The BGS Lexicon of Named Rock Units — Result Details

Thornton Mudstone Member [Obsolete Name And Code: See KRM]

Computer Code: THMU Preferred Map Code: notEntered
Status Code: Index Level
Age range: Anisian Age (TA) — Anisian Age (TA)
Lithological Description: Mudstone and siltstone, interlaminated, with rhythmic alternation between reddish brown and greenish grey intervals. Halite occurs at base and top.
Definition of Lower Boundary: Conformable, at the gradational upward transition from predominantly structureless reddish brown mudstones (Sidmouth Mudstone Formation, undifferentiated) to the laminated reddish brown and greenish grey mudstones of the Thornton Mudstone Member.
Definition of Upper Boundary: Conformable, at the gradational upward transition from the laminated reddish brown and greenish grey mudstones of the Thornton Mudstone Member to the halite of the Preesall Halite Member.
Thickness: 71m to 112m (Wilson and Evans, 1990).
Geographical Limits: North Fylde peninsula, Lancashire.
Parent Unit: Sidmouth Mudstone Formation (SIM)
Previous Name(s): Thornton Mudstone (-2880)
Thornton Mudstones (-3724)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Thornton Clevelys Borehole (SD34SW/15), Fylde, Lancashire, full sequence proved between 87.85 m and 209.00 m depth. Curated core held at the National Geosciences Records Centre, BGS Keyworth. Wilson and Evans (1990). 
Reference(s):
Warrington, G, Audley-Charles, M G, Elliott, R E, Evans, W B, Ivimey-Cook, H C, Kent, P E, Robinson, P L, Shotton, F W and Taylor, F M. 1980. A correlation of the Triassic rocks in the British Isles. Special Report of the Geological Society of London, No.13. 
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. 
Wilson, A A and Evans, W B. 1990 Geology of the country around Blackpool. Memoir of the British Geological Survey, Sheet 66. (England and Wales). 
Jackson, D I, Johnson, H and Smith, N J P. 1997. Stratigraphical relationships and a revised lithostratigraphical nomenclature for the Carboniferous, Permian and Triassic rocks of the offshore East Irish Sea Basin. 11-32 in Petroleum Geology of the Irish Sea and Adjacent Areas. Meadows, N S, Trueblood, S P, Hardman, M and Cowan, G. (editors). Geological Society Special Publication, No.124. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable