The BGS Lexicon of Named Rock Units — Result Details

Cardigan Bay Formation

Computer Code: CBAY Preferred Map Code: CBF
Status Code: Full
Age range: Marine Isotope Stage 6 (QMIS006) — Marine Isotope Stage 2 (QMIS002)
Lithological Description: Upper and lower tabular unstratified (till) members, laterally grading to sands and gravels, separated by an intervening lenticular and tabular infill member. The Lower Till Member comprises stiff clay, abundant pebbles, slightly pebbly sand with shell clasts, together suggestive of a sub-glacial lodgement till, and elsewhere includes sands interpreted as ice-proximal glaciomarine deposits. The lenticular component comprises sands with subordinate muds, whereas the associated overlying tabular beds consist of fine-grained silty sands and sandy clays. The Upper Till Member comprises a stiff to hard diamicton of clay with varying content of sand, gravel, shell, cobbles and boulders.
Definition of Lower Boundary: An erosion surface with a gentle topographic variation of about 15 m on the underlying St George's Channel Formation. Locally on pre-Quaternary erosion surface.
Definition of Upper Boundary: Unconformity at base of overlying Upper Western Irish Sea Formation. Locally crops out at sea bed.
Thickness: 28 to 158 m.
Geographical Limits: Offshore, eastern Irish Sea.
Parent Unit: Brython Glacigenic Group (BRYG)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Offshore BGS borehole No. 71/64 at 28 m to 77 m depth and 54 deg 29.1' N, 3 deg 96.4' W. 
Partial Type Section  Borehole NX40SE/3, Point of Ayre, Isle of Man, from surface to 111 m depth (Smith, 1931). 
Reference Section  Offshore BGS borehole No. 71/62 at 44 m to 77 m depth and 54 deg 25.4' N, 3 deg 53.8' W (and borehole 71/41 but no depths noted), in conjunction with NIREX seismic line 89/29 shot points 2621 to 2630. 
Reference(s):
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. 
Stoker, M S, Balson, P S, Long, D, and Tappin, D R. 2011. An overview of the lithostratigraphical framework for the Quaternary deposits on the United Kingdom continental shelf. British Geological Survey Research Report, RR/11/03. 48pp. 
Hession, M A. 1988. Quaternary geology of the South Irish Sea. Unpublished PhD thesis, University of Aberystwyth. 
Tappin, D R, Chadwick, R A, Jackson, A A, Wingfield, R T R and Smith, N J P. 1994. United Kingdom offshore regional report; the geology of Cardigan Bay and Bristol Channel. (London: HMSO for the British Geological Survey.) 
Cameron, T D J, and Holmes, R. 1999. The Continental Shelf. 125-139 in A revised correlation of Quaternary deposits in the British Isles. Bowen, D Q (editor). Special Report of the Geological Society of London, No. 23. 
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. 
NIREX. 1997b. Interpretation of the BNFL/NIREX offshore high resolution seismic data. 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. 
Smith, B. 1931. Borings through the glacial drift of the northern plain of the Isle of Man. Summary of Progress of the Geological Survey of Great Britain (for 1930), No.3, 14-23. 
McMillan, A A, Hamblin, R J O, and Merritt, J W. 2011. A lithostratigraphical framework for onshore Quaternary and Neogene (Tertiary) superficial deposits of Great Britain and the Isle of Man. British Geological Survey Research Report, RR/10/03. 343pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E037