The BGS Lexicon of Named Rock Units — Result Details

Wych Mudstone Member

Computer Code: WYM Preferred Map Code: WyM
Status Code: Full
Age range: Ladinian Age (TD) — Ladinian Age (TD)
Lithological Description: Structureless reddish brown mudstones with anhydrite/gypsum nodules mostly in uppermost two thirds of Member.
Definition of Lower Boundary: Top of highest greenish grey and reddish brown laminated unit of the Byley Mudstones.
Definition of Upper Boundary: Base of Wilkesley Halite. Some thin halite bands in Palmer Mann No.12 Borehole have been included in the Wych Mudstones.
Thickness: 186.44m in Wilkesley Borehole (611' 8").
Geographical Limits: Cheshire Basin.
Parent Unit: Sidmouth Mudstone Formation (SIM)
Previous Name(s): Middle Keuper Marl (-4199)
Wych Mudstone Formation (-1289)
Mercia Mudstone Group (Middle Division) (-1288)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  BGS Wilkesley Borehole 752.34 - 938.78m. (2468' 4" - 3080' 2") (SJ64SW/7). 
Reference Section  Core at BGS Keyworth from 50 - 156m depth in Crewe Heat Flow Borehole (BGS) (SJ65SE/6), 5 - 156m depth. 
Partial Type Section  (Intermittent exposure). Sections in Wych Brook (lower half of formation, with gaps). Best exposure in 3.1m mudstone at SJ 4907 4507. 
Reference(s):
Wilson, A A. 1993. The Mercia Mudstone Group (Trias) of the Cheshire Basin. Proceedings of the Yorkshire Geological Society, Vol.49, 171-188. 
Howard, A S, Warrington, G, Ambrose, K, and Rees, J G. 2008. A formational framework for the Mercia Mudstone Group (Triassic) of England and Wales. British Geological Survey Research Report, RR/08/04. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E123