The BGS Lexicon of Named Rock Units — Result Details

Grenzanhydrit Formation

Computer Code: GRZH Preferred Map Code: notEntered
Status Code: Full
Age range: Guadalupian Epoch (PUG) — Lopingian Epoch (PUL)
Lithological Description: The Grenzanhydrit Formation consists of white, pale grey and pale orange or red-brown anhydrite that is variously described as soft and amorphous or hard and microcrystalline, sometimes friable, brittle or sucrosic. Locally the Grenzanhydrit Formation contains a unit of red-brown and grey anhydritic claystone and mudstone (e.g. 47/13-2) or white, yellow or red, clear to opaque halite (e.g. 47/15-1).
Definition of Lower Boundary: The lower boundary of the Grenzanhydrit Formation is normally marked by a sharp downward change from white and pale grey anhydrite to halite, K/Mg salts and local, redbrown, saliferous mudstones of the Aller Halite Formation. It coincides with a downward decrease in density and velocity and an increase in gamma values.
Definition of Upper Boundary: The top of the Grenzanhydrit Formation is normally marked by a sharp downward change from red-brown anhydritic mudstone and siltstone of the Bunter Shale Formation to white and pale grey anhydrite. It coincides with a sharp downward increase in velocity and density and a sharp decrease in gamma values.
Thickness: Its thickest development is around the northern margin where it reaches 5-8 m (e.g. 36/26-1). Sections of 2-5 m thickness occur over much of the western and southern parts of the basin (e.g. 47/13-2), thinning to 1 m or less close to the southern feather-edge (e.g. 49/26/4). Over the central part of the basin, the formation is usually less than 2 m thick, but is locally absent or below wireline-log resolution.
Geographical Limits: The Grenzanhydrit Formation is widely distributed across the Southern North Sea Basin.
Parent Unit: Zechstein Group (ZG)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  North Sea well 36/26- 1: 975.5-982.5 m (3200-3224 ft) (Johnson et al., 1994). 
Reference Section  North Sea well 47/13- 2: 2208-2212 m (7244-7257 ft) (Johnson et al., 1994). 
Reference Section  North Sea well 49/26- 4 (Rhys, 1974, table 2, fig. 3): 1526.5-1527.5 m (5009-5012 ft) (metric conversion revised) (Johnson et al., 1994). 
Reference(s):
Cameron, T D J. 1993. 4. Triassic, Permian and pre-Permian of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. 
NAM and RGD (Nederlandse Ardolie Maatschappij and Rijks Geologische Dienst) 1980. Stratigraphic nomenclature of the Netherlands. Transactions of the Royal Dutch Geological and Mining Society of Delft. 
Rhys, G H. 1974. A proposed standard lithostratigraphic nomenclature for the southern North Sea and an outline structural nomenclature for the whole of the (UK) North Sea. Report of the Institute of Geological Sciences, 74/8. 
Smith, D B. 1980. The evolution of the English Zechstein basin. In: Fuchtbauer, H, and Peryt, T M (eds.) The Zechstein basin with emphasis on carbonate sequences. Contributions to Sedimentology 9, 7-34. 
Smith, D B. 1989. The late Permian palaeogeography of north-east England. Proceedings of the Yorkshire Geological Society, Vol.47, 285-312. 
Smith, D B, Harwood, G M, Pattison, J and Pettigrew, T H. 1986. A revised nomenclature for Upper Permian strata in eastern England. 9-17 in Harwood, G M and Smith, D B (editors). The English Zechstein and Related Topics. Geological Society Special Publication No.22. 
Johnson, H, Warrington, G and Stoker, S J. 1994. 6. Permian and Triassic 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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable