The BGS Lexicon of Named Rock Units — Result Details

Wentlooge Level Formation

Computer Code: WLLEV Preferred Map Code: notEntered
Status Code: Full
Age range: Holocene Epoch (QH) — Holocene Epoch (QH)
Lithological Description: Soft to very soft, blue-grey clay, with scattered diffuse silt laminae and peats. A basal gravel and diachronous basal peat are commonly present.
Definition of Lower Boundary: In the type area it lies unconformable on bedrock, fluvioglacial sand and gravel of Welsh Ice origin, and locally on Brecknockshire Formation.
Definition of Upper Boundary: Generally the ground surface; locally overlain by deposits of the Severn and Avon Catchments Subgroup.
Thickness: Generally 9 to 12m, though locally more in the region of buried channels. 15m proved in borehole [ST58NW/2] at Sudbrook.
Geographical Limits: Northern shore of the Severn Estuary between Cardiff and Gloucester. Includes Wentlooge Level, Caldicote Level, New Grounds and Minsterworth Ham, as well as tidal banks north of the main channel.
Parent Unit: British Coastal Deposits Group (COAS)
Previous Name(s): Rumney Formation (-612)
Wentlooge Formation (-613)
Northwick Formation (-3133)
Estuarine Alluvium [Obsolete Name And Code: Use TFD] (ESAL)
Tidal Flat Deposits (TFD)
Awre Formation (-1920)
Gwynllwg Formation (-1921)
Alternative Name(s): none recorded or not applicable
Type Area  Coastal plain between Cardiff and Newport on the Wentlooge Level. Tidal flat deposits formed during the post-Devensian global sea-level rise. Allen, 1987 
Allen, J R L. 1987. Late Flandrian shoreline oscillations in the Severn Estuary: the Rumney Formation at its typesite (Cardiff area). Philosophical Transactions of the Royal Society of London, Vol.B315, 157-174. 
Waters, R A and Lawrence, D J D. 1987. Geology of the South Wales Coalfield - Part III: the country around Cardiff. Memoir of the British Geological Survey, Sheet 263. (England and Wales). 
Bowen, D Q, 1999. Wales. Chapter 7 in Bowen, D Q (Editor), A revised correlation of Quaternary deposits in the British Isles. Geological Society of London Special Report, No.23. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E233 E234 E249 E250 E263