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:
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 Section  Core at BGS Keyworth from 50 - 156m depth in Crewe Heat Flow Borehole (BGS) (SJ65SE/6), 5 - 156m depth. 
Type Section  BGS Wilkesley Borehole 752.34 - 938.78m. (2468' 4" - 3080' 2") (SJ64SW/7). 
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