The BGS Lexicon of Named Rock Units — Result Details

Langton Clay Member

Computer Code: LNGC Preferred Map Code: LaC
Status Code: Full
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Mudstone or clay, grey and dark brown with some silt and sand, and sparse belemnites. In the Brown Moor borehole (SE86SW4, Gaunt et al, 1980) a unit inferred to represent the Langton Clay Member comprises mudstone with interbedded siltstone.
Definition of Lower Boundary: The base is poorly exposed. Wright, J K (2009) infers a sharp, downward passage from clay into underlying bioclastic, sandy limestone of the Limekiln Member but this unit has not been recognised in mapping in the York district. Instead, the base is inferred to be marked by a non-sequence of clay and mudstone resting on coralliferous and ooidal limestone of the Coralline Oolite Formation. South from Langton, the Langton Clay Member is inferred to overstep the Coral Rag Member to rest unconformably on the Malton Oolite Member in the Brown Moor borehole (SE86SW4, Gaunt et al, 1980).
Definition of Upper Boundary: The upper boundary is poorly exposed. It is inferred to be sharp, passing upwards from clay/mudstone into variably calcareous sandstone and argillaceous limestone of the North Grimston Cementstone Member. In the Brown Moor borehole (SE86SW4, Gaunt et al, 1980), it is inferred that the basal interbedded mudstone and siltstone of the North Grimston Cementstone Member belongs to the Langton Clay Member, the top of the Langton Clay Member here being marked by the first appearance of limestone.
Thickness: The thickness is estimated to be between 0 and 10m. Approximately 5.5m in the Brown Moor borehole (SE86SW4, Gaunt et al, 1980).
Geographical Limits: Outcrops in the area of the village of Langton and North Grimston, south-east of Malton, North yorkshire. Extends south to the Acklam area in the subcrop.
Parent Unit: Upper Calcareous Grit Formation (UCG)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Langton Beck, near Langton Village, south-east of Malton. Approximately 4m of clay previously exposed and described by C D Wright (1976) as Ampthill Clay. According to Wright, a section 300m to the east was previously seen where the Langton Clay Member is inferred to be overlain by grey, argillaceous sandstone and limestone of the North Grimston Cementstone Member. The nature of the boundary here is not known. For previously observed sections refer to Wright, C D (1976) and Wright, J K (2009). 
Reference(s):
Wright, J K. 2009. The geology of the Corallian ridge (Upper Jurassic) between Gilling East and North Grimston, Howardian Hills, North Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 57, 193-216. 
Wright, C D. 1976. New outcrops of Ampthill Clay north of Market Weighton, North Yorkshire, and their structural implications. Proceedings of the Yorkshire Geological Society, Vol. 41, 127-140. 
Gaunt, G D, Ivimey-Cook, H C, Penn, I E and Cox, B M. 1980. Mesozoic rocks proved by the Institute of Geological Sciences boreholes in the Humber and Acklam areas. Report of the Institute of Geological Sciences, No. 79/13. 
Wright, J K, 1980. Oxfordian Correlation Chart. "In" Cope, C J W, (Editor). A correlation of Jurassic rocks in the British Isles, Part two: Middle and Upper Jurassic. Geological Society of London Special Report No.15. (p.61-76 in Correlation Chart). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E063