The BGS Lexicon of Named Rock Units — Result Details

Pegmatitanhydrit Formation

Computer Code: PGHY Preferred Map Code: notEntered
Status Code: Full
Age range: Guadalupian Epoch (PUG) — Lopingian Epoch (PUL)
Lithological Description: The Pegmatitanhydrit Formation consists of distinctive, white to grey, occasionally pale orange anhydrite that is variably soft, firm or hard, amorphous or crystalline (sucrosic) to microcrystalline. Locally the formation may contain interbedded halite (e.g. 47/13-2) or dark red-brown mudstone (e.g. 49/21-1).
Definition of Lower Boundary: The lower boundary of the Pegmatitanhydrit Formation is defined by a sharp downward change from white-grey anhydrite to red-brown, saliferous mudstones of the Roter Salzton Formation. It coincides with a sharp downward decrease in density and velocity and a downward increase in gamma-ray values. Where the Pegmatitanhydrit Formation is thinly developed and/or the underlying Roter Salzton Formation contains abundant halite and potassium salts the boundary is less well defined, particularly on the gamma log (e.g. 44/22-3).
Definition of Upper Boundary: The top of the Pegmatitanhydrit Formation is normally marked by a sharp downward change from halite of the Aller Halite Formation to white-grey anhydrite (e.g. 47/13-2). It is characterized on wireline logs by a sharp downward increase in density and velocity. The gamma log response to this boundary is variable, although there is commonly no significant downward change. Locally, a slight downward decrease is seen on the gamma log due to the presence of high gamma, argillaceous/potassic halite at the base of the Aller Halite Formation (e.g. 41/25a-l and 49/26-4).
Thickness: It is generally around 9 m thick in a 60-90 km-wide marginal zone around the basin except in the southeast where the maximum thickness reached is 5 m. It is locally absent or not recognizable in the centre of the basin due to deformation resulting from halokinesis (e.g. 43/26-5), but where present the formation is commonly only thinly developed.
Geographical Limits: The Pegmatitanhydrit 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 41/25a- 1: 1168.5-1177.5 m (3834-3863 ft) (Johnson et al., 1994). 
Reference Section  North Sea well 49/26- 4 (Rhys, 1974, table 2, fig. 3): 1587-1588 m (5206-5210 ft) (Johnson et al., 1994). 
Reference(s):
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. 
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. 
Cameron, T D J, Crosby, A, Balson, P S, Jeffery, D H, Lott, G K, Bulat, J, and Harrison, D J. 1992. The geology of the southern North Sea. United Kingdom offshore regional report. (London: HMSO for the British Geological Survey.) 
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. 1989. The late Permian palaeogeography of north-east England. Proceedings of the Yorkshire Geological Society, Vol.47, 285-312. 
Smith, D B, Brunstrom, R G W, Manning, D I, Simpson, S and Shotton, F W. 1974. A correlation of Permian rocks in the British Isles. Geological Society of London Special Report No. 5. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable