The BGS Lexicon of Named Rock Units — Result Details

Prismatic Clay Member

Computer Code: PRIS Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Generally a dull brown or reddish brown, sandy silty clay with well dispersed fine pebbles and sparse ironstone nodules. The Prismatic Clay derives its name from the closely spaced, subvertical, prismatic jointing that formed during dry periglacial conditions.
Definition of Lower Boundary: Generally a planar, subhorizontal to undulating gradational boundary with dark brown or purplish brown, stony silty sandy clay diamicton of the Horden Till Formation. Where thin deposits of sand and gravel intervene locally, the Prismatic Clay forms pipes and load structures into the underlying sand and gravel. Locally conformably overlies reddish brown sandy silty clay formerly assigned to the Pelaw Clay by Smith (1994), but containing chalk and flint.
Definition of Upper Boundary: Generally the ground surface. Locally concealed by blown sand.
Thickness: Generally about 0.5m but up to 1.5m
Geographical Limits: Coast of County Durham and southern Northumberland.
Parent Unit: Horden Till Formation (HNTI)
Previous Name(s): Prismatic Clay (-2985)
Alternative Name(s): Upper Clays
Pelew Clay
Stratotypes:
Type Section  250m of cliff section in the vicinity of Warren House Gill, 500-750m south of Horden Point. Smith and Francis, 1967. 
Reference(s):
Francis, E A. 1970. Quaternary. 134-152 in Johnson, G A L, Geology of Durham County. [Newcastle: Natural History Society of Northumberland, Durham and Newcastle-upon-Tyne.] 152pp. 
Bridgland, D R, Horton, B P and Innes, J B. 1999. The Quaternary of northeast England. Field Guide. Quaternary Research Assocation, London. 
Thomas, G S P. 1999. Northern England. 91-98 in Bowen, D Q (Editor), A revised correlation of Quaternary and Neogene deposits in the British Isles. Geological Society Special Report No.23. 
Smith, D B, 1994. Geology of the country around Sunderland. Memoir of the British Geological Survey, Sheet 21, (England and Wales). 
Smith, D B and Francis, E A. 1967. Geology of the country between Durham and West Hartlepool. Memoir of the Geological Survey of Great Britain, Sheet 27 (England and Wales). 
Huddart, D. 2002. Warren House Gill. 51-56 in Huddart, D and Glasser, N F (editors), Quaternary of Northern England. Geological Conservation Review Series, No.25. [Peterborough: Joint Nature Conservation Committee.] 745pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable