The BGS Lexicon of Named Rock Units — Result Details

Maerdy Mudstone Formation [Obsolete Name And Code: Use MFN]

Computer Code: MAE Preferred Map Code: MAE
Status Code: Index Level
Age range: Ashgill Series (OA) — Ashgill Series (OA)
Lithological Description: Grey to bluish grey siltstones with subordinate grey, light grey, yellow and white fine-grained sandstones and siltstone laminae which are parallel or ripple-laminated. Bioturbated. Rare macrofauna. Includes Dinas Sandstone Member at top of formation.
Definition of Lower Boundary: Unconformable on various Caradoc Formations.
Definition of Upper Boundary: The Dinas Sandstone Member is overlain by pale grey siltstones of the Bettws Mudstone or Bron-y-Graig Formations.
Thickness: 1600 metres. Lateral variations, 1000 metres - 1600 metres.
Geographical Limits: Not defined.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Area  Corwen Sheet 120. 
Alder, K E, 1976. The geology of an area around Bettws Gwerfil Goch and Melin-y-Wig. Unpublished PhD Thesis, University of Cambridge. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: