The BGS Lexicon of Named Rock Units — Result Details

Reading Formation

Computer Code: RB Preferred Map Code: RB
Status Code: Full
Age range: Thanetian Age (GT) — Ypresian Age (GY)
Lithological Description: Dominantly clay or silty clay, colour-mottled by pedogenetic processes in a humid environment (Buurman, 1980), together with lensoid channel-fill bodies of bioturbated or cross-bedded fine- to coarse-grained sand. In the clays, red hues dominate with a more or less equal proportion of blue-grey and brown. Red to purple sediments decrease towards the east where there were shorter periods of subaerial weathering and pedogenesis, and reducing conditions in ephemeral lagoons. Beds of dark grey or black clay occur locally: these may be of significance for regional correlation at the interface between the upper and the lower parts of the Reading Formation. The proportion of sand beds varies greatly, and may constitute more than half the formation, dominantly in the basal part (e.g. Crane and Goldring, 1991; Ellison and Williamson, 1999, fig. 4). Fine-grained, bioturbated to laminated glauconitic sand with Ophiomorpha burrows is present in the Reading area. Gravelly sands with informational mud-flake breccias have been referred to as a marginal 'Lane End facies' by Daley (1999). See also White (1906). In parts of London, the upper part of the Lower Mottled Clay includes calcrete as diffuse nodules or as a more continuous layer of limestone. The Reading Formation is considered to have been deposited mainly in various fluvial environments within a coastal flood-plain. However, Ellison et al. (1994) point out that primary sedimentary structures in the Reading Formation clays have been largely obscured, mainly by pedogenic processes, and that it is possible that some of the Reading Formation sediments originated in estuarine or other marginal marine environments. Early Eocene (earliest Ypresian), possibly including the latest Paleocene (Thanetian), by reference to magnetostratigraphy and stable isotope stratigraphy.
Definition of Lower Boundary: In the London Basin, the base of the Reading Formation is marked by the upwards change from typically green, glauconitic variably clayey gravelly sands of the Upnor Formation to vari-coloured mottled clays, locally with brownish sands of the Reading Formation. In places, the boundary has been obscured by contemporary pedogenic processes, including the downwards translocation of clay and pigmentation (Ellison et al., 1994; Page and Skipper, 2000). In the Hampshire Basin, the Reading Formation rests unconformably on chalk.
Definition of Upper Boundary: The top of the Reading Formation is generally sharply defined, at an upward change from vari-coloured mottled clay to glauconitic sands and sandy clays of the Harwich Formation, or to sandy clays of the Walton Member (London Clay Formation), or to shelly grey clays of the Upper Shelly Clay (possible Brixton Formation).
Thickness: Up to 39 m (in the Guildford district, Ellison et al., 2002), generally 12 to 20 m. Occurs in two leaves in Central London. In the Farringdon area, the Lower Mottled Clay is mostly between 2 and 4 m thick, but locally more than 5 m, whereas the Upper Mottled Clay is mostly between 4 and 8 m thick.
Geographical Limits: The Reading Formation occurs throughout the north and west of the London Basin, extending into north-east Essex and Suffolk. In central London it is divided into two at the mid-Lambeth Group Hiatus, above which the Upper Mottled Clays pass laterally south and east into the Woolwich Formation. The Reading Formation is absent from north Kent and south Essex (Ellison et al., 1994). The Reading Formation also occurs in the eastern part of the Hampshire Basin, except in the outliers in East Sussex.
Parent Unit: Lambeth Group (LMBE)
Previous Name(s): Woolwich and Reading Beds (-2293)
Reading Beds (-480)
Mottled Clay (Reading Formation) (MCL)
Alternative Name(s): Reading Formation [Duplicate Code: Use RB]
Stratotypes:
Reference Section  Staines 5 Borehole (TQ07SW156) [TQ 0360 7250], 106.21 to 129.74 m depth (Ellison and Williamson, 1999, fig. 6). 
Reference Section  Pincent's Kiln, Theale, Berkshire [SU 6509 7203] (Crane and Goldring, 1991; Daley, 1999). 
Reference Section  Bolter End, Buckinghamshire [SU 7990 1919]. This exposes cross-bedded sands with gravels and intraformational mud-breccias, representing a marginal facies of the Reading Formation (Daley, 1999). 
Reference Section  Old Cement Works, Harefield, London Borough of Hillingdon [TQ 050 899] (Daley, 1999). 
Type Section  Warner's Brickworks, Knowl Hill, Maidenhead [SU 816 797] (Ellison et al., 1994; Kennedy and Sellwood, 1970). 
Reference Section  Jubilee Line Extension Borehole 404T (TQ37NW 2118) [TQ 33638 79604], Bermondsey, London, 25.05 to 29.63 m and 33.77 to 35.09 m depth (Ellison et al., 1994). This borehole passes through the two parts of the Reading Formation, here separated by the Woolwich Formation. 
Reference(s):
Aldiss, D T. 2014. The stratigraphical framework for the Palaeogene successions of the London Basin, UK. British Geological Survey Open Report, OR/14/008. 95pp. 
Curry, D, Adams, C G, Boulter, M C, Dilley, F C, Eames, F E, Funnell, B M, and Wells, M K. 1978. A Correlation of Tertiary rocks in the British Isles. Geological Society of London Special Publication, Vol. 12, 1-72. 
Daley, B. 1999. London Basin: western localities. 73-84 in British Tertiary Stratigraphy. Daley, B, and Balson, P (editors). Geological Conservation Review Series, No. 15. 
Ellison, R A, Williamson, I T and Humpage, A J. 2002. Geology of the Guildford district - a brief explanation of the geological map. Sheet explanation of the British Geological Survey. 1:50 000 Sheet 285 Guildford (England and Wales). 
Ellison, R A, Woods, M A, Allen, D J, Forster, A, Pharaoh, T C and King, C. 2004. Geology of London. Memoir of the British Geological Survey, Sheets 256 (North London), 257 (Romford), 270 (South London), 271 (Dartford) (England and Wales). 
Ellison, R A and Williamson, I T. 1999. Geology of the Windsor and Bracknell district - a brief explanation of the geological map. Sheet Explanation of the British Geological Survey. 1:50 000 Sheet 269 Windsor (England and Wales). 
Ellison, R A, 1983. Facies distribution in the Woolwich and Reading Beds of the London Basin, England. Proceedings of the Geologists' Association, Vol. 94, 311-319. 
Hester, S W. 1965. Stratigraphy and palaeogeography of the Woolwich and Reading Beds. Bulletin of the Geological Survey of Great Britain No. 23, 117-137. 
Kennedy, W.J., Sellwood, B.W., 1970. Ophiomorpha nodosa Lundgren, a marine indicator from the Sparnacian of south-east England. Proceedings of the Geologists' Association 81, 99-110. 
Page, D P, and Skipper, J A E. 2000. Lithological characteristics of the Lambeth Group. Ground Engineering, Vol. 33, 38-43. 
Prestwich, J, 1854. On the structure of the strata between the London Clay and the Chalk etc, part 11. The Woolwich and Reading Series. Quarterly Journal of the Geological Society, Vol.10, p.77. 
Buurman, P. 1980. Palaeosols in the Reading Beds Palaeocene of Alum Bay, Isle of Wight, UK Sedimentology. 27, Vol. 593-606. 
White, H J O. 1906. On the occurrence of quartzose gravel in the Reading Beds at Lane End, Bucks. Proceedings of the Geologists' Association, Vol. 19, 371-377. 
Edwards, R A and Freshney, E C. 1987. Lithostratigraphical classification of the Hampshire Basin Palaeogene Deposits (Reading Formation to Headon Formation) Tertiary Research, Vol.8, 43-73. 
Crane, P R and Goldring, R, 1991. The Reading Formation (late Palaeocene to early Eocene) at Cold Ash and Pincent's Kiln (Berkshire) in the western London Basin. Tertiary Research, Vol.12, 147-158. 
Ellison, R A, Knox R W O'B, Jolley, D W and King, C, 1994. A revision of the lithostratigraphical classification of the early Palaeogene strata of the London Basin and East Anglia. Proceedings of the Geologists' Association, Vol.105, 187-197. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E314 E206 E207 E239 E254 E255 E256 E257 E266 E268 E267 E269 E282 E283 E284