The BGS Lexicon of Named Rock Units — Result Details

Preesall Halite Member

Computer Code: PRSA Preferred Map Code: notEntered
Status Code: Full
Age range: Anisian Age (TA) — Ladinian Age (TD)
Lithological Description: Halite, with thin partings of reddish brown and dark greenish grey mudstone. Breccias formed by dissolution are common at shallow depth.
Definition of Lower Boundary: Conformable, at the gradational upward transition from the laminated reddish brown and greenish grey mudstones (formerly referred to the Thornton Mudstone Member, now undifferentiated Kirkham Mudstone Member) to the halite of the Preesall Halite Member.
Definition of Upper Boundary: Conformable, at the gradational upward transition from the halite of the Preesall Halite Member to the predominantly greenish grey laminated mudstone at the base of the overlying undifferentiated Kirkham Mudstone Member (formerly referred to the now Obsolete Coat Walls Mudstone Member).
Thickness: 100m to 150m (Wilson and Evans, 1990).
Geographical Limits: Preesall Saltfield, north Fylde peninsula, Lancashire, and (as the Preesall Halite Formation, q.v.) in adjacent parts of the East Irish Sea Basin.
Parent Unit: Sidmouth Mudstone Formation (SIM)
Previous Name(s): Preesall Salt (-1775)
Alternative Name(s): none recorded or not applicable
Type Area  Numerous boreholes between Preesall and the River Wyre (Preesall Saltfield), north Fylde peninsula, Lancashire. Borehole sections described in Wilson and Evans, 1990 
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). 
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. 
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. 
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. 
Wilson, A A. 1990. The Mercia Mudstone Group (Trias) of the East Irish Sea Basin. Proceedings of the Yorkshire Geological Society, Vol.48, 1-22. 
Evans, W B. 1970. The Triassic salt deposits of north-western England. Quarterly Journal of the Geological Society, London, Vol.126, 103-123. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: