The BGS Lexicon of Named Rock Units — Result Details

Upper Western Irish Sea Formation

Computer Code: UWIS Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Holocene Epoch (QH)
Lithological Description: Glaciomarine/marine clay and silt with local concentrations of sand. Seismically well-ordered character, exhibiting drape, onlap and progradation features.
Definition of Lower Boundary: Disconformity at top of underlying Cardigan Bay Formation or incised into pre-Quaternary rockhead surface.
Definition of Upper Boundary: Unconformity at base of overlying Surface Sands Formation (the "Y" seismic unconformity surface of Akhurst et al,1997). Locally crops out at sea bed.
Thickness: 10 to 20m, locally thickening to 60m in channel infills.
Geographical Limits: Irish Sea.
Parent Unit: British Coastal Deposits Group (COAS)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Reference Section  Offshore BGS borehole No. 71/62 at 7m to 44m depth and 3 deg 53.8' W and 54 deg 25.4' N, (and borehole 71/41 but no depths), in conjunction with NIREX seismic line 89/29 shotpoints 2621 to 2630. NIREX 1997 a, b. 
Reference Section  Offshore BGS borehole No. 71/64 at 5m to 28m depth and 3 deg 56.4' W and 54 deg 29.1' N. 
Akhurst, M C, Chadwick, R A, Holliday, D W, McCormac, M, McMillan, A A, Millward, D, Young, B, Ambrose, K, Auton, C A, Barclay, W J, Barnes, R P, Beddoe-Stephens, B, James, J C W, Johnson, H, Jones, N S, Glover, B W, Hawkins, M P, Kimbell, G S, MacPherson, K A T, Merritt, J W, Milodowski, A E, Riley, N J, Robins, N S, Stone, P and Wingfield, R T R. 1997. The geology of the west Cumbria district. Memoir of the British Geological Survey, Sheets 28, 37 and 47 (England and Wales). 138pp. 
Jackson, D I et al. 1995. United Kingdom offshore regional report: the Geology of the Irish Sea (London: HMSO for the British Geological Survey). 
NIREX. 1997a. A summary of the correlation and nature of onshore and offshore Quaternary sediments of the Sellafield area. UK NIREX Ltd. Report No SA/97/042. 
Pantin, H M. 1978. Quaternary sediments from the north-east Irish Sea: Isle of Man to Cumbria. Bulletin of the Geological Survey of Great Britain, Vol 64, 1-43. 
NIREX. 1997b. Interpretation of the BNFL/NIREX offshore high resolution seismic data. UK NIREX Ltd. Report No SA/97/042. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: