The BGS Lexicon of Named Rock Units — Result Details

Zeeland Formation

Computer Code: ZELD Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Courceyan Substage (CF) — Brigantian Substage (CX)
Lithological Description: The Zeeland Formation in well 53/12-2 comprises 300 m of pale brown to dark brown, microcrystalline and very finely crystalline dolomitic limestone, with occasional oolitic beds, overlying 150 m of dark brown and dark grey, finely crystalline dolomite. In the Somerton No.1 well (East Anglia), partly equivalent mid to late Dinantian limestones contain partings of grey mudstone, and have fossiliferous beds containing abundant corals, brachiopods, bivalves, bryozoans and crinoids.
Definition of Lower Boundary: Dinantian carbonates of the East Midlands Shelf generally rest on deformed Lower Paleozoic basinal-marine and volcaniclastic sediments (Strank 1987). In the Somerton No.1 well, however, the carbonates overlie a local development of mid-Dinantian sandstones and mudstones. The base of the Zeeland Formation has not been drilled in the UK sector, but the formation is known to rest on Upper Devonian clastic sediments (Famenne Shale) in parts of the southern Netherlands.
Definition of Upper Boundary: The top of the Zeeland Formation is a regional unconformity. Its boundary with overlying late Namurian or Westphalian fluviodeltaic sediments (Millstone Grit Formation or Westoe Coal Formation) is a clearly defined lithological transition, marked by a sharp downhole decrease in gamma-ray response and increase in velocity (e.g. 53/12-2).
Thickness: 53/12-2 penetrated 450 m of Dinantian carbonates where seismic suggests > 1000 m.
Geographical Limits: Because of the scarcity of well penetrations, the distribution of the Zeeland Formation can be determined only by seismic methods. The base and top of the Dinantian carbonates generate high-amplitude seismic reflectors in Quadrants 52 and 53, and the southward convergence of these reflectors defines the southern limit of the carbonate. Their northern limit has been equated with the limit of the top-carbonate reflector in northeastern Quadrant 53 (Cameron et al. 1992). Seismic definition of the carbonates is relatively poor north of East Anglia, though in eastern England they occur to at least as far north as the Number Estuary. Well 53/12-2 penetrated only the uppermost 450 m of Dinantian carbonates in an area where seismic interpretation suggests that they may be locally more than 1 km thick (Cameron et al. 1992). Equivalent carbonates have a proven thickness of 140 m in the Somerton No.1 well (East Anglia). They are more than 500 m thick on parts of the East Midlands Shelf (Strank 1987), are 953 m thick in Dutch well S2-2, and are up to 750 m thick in the Netherlands (van Staalduinen et al. 1979).
Parent Unit: Carboniferous Limestone Supergroup (CL)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Reference Section  North Sea well 53/12-2: 1882-2331 m TD (6174-7650 ft TD) below KB. Note: type section in Dutch Sector North Sea well S2-2: 1883-2836 m (6178-9304 ft) below KB. This well has not been located. 
Cameron, T D J. 1993. 5. Carboniferous and Devonian of the Southern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. 
Adrichem Boogaert, H A Van and Kouwe, W F P (compilers). 1993. Stratigraphic nomenclature of the Netherlands: revision and update of RGD and NOGEPA. Mededelingen van Rijks Geologische Dienst 50. 
Cameron, T D J, Crosby, A, Balson, P S, Jeffery, D H, Lott, G K, Bulat, J, and Harrison, D J. 1992. United Kingdom offshore regional report: the geology of the southern North Sea. (London: HMSO for the British Geological Survey.) 
Strank, A R E. 1987. The stratigraphy and structure of Dinantian strata in the East Midlands, UK. In: Miller, J, Adams, A E and Wright, V P (eds.) European Dinantian environments, 157-175. John Wiley & Sons, Chichester. 
Staalduinen, C J Van, Adrichem Boogaert, H A Van, Bless, M J M, Doppert, J W Chr, Harsveldt, H M, Montfrans, H M Van, Oele, E, Wermuth, R A and Zagwijn, W H. 1979. The geology of the Netherlands. Mededelingen van Rijks Geologische Dienst 31-2, 9-49. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable