The BGS Lexicon of Named Rock Units — Result Details

Ockendon Member

Computer Code: OCKD Preferred Map Code: notEntered
Status Code: Full
Age range: Ypresian Age (GY) — Ypresian Age (GY)
Lithological Description: According to King (1981, 2003) the Ockendon Member can be divided into a lower part (A3i) that comprises silty homogeneous clay with several layers of grey claystones, and an upper part (A3ii) that comprises silty clay with many very thin layers of very fine-grained sand. This also contains claystone but in very thin layers and lenses that are commonly soft and red-brown.
Definition of Lower Boundary: The base of the Ockendon Member is marked by the upwards appearance of homogeneous strata mainly comprising grey clays and claystones with calcareous fossils and calcareous concretions, with less silty clay than in the underlying Walton Member (King, 1981, 2003, in prep.).
Definition of Upper Boundary: The top of the Ockendon Member is marked by the disappearance of thin layers and partings of well-sorted, fine-grained sand (beneath a thin bed of sandy silty clay at the base of the Aveley Member) and a return to mainly homogeneous clay.
Thickness: The Ockendon Member thickens generally eastwards to a maximum of 18m (King, 1981, in prep.).
Geographical Limits: The Ockendon Member is present throughout the Hampshire and London basins, except in the west.
Parent Unit: London Clay Formation (LC)
Previous Name(s): Division A3 (-5088)
Unit B of Ellison et al., 2004 (UNITB)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Staines 5 Borehole (TQ07SW156) from 81.0 to 97.4m depth. (Ellison and Williamson, 1999, fig.6; Ellison et al., 2004, p.46). 
Reference Section  South Ockendon clay quarry (Essex)(cf. the nearby Aveley Quarry, King, 1981,fig. 11). 
Reference(s):
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, 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). 
King, C. in prep. A revised correlation of Palaeogene and Neogene deposits in the British Isles. Geological Society of London Special Report. 
King, C, 1981. The stratigraphy of the London Clay and associated deposits. Tertiary Research Special Paper No.6. (Backhuys: Rotterdam). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable