The BGS Lexicon of Named Rock Units — Result Details

Dolhir Formation

Computer Code: DO Preferred Map Code: DO
Status Code: Pending Upgrade
Age range: Ashgill Series (OA) — Ashgill Series (OA)
Lithological Description: Micaceous siltstones and mudstones with subsidiary sandstone and limestone bands. Variable basal limestone (Dolhir Limestone Member) to fissile mudstone (Tyn-y-Twmpath Member). Formation has rich shelly (brachiopod) fauna. Includes Corwen Grit Member at top of formation.
Definition of Lower Boundary: Unconformable on various Caradoc Formations.
Definition of Upper Boundary: Top of Corwen Grit Member succeeded by pale grey-green siltstones and mudstones of the Fron Frys Formation.
Thickness: 490 metres. Lateral variations, 320 - 490 metres.
Geographical Limits: Not defined.
Parent Unit: Not Applicable (-)
Previous Name(s): Dolhir Beds (-869)
Alternative Name(s): none recorded or not applicable
Type Area  Wrexham, Sheet 121. 
Hiller, A, 1981. The Ashgill rock of the Glyn Ceiriog district, north Wales. Geological Journal, Vol.16, p.181-200. 
Brenchley, P J, 1978. The Caradocian rocks of the North and West Berwyn Hills. Geological Journal, Vol.13, 137-164. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E120 E136 E150 E137