The BGS Lexicon of Named Rock Units — Result Details

Swanscombe Member

Computer Code: SWCB Preferred Map Code: notEntered
Status Code: Full
Age range: Ypresian Age (GY) — Ypresian Age (GY)
Lithological Description: The Swanscombe Member comprises glauconitic, very silty or sandy clays, sandy silts and sandy clayey silts, which may contain dispersed shells and lignite. It is highly glauconitic and locally gravelly at the base. Ash particles occur in the Swanscombe Member in south-west Essex (Knox, 1983). King (1981) observes that the unit is similar in lithology to the Oldhaven Member, specifically in its western facies (his Tilehurst Member), but that where the units coexist there is a discontinuity between them usually marked by a gravel bed. Also, the fauna differs.
Definition of Lower Boundary: The glauconitic clays and silts of the Swanscombe Member rests on the glauconitic sands silts and clays of the Oldhaven Member, or the Lambeth Group, on a sharp, erosive contact, commonly marked by flint gravel.
Definition of Upper Boundary: The top of the Swanscombe Member is marked by an upwards change from glauconitic clays and silts to non-glauconitic silty clay, some sandy, some gravelly, of the Walton Member (London Clay Formation).
Thickness: Thin (less than 2 m) or absent in the western London Basin, north Kent and the Hampshire Basin. Elsewhere in the London Basin thickens northwards to more than 10 m (King, 1981).
Geographical Limits: The Swanscombe Member is present in much of the London Basin, but absent from the most western areas, from north-east Kent and from parts of London. According to King (1981), the Swanscombe Member passes north-east into his ‘Harwich Member’, which is here assigned to the Wrabness and Orwell members.
Parent Unit: Harwich Formation (HWH)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Disused clay pit at Bean, Swanscombe, Kent (Durkin, 1968; Durkin and Baldwin, 1968; King, 1981, fig. 32)  
Reference(s):
Aldiss, D.T., 2012. The stratigraphical framework for the Palaeogene successions of the London Basin, UK. British Geological Survey Open Report OR/12/004. Available from http://nora.nerc.ac.uk/17121/. 
King, C, 1981. The stratigraphy of the London Clay and associated deposits. Tertiary Research Special Paper No.6. (Backhuys: Rotterdam). 
Durkin, M K. 1968. Notes on the trace fossils at Bean, Kent. Proceedings of the Geologists' Association, Vol. 79, 215-218, IN219-IN210. 
Durkin, M K, and Baldwin, S A. 1968. Field meeting at Abbey Wood and Swanscombe, Kent: Saturday, 14 May 1966. Proceedings of the Geologists' Association, Vol. 79, 211-215. 
Knox, R W O. 1983. Volcanic ash in the Oldhaven Beds of southeast England, and its stratigraphical significance. Proceedings of the Geologists' Association, Vol. 94, 245-250. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable