The BGS Lexicon of Named Rock Units — Result Details

Stanmore Gravel Formation

Computer Code: STGR Preferred Map Code: notEntered
Status Code: Full
Age range: Early Pleistocene Epoch (QPE) — Early Pleistocene Epoch (QPE)
Lithological Description: Gravel and sand, clayey near base. Gravel mostly composed of flints, up to 150mm in diameter, with a little quartz, quartzite and Lower Greensand chert in the fine fractions. Matrix of orange-brown, pale grey, red mottled clay and sandy clay, with pockets of coarse sand. Locally with layers of silt, clay or peat. Interpreted as offshore or beach gravels (Ellison et al 2004), or possibly fluvial (Bridgland 1994).
Definition of Lower Boundary: Rests unconformably on London Clay bedrock, base of deposit at 105-128 above O.D.
Definition of Upper Boundary: Overlain in places by till of the (Anglian) Lowestoft Formation, but generally at surface.
Thickness: To 7m; average 3m. A thickness of 4.8m is recorded in the BGS Stanmore Common borehole (TQ19SE102).
Geographical Limits: Thames Valley and Colne and Lea valleys region; plateau cappings from Stanmore, Middlesex to Billericay, Essex, and Shooter's Hill, Kent.
Parent Unit: Crag Group (CRAG)
Previous Name(s): Pebble Gravel (-442)
Pebble Gravel Formation [Obsolete Name And Code: See NBED And STGR] (PBGR)
Stanmore Pebble Gravel (-3054)
Warley Gravel (-3055)
Sand And Gravel Of Unknown Age (SGU)
Stanmore Member (-547)
Plateau Gravel (PLG)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Harrow Weald Common. Gibbard, 1999. 
Partial Type Section  Stanmore Common, described in BGS (MAU) boreholes TQ19SE/5 (TQ 1550 9394), and TQ19SE/6 (TQ 1647 9360). 4.80m recorded in BGS Stanmore Common borehole (TQ19SE/102). Ellison et al., 2004. 
Reference(s):
Gibbard, P L. 1999. The Thames Valley, its tributaries and their former courses. 45-58 in Bowen, D Q (Editor), A revised correlation of Quaternary deposits in the British Isles. [London: The Geological Society.] 
Bromehead, C E N. 1925. The Geology of North London. Memoir of the Geological Survey of Great Britain. Sheet 256 (England and Wales). 
Bridgland, D R. 1994. Quaternary of the Thames. Geological Conservation Review Series No.7. (Peterborough: Joint Nature Conservation Committee.) 
Dines, H G and Edmonds, F H. 1925. The geology of the country around Romford. Memoir of the Geological Survey of Great Britain, Sheet 257 (England and Wales). 
Dewey, H, Bromehead, C E N, Chatwin, C P and Dines, H G. 1924. The geology of the country around Dartford. Memoir of the Geological Survey, Sheet 271 (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). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E256 E257