The BGS Lexicon of Named Rock Units — Result Details

Allt-Y-Clych Conglomerate Formation

Computer Code: ACC Preferred Map Code: AcC
Status Code: Full
Age range: Rhuddanian Age (SR) — Rhuddanian Age (SR)
Lithological Description: Conglomerates, pebbly mudstones and sandstones. A few thin mudstone beds.
Definition of Lower Boundary: Sharp and erosional. Taken at base of first bed of pebbly mudstone or conglomerate above the Tycwtta Mudstones or Yr Allt Formation.
Definition of Upper Boundary: Gradational but taken at base of first thick mudstone unit of overlying Pistyll Gwyn Mudstones.
Thickness: 12 - 80 metres.
Geographical Limits: Central Wales, east of Tywi Anticline.
Parent Unit: Not Available (!)
Previous Name(s): Allt-Y-Clych Conglomerate Member (Form Facies) (-1298)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Prominent line of crags running north-east/south-west through the summit of Ally-Y-Clych, Llanafan-Fawr. 
Reference(s):
Lockley, M G. 1978. New Evidence on the age of some Lower Palaeozoic rocks near Llanafan-Fawr. Geological Journal, Vol.13, 15-24. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E179