| Computer Code: |
RNB |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Berriasian Age (KR)
— Berriasian Age (KR) |
| Lithological Description: |
The Runcton Member comprises 'bright green, glauconitic, clayey sands with much nodular phosphorite' and, at North Runcton, the 'friable brown phosphatic nodules contain Subcraspedites (V.) lamplughi' (Casey, 1973). A horizon of black phosphatic nodules occurs at the base. At West Dereham, the Runcton Member is reduced to a single band of rolled phosphatic nodules 0.15–0.30 m thick. The member can be traced offshore into The Wash, where it passes into the lower part of the Spilsby Sandstone Formation (lower Spilsby Sandstone) (Wingfield et al., 1978). |
| Definition of Lower Boundary: |
Green, glauconitic, clayey sand with a basal black phosphatic nodule horizon (Runcton Member), rests with a sharp disconformable contact, on grey and yellow-green silty sands with pyrite (Roxham Member). |
| Definition of Upper Boundary: |
'Glauconitic clayey sands with bands of brown-weathering clay ironstone and (especially near the base) seams of phosphorite' (Mintlyn Member) rests with a sharp disconformable contact on 'bright green, glauconitic, clayey sands with much nodular phosphorite' (Runcton Member) (Casey, 1973). |
| Thickness: |
Up to 2 m. |
| Geographical Limits: |
The member is kown best in the Runcton-Mintlyn region, Norfolk, but has been mapped from east of King's Lynn (sheets 145 and 146) south to the east of Downham Market (sheets 159 and 160). Although included in the vertical section of sheet 129, the member is not shown on the face of the map, and is presumed to be obscured by superficial deposits. Offshore, in The Wash, boreholes have penetrated the member, although it is not clear where the Runcton Member passes laterally into the lower part of the Spilsby Sandstone Formation (which is recorded on the northern side of The Wash, in southern Lincolnshire). |
| Parent Unit: |
Sandringham Sands Formation (SAS)
|
| Previous Name(s): |
Runcton Beds [Obsolete Name and Code: Use RNB]
(-2396)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
North Runcton [TF 65 15]. |
| Reference Section |
Temporary trench (No. 2 Gas Feeder Trench) at Manor Farm [TF 6515 1555], North Runcton once exposed the complete member (Casey, 1973). |
| Reference(s): |
| Casey, R and Gallois, R W. 1973. The Sandringham Sands of Norfolk. Proceedings of the Yorkshire Geological Society, Vol.41, 1-22. |
| Gallois, R W. 1984. The Late Jurassic to Mid Cretaceous rocks of Norfolk. Bulletin of the Geological Society of Norfolk, Vol.34, 3-64. |
| 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). |
| Rawson, P F. 1992. Cretaceous, 355-388 in Duff, P McL D and Smith, A J (editors), Geology of England and Wales. (London: Geological Society.) |
| 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.] |
| Hopson, P M, Wilkinson, I P and Woods, M A. 2008. A stratigraphical framework for the Lower Cretaceous of England. British Geological Survey. British Geological Survey Research Report, RR/08/03. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E145
E129
E159
|
