The BGS Lexicon of Named Rock Units — Result Details

Retford Member

Computer Code: RTF Preferred Map Code: notEntered
Status Code: Full
Age range: Olenekian Age (TO) — Olenekian Age (TO)
Lithological Description: Mudstone and siltstone, greenish grey, intercalated with subordinate reddish-brown mudstone; thin beds of varicoloured fine- to medium-grained sandstone, laminated and micaceous, are common throughout. Veins and nodules of gypsum are common locally. A thin calcareous conglomerate occurs locally at the base.
Definition of Lower Boundary: Slightly unconformable, at an abrupt upward change from red-brown pebbly sandstones of the Sherwood Sandstone Group to the greenish grey mudstones at the base of the Retford Member. In north Nottinghamshire, the Retford Member is separated from the Sherwood Sandstone Group by a tongue of reddish brown mudstone and siltstone that thickens towards the northeast.
Definition of Upper Boundary: Conformable, within a gradational, upward transition from greenish-grey mudstones and siltstones of the Retford Member to the predominantly brown mudstones, siltstones and fine-grained micaceous sandstones of the overlying undifferentiated Tarporley Siltstone Formation.
Thickness: Maximum 21m in northeast Nottinghamshire, thinning to 6m south of Ollerton, pinches out at the northern outskirts of Nottingham.
Geographical Limits: Mapped at outcrop in central and north Nottinghamshire, and proved in boreholes in the adjacent subcrop to the east.
Parent Unit: Tarporley Siltstone Formation (TPSF)
Previous Name(s): Green Beds "Sensu Stricto" (-1151)
Green Keuper Basement Beds (-3010)
Retford Formation (-3011)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Thrumpton Goods Yard cutting, northeast of East Retford railway station, Nottinghamshire. Smith eta al., 1973. 
Reference Section  Fulbeck F/B1 Borehole (SK85SE/25), Fulbeck, Lincolnshire, full sequence proved between 364.60m and 375.24m depth. Curated core held at the National Geosciences Records Centre, BGS Keyworth. Berridge et al., 1999. 
Reference(s):
Smith, E G and Warrington, G. 1971. The age and relationships of the Triassic rocks assigned to the lower part of the Keuper in north Nottinghamshire, north-west Lincolnshire and south Yorkshire. Proceedings of the Yorkshire Geological Society, Vol.38, 201-227. 
Berridge, N G, Pattison, J, Samuel, M D A, Brandon, A, Howard, A S, Pharaoh, T C and Riley, N J. 1999. Geology of the Grantham district. Memoir of the British Geological Survey, sheet 127 (England and Wales). 
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. 
Smith, B. 1924. On the West Cumberland Brockram and its associated rocks. Geological Magazine, Vol.61, 289-308. 
Smith, E G, Rhys, G H and Goossens, R F. 1973. Geology of the country around East Retford. Memoir of the Geological Survey of Great Britain, Sheet 101 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable