The BGS Lexicon of Named Rock Units — Result Details
Bifidus Slate Formation
| Computer Code: | BFDS | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Pending Upgrade | ||
| Age range: | Abereiddian Stage (O2) — Abereiddian Stage (O2) | ||
| Lithological Description: | Mudstones with localised conglomerates, siltstones, tuffaceous debris flow deposits (Tal-y-Gareg Member). | ||
| Definition of Lower Boundary: | Marked by rapid transition from massively bedded tuffs or tuffaceous sediments of the Beacon Hill Volcanic Formation. | ||
| Definition of Upper Boundary: | Marked by transition from bluish or olive green mudstones into nodular black mudstones (Fron Neurydd Formation). | ||
| Thickness: | 95m (Sheet SH50NE) to 200m (Cadair Idris - Cox, 1925, Quarterly Journal of the Geological Society of London, Vol.81. | ||
| Geographical Limits: | Continuous outcrop from the coast to beyond Cadair Idris. | ||
| Parent Unit: | Aran Volcanic Group (AVG) | ||
| Previous Name(s): | Bifidus Beds
(-690)
Bifidus Slates [Obsolete Name and Code: Use CREN, BFDS] (-1346) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| none recorded or not applicable | |||
| Reference(s): | |||
| Jones, B, 1933. The geology of the Fairbourne-Llwyngwril district, Merioneth. Quarterly Journal of the Geological Society, Vol.89, 145-171. | |||
| 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 | |||
| Ridgeway, J. 1975. The stratigraphy of Ordovician volcanic rocks around the south and east of the Harlech Dome in Merionethshire, North Wales. Geological Journal, Vol.10, 87-106. | |||
| Cox, A H. 1925. The geology of the Cadair Idris Range, (Merioneth). Quarterly Journal of the Geological Society of London, Vol.81, p.539-592. | |||
| Cox, A H, and Wells, A K. 1921. The Lower Palaeozoic rocks of the Arthog-Dolgellau district (Merionethshire). Quarterly Journal of the Geological Society, London, Vol.76, p. 254-324. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E149 | |||