexicon of Named Rock Units — Result Details
Llanbedr Formation
| Computer Code: | LBR | Preferred Map Code: | Lbr |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Comley Series (EC) — Comley Series (EC) | ||
| Lithological Description: | Cleaved purple, green or bluish-grey mudstone with some siltstone and sandstone beds. | ||
| Definition of Lower Boundary: | Rests conformably on rocks of the Dolwen Formation; transitional boundary between dominantly sandstone and siltstone sequence of the Dolwen Formation and the mudstone dominated beds above. | ||
| Definition of Upper Boundary: | Overlain conformably by sandstones of the Rhinog Formation. Boundary taken at the base of the first thick pale green turbiditic sandstone of the Rhinog Formation. | ||
| Thickness: | 90m in the Dolwen pericline, 180m to the west, near Harlech. | ||
| Geographical Limits: | Around the Dolwen Pericline; Harlech southwards towards Barmouth, where it is very poorly exposed. | ||
| Parent Unit: | Harlech Grits Group (HGG) | ||
| Previous Name(s): | Llanbedr Slates [Obsolete Name and Code: Use LBR]
(-356)
Llanbedr Slates And Equivalents [Obsolete Name And Code: Use LBR] (LSL) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Partial Type Section | Afon Crawcwellt, 115m upstream of Pont-Llyn-y-cafn. Basal stratotype. | ||
| Reference(s): | |||
| Allen, P M, Jackson, A A, and Rushton, A W A. 1981. The stratigraphy of the Mawddach Group in the Cambrian succession of North Wales. Proceedings of the Yorkshire Geological Society, Vol. 43, 295-329. | |||
| 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. | |||
| 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. | |||
| Matley, C A and Wilson, T S. 1946. The Harlech Dome, North of the Barmouth Estuary. Quarterly Journal of the Geological Society of London, Vol.102, 1-40. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E135 E149 | |||