The BGS Lexicon of Named Rock Units — Result Details
Roach Formation
| Computer Code: | ROH | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Barremian Age (KB) — Barremian Age (KB) | ||
| Lithological Description: | Sandy, bioturbated, ooidal-mudstones and very fine-grained, very clayey, bioturbated, partly ooidal sands. Calcite-cemented, ooidal ironstones occur locally. At Hunstanton, sandy, phosphatic ironstone nodule horizons contain shelly fossils. In Lincolnshire, the formation has been informally divided into 'Upper Roach' and 'Lower Roach', separated by an indurated calcareous cemented, ooidal sandstone known as 'Roach Stone'. Boreholes at Hunstanton, Skegness and The Wash show a rhythmic succession of interburrowed and interbedded clay, "chamosite" mud, chamosite ooids, quartz sand and small pebbles of quartz and ironstone. In Northern Lincolnshire it comprises ferruginous, sandy limestone and ferruginous, ooidal mudstones. | ||
| Definition of Lower Boundary: | In northern Lincolnshire, near Brigg, ooidal and ferruginous mudstones, sandstones and limestones (Roach Formation) rest unconformably on friable ferruginous limestone of the Tealby Limestone Formation. In southern Lincolnshire, the base is a minor erosion surface where the ooidal and pebbly mudstones and very fine sandstones (Roach Formation) rest on the smooth, fossiliferous clays (Upper Tealby Clay Member of the Tealby Formation). In Norfolk, the erosion surface separates the Roach Formation from the underlying interbedded, fine-grained sands, ferruginous sandstones, silts and clays (Dersingham Formation) or mudstones (Snettisham Clay Member). | ||
| Definition of Upper Boundary: | In Norfolk the upper boundary is marked by an erosion surface separating the very pebbly, ooidal clay at the base of the overlying Carstone Formation, from the fine-grained clayey sand of the Roach Formation. Burrows extend down about 30cm into the top of the Roach Formation. Boreholes at Skegness and beneath The Wash prove the junction between grey and dark grey mudstone with Prodeshayesites bodei and iridescent fragments of other ammonites (Skegness Clay) and the ooidal mudstones of the underlying Roach Formation. Farther north, pale grey, fossiliferous, calcareous mudstones (Sutterby Formation) are separated from the ooidal mudstones of the Roach Formation by an erosion surface. | ||
| Thickness: | To c.22m. | ||
| Geographical Limits: | In Norfolk, the Roach is seen on the coast at Hunstanton and in boreholes, but it disappears farther south (it is not present in the Gayton Borehole). Its distribution beneath The Wash is known from a number of boreholes and it is identified in Lincolnshire from boreholes and scattered exposures, although it apparently disappears in northern Lincolnshire and is absent at Nettleton Bottom [TF 1257 9856] and Acre House [TF 1117 9701]. | ||
| Parent Unit: | Not Applicable (-) | ||
| Previous Name(s): | Fulletby Beds [Obsolete Name And Code: Use ROH]
(FBB)
Roach Stone [Obsolete Name And Code: Use ROH] (RST) Roach [Stone] (-500) Fulletby Beds [Obsolete Name and Code: Use ROH] (*941) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Skegness Borehole TF56SE9 between depths 46.53m and 68.27m. Gallois, 1994. | ||
| Reference Section | Wash Borehole BGS 72/78 TF64SW1 between depths 24.60 and 46.30m. Wingfield, et al. 1978. | ||
| Reference Section | Hunstanton Borehole TF64SE11 between depths 36.86 and 53.42m. Gallois, 1994. | ||
| Type Area | As the Fulletby Beds (older term for the formation) around Fulletby [TF 300 780] northeast of Horncastle, in Lincolnshire. | ||
| Reference Section | Alford Borehole TF47NW13, "In the grounds of the pumping station" (Swinnerton, 1935). Swinnerton, 1935. | ||
| Reference Section | Hunstanton Beach in excavations close to the low water mark. Gallois, 1975. | ||
| Reference(s): | |||
| 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. | |||
| 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. | |||
| 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. | |||
| Owen, E F and Thurrell, R G. 1968. British rhynchonelloid brachiopods. Bulletin of the British Museum [Natural History], Geology, Vol.16, 99-123. | |||
| 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. | |||
| Gallois, R W. 1975. The base of the Carstone at Hunstanton - Part 11. Bulletin of the Geological Society of Norfolk, No.27, 21-27. | |||
| 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). | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E103 E115 E129 E145 E090 E091 | |||