The BGS Lexicon of Named Rock Units — Result Details

Llwyn-Y-Brain Formation [Obsolete Name And Code: Use LYMD]

Computer Code: LYM Preferred Map Code: LYM
Status Code: Index Level
Age range: Rhuddanian Age (SR) — Rhuddanian Age (SR)
Lithological Description: Interbedded silty mudstones, grey-buff, and thin fine-grained sandstones; some mass flow and slumped strata, including coarse sandstones and conglomerate.
Definition of Lower Boundary: Not seen, but probably unconformable upon strata of mid-Caradoc age.
Definition of Upper Boundary: Not seen.
Thickness: Unknown.
Geographical Limits: Western side of the Severn Valley around Berriew and Fron. Sheets 151 (Welshpool) and 165 (Montgomery).
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  As type section, also Rose Hill where there is a basal conglomerate and mass flow pebbly mudstone (equivalent to Powis Castle Conglomerate). 
Type Section  Behind large water tank, 90m, 080 degrees from Llwyn-y-Brain, Garthmyl. 
Reference(s):
none recorded or not applicable
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E165 E151