The BGS Lexicon of Named Rock Units — Result Details
Claxby Ironstone Formation
| Computer Code: | CI | Preferred Map Code: | CI |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Valanginian Age (KV) — Hauterivian Age (KH) | ||
| Lithological Description: | Pale grey to dark brown, ferruginous oolitic, silty clay with varying concentrations of oolitic ironstone and pink or cream, calcareous, siltstone bands at some levels. Chert and quartz grit are found at some horizons. Phosphatic nodules, which occur at some horizons, contain moulds of shelly fossils, including ammonites, belemnites and bivalves. In southern Lincolnshire, the lower part of the formation comprises pale, purple-grey, mottled brown, silty clay [Hundleby Clay Member]. The top of the formation is more calcareous and has been termed "calcareous beds" by some authors. | ||
| Definition of Lower Boundary: | Between Benniworth and Donnington-on Bain [Lincolnshire] the base is defined by a downsection change from grey and brown, ferruginous, oolitic mudstones [Hundleby Clay Member, Claxby Ironstone Formation] [Casey, 1973]. Farther north, where the Hundleby Clay Member is missing, argillaceous, oolitic ironstone is separated from the underlying pale-yellow sandstones [upper part of Spilsby Sandstone Formation] by an erosion surface. At Nettleton a basal conglomerate contains derived fossils from the Spilsby Formation [Casey, 1973; Kelly and Rawson, 1983]. Borehole evidence suggests that below The Wash, bioturbated, shelly silt and glauconitic sand [which appears to be the Hundleby Member] overlies brown ironstone and fine-grained, silty sand [Mintlyn Member of the Sandringham Sands Formation] [Wingfield et al., 1978]. | ||
| Definition of Upper Boundary: | The Claxby Ironstone Formation grades into the overlying Tealby Formation, although a minor erosion surface has been used to separate the calcareous mudstones at the top of the Claxby Ironstone Formation [Upper Claxby Ironstone Member of Gaunt et al., 1992], from the overlying oolitic clays of the Tealby Clay Formation. | ||
| Thickness: | Up to 8 m [an estimated 9 m was recorded at Dalby by Owen and Thurrell, 1968]. | ||
| Geographical Limits: | The southerly extent of the Claxby Formation is below The Wash. It is present in Wash borehole 72/77A, but does not reach the Norfolk coast, where the coeval upper part of the Sandringham Sands Formation is found. The formation extends through southern Lincolnshire as far north as the Brigg district and finally disappears north of Audleby where the Tealby Formation oversteps it. | ||
| Parent Unit: | Not Applicable (-) | ||
| Previous Name(s): | Ferruginous Band [Obsolete Name and Code: Use CI]
(-3299)
Claxby Beds [Obsolete Name And Code: Use CI] (CYB) Claxby Ironstone [Obsolete Name and Code: Use CI] (-2699) Lower Sand and Sandstone [Obsolete Name and Code: Use CI, SYS] (*596) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Alford Borehole, "In the grounds of the pumping station". Swinnerton, 1935. | ||
| Reference Section | Nettleton Top, south west of Caistor. Casey, 1973. | ||
| Reference Section | BGS Wash borehole 72/77B. Wingfield et al., 1978. | ||
| Reference Section | Skegness Borehole. | ||
| Reference Section | Railway cutting between Nenniworth and Donnington-on-Bain. Casey, 1973 | ||
| Reference Section | Nettleton Hill Quarry. | ||
| Reference(s): | |||
| Owen, E F and Thurrell, R G. 1968. British rhynchonelloid brachiopods. Bulletin of the British Museum [Natural History], Geology, Vol.16, 99-123. | |||
| 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.] | |||
| Dikes, W H and Lee, J W. 1837. Outlines of the Geology of Nettleton Hill, Lincolnshire. The Magazine of Natural History, I [No.11], 562-566. | |||
| Judd, J W. 1867. On the strata which form the base of the Lincolnshire Wolds. Quarterly Journal of the Geological Society, London, 23, 227-251. | |||
| Gaunt, G D, Fletcher, T P and Wood, C J. 1992. Geology of the country around Kingston upon Hull and Brigg. Memoir of the British Geological Survey, sheets 80 and 89 (England and Wales). 172pp. | |||
| Swinnerton, H H. 1935. The rocks below the Red Chalk of Lincolnshire and their cephlopod fauna. Quarterly Journal of the Geological Society, London, 91, 1-46. | |||
| Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. | |||
| Kelly, S R A and Rawson, P F. 1983. Some late Jurassic - mid Cretaceous sections on the East Midlands Shelf, England, as demonstrated on a field meeting, 18-20 May 1979. Proceedings of the Geologists' Association, Vol.94, 65-73. | |||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E103 E089 E090 E091 E115 | |||