The BGS Lexicon of Named Rock Units — Result Details

Mintlyn Member

Computer Code: MNB Preferred Map Code: MnB
Status Code: Full
Age range: Berriasian Age (KR) — Valanginian Age (KV)
Lithological Description: Glauconitic, clayey, grey and green sands with bands and "doggers" of brown-weathering clay-ironstone and seams of phosphatic nodules (picking out erosion surfaces). A prominent band of phosphatic nodules occurs at the base. Casey and Gallois (1973) stated that the member could be divided into two based on ammonite faunas, a lower "Hectoroceras Beds" and an upper division "in which Surites and allies predominate".
Definition of Lower Boundary: The base is taken where glauconitic, clayey, grey and green sands with bands and "doggers" of clay-ironstone and phosphatic nodules (Mintlyn Member) overlies green, glauconitic, clayey sands with abundant phosphatic nodules (Runcton Sand Member).
Definition of Upper Boundary: The upper boundary is placed at the up-sequence change from glauconitic, clayey, grey and green sands with bands and "doggers" of brown-weathering clay-ironstone and seams of phosphatic nodules of the member, up into the unconsolidated, moderately clean, pale grey (occasionally green, yellow or orange), fine- to medium-grained, cross-bedded quartz sands with subordinate bands of silt or clay of the overlying Leziate Member.
Thickness: Up to c. 15 m.
Geographical Limits: The member is known from the east of Gaywood: King's Lynn Bypass (where it is up to 15m thick, e.g. the cutting at Mintlyn Wood); South of Middleton Stop Drain to the North Runcton area; and south as far as the West Dereham area. Several boreholes have penetrated the member, including Hunstanton Borehole (9.7m thick), Marham Borehole (10.3m thick) and Severals House Borehole (0.5m thick - this southward truncation being due to the overstepping Carstone). The member has been traced beneath The Wash (Borehole 72/77B) and apparently passes laterally into the Upper Spilsby Sandstone/ Basal Claxby formations. The "Surites levels" are represented in the Upper Spilsby Sandstone Formation of South Lincolnshire; Casey and Gallois (1973).
Parent Unit: Sandringham Sand Formation (SAS)
Previous Name(s): Mintlyn Beds (-4200)
Mintlyn Sand Member (-4800)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  BGS Wash Borehole 72/77B [TF6313 4835]. The member is encountered between 43.10 and 48.30m depth. Wingfield et al., 1978; Gallois (1994, p.73). 
Type Section  Galley Hill, west of Mintlyn Wood. "The largest and most stratigraphically revealing section yet recorded in the Mintlyn Beds is that in the cutting [6508 1987 to 6530 2010] dug for the King's Lynn Bypass at the western end of Mintlyn Woods." Where 12.95m of the member were visible, Gallois (1994, 68-70 and Figure 26). Casey, 1973; Casey and Gallois, 1973. 
Reference Section  Hunstanton Borehole TF64SE11 [6857 4078]. The member was encountered between 85.42 and 96.83m depth. Gallois (1994, 73-74).. 
Reference Section  Marham Borehole TF70NW1 [7051 0803]. The member is encountered between 54.36 and 68.33m depth. Gallois (1994. p.74). 
Type Section  100m west of Wissington Railway Bridge. See entry for Pratt's Bridge, Roxham. Casey and Gallois, 1973. 
Type Section  About 100m east of Pratt's Bridge, Roxham. "The full thickness of the Mintlyn Beds, unconformably overlain by the Carstone, was exposed at the southern limit of this area of outcrop in the Fenland Flood Relief Channel excavations [TL 639 995 to 662 996] eastwards from Roxham Farm, West Dereham." Here 6.75m of strata were described, Gallois, 1994, 72-73); Casey and Gallois, 1973. 
Reference Section  Severals House Borehole (Wissington Estate Methwold C) TL69NE9 [6930 9650]. Here a thin unit of Lower Greensand strata between "unconformities" at 30.39 and 31.32 depth is interpreted as containing the member. 
Reference(s):
Casey, R 1973. The ammonite succession at the Jurassic-Cretaceous boundary in Eastern England. In Casey, R and Rawson, P F [editors], The Boreal Lower Cretaceous [Liverpool: Seel House Press.] 
Gallois, R W, 1994. The geology of the country around King's Lynn and The Wash. Memoir of the British Geological Survey, Sheet 145 and part of 129 (England and Wales). 
Gallois, R W. 1984. The Late Jurassic to Mid Cretaceous rocks of Norfolk. Bulletin of the Geological Society of Norfolk, Vol.34, 3-64. 
Wingfield, R T R, Evans, C D R, Deegan, S E and Floyd, R. 1978. Geological and geophysical survey of The Wash. Report of the Institute of Geological Sciences, 78/18, 32pp. 
Casey, R and Gallois, R W. 1973. The Sandringham Sands of Norfolk. Proceedings of the Yorkshire Geological Society, Vol.41, 1-22. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E129 E145 E146 E159 E160