The BGS Lexicon of Named Rock Units — Result Details

Blakeney Formation

Computer Code: BLKN Preferred Map Code: notEntered
Status Code: Full
Age range: Guadalupian Epoch (PUG) — Lopingian Epoch (PUL)
Lithological Description: The Blakeney Formation consists of mudstones with interbedded thin anhydrites and localized thin sandstones. The mudstones are commonly dolomitic and anhydritic and usually red-brown, but locally grey or mottled with grey and pale green. They vary from soft to firm, laminated and subfissile to amorphous and waxy. The anhydrite beds vary from soft, white and amorphous to pale grey, microcrystalline or sucrosic. The sandstones reach 4 m thick and are described as white to grey, fine to medium grained, poorly sorted and cemented with dolomite.
Definition of Lower Boundary: The base of the Blakeney Formation is marked by a downward change from red mudstones to buff dolomite of the Zechsteinkalk Formation. It is characterized by a downward decrease in gamma values and an increase in velocity.
Definition of Upper Boundary: The top of the Blakeney Formation is usually marked by a downward change from grey mudstone of the Grauer Salzton Formation to interbedded white amorphous anhydrite and red-brown mudstone. It typically coincides with a downward decrease in gamma values and an increase in velocity.
Thickness: The Blakeney Formation is about 50 m thick.
Geographical Limits: The Blakeney Formation is present across the South Hewett Shelf area, and forms a marginal facies to the Southern Permian Basin. Like the Edlington Formation (formerly Middle Marls of Smith et al., 1974), the Blakeney Formation is roughly coextensive with the flat shelf of the Z1 carbonates (Smith, 1980).
Parent Unit: Zechstein Group (ZG)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea well 53/07- 2: 1541-1591.5 m (5056-5222 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. 
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, 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