The BGS Lexicon of Named Rock Units — Result Details
Turbot Anhydrite Formation
| Computer Code: | TBAN | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Guadalupian Epoch (PUG) — Lopingian Epoch (PUL) | ||
| Lithological Description: | The Turbot Anhydrite Formation is largely composed of anhydrite, but includes a widespread argillaceous unit (the Hake Mudstone Member) and local developments of carbonate. A few thin beds of argillaceous, mainly fine or medium grained sandstone have been recorded near its lateral transition to the Bosies Bank Formation. | ||
| Definition of Lower Boundary: | The Turbot Anhydrite Formation is underlain by carbonates of the Halibut Carbonate Formation. Depending on the geographic location, these carbonates are assigned to the Argyll Carbonate Member (Z1), to the Innes Carbonate Member (Z2), or to an undifferentiated Z1/Z2 carbonate unit. The contact is commonly gradational, the boundary being defined where anhydrite replaces carbonate as the dominant lithology. An upper leaf of the anhydrite formation (its Morag Member) rests on the Shearwater Salt Formation across the centre of the Northern Permian Basin, the boundary being relatively sharp. | ||
| Definition of Upper Boundary: | The Turbot Anhydrite Formation is conformably overlain in many sections by clastic sediments of the Heron Group, but it is overlain by post-Triassic sediments in some areas of deep Mesozoic erosion. Its upper boundary is a sharp lithological transition and log break, except in those parts of the South Halibut Basin where anhydrite is interbedded with mudstones in the basal part of the Smith Bank Formation. | ||
| Thickness: | Thicknesses of the Turbot Anhydrite Formation vary considerably over short distances, mainly as a function of primary depositional environment. By analogy with the Southern Permian Basin (Taylor, 1990), thickest anhydrites accumulated on basin-marginal shelves and slopes. The formation is generally between 20 and 120 m thick in the Northern Permian Basin, but it is 180 m thick in well 14/18-1, and 184 m thick in well 8/27-1, where it includes a 40 m sandstone section. Well 9/28a-7 penetrated 475 m of interbedded anhydrite and sandstone units, representing interdigitation of the Turbot Anhydrite and Bosies Bank formations near the basin margin. | ||
| Geographical Limits: | The Turbot Anhydrite Formation extends across most areas of the Northern Permian Basin. It is notably thin or absent, however, above a zone of thick, mainly Zl carbonates that traces from the Halibut Horst across southern Quadrant 15 to the Fladen Ground Spur. It is also absent from areas of deep Mesozoic erosion into the Permian section. Absence of anhydrite at Argyll may be due to dissolution associated with the Mesozoic erosion (Bifani, 1985). | ||
| Parent Unit: | Zechstein Group (ZG) | ||
| Previous Name(s): | Turbot Anhydrite Formation (A) [Obsolete Code: Use TBAN]
(TBSH)
Turbot Anhydrite Formation (B) [Obsolete Code: Use TBAN] (TUAN) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Section | North Sea well 15/26- 1 (Deegan and Scull, 1977, p.7, fig.9): 3087-3115 m (10128-10220 ft) below KB. This is a condensed section and not now considered to be representative. A key reference section is provided by well 14/4-1. | ||
| Reference Section | North Sea well 14/04- 1; 2474.5-2540.5 m (8118—8335 ft) (Cameron, 1993). | ||
| Reference Section | North Sea well 14/20- 2: 2633-2735 m (8638-8974 ft) (Cameron, 1993). | ||
| Reference Section | North Sea well 15/13- 1: 2574.5-2648 m (8446-8688 ft) (Cameron, 1993). | ||
| Reference Section | North Sea well 20/02- 2: 3485-3560.5 m (11433-11681 ft) (Cameron, 1993). | ||
| Reference Section | North Sea well 27/10- 1: 1106-1124 m (3628-3687 ft) and 1369.5-1393 m (4493-4571 ft) (Cameron, 1993). | ||
| Reference(s): | |||
| Ritchie, J D, Gatliff, R W and Riding, J, 1996. 1. Pre - Tertiary lithostratigraphy. In: Stratigraphic Nomenclature of the UK North West Margin. British Geological Survey, Nottingham. | |||
| Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) | |||
| 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. | |||
| Deegan, C E and Scull, B J. 1977. A standard lithostratigraphic nomenclature for the Central and Northern North Sea. Report of the Institute of Geological Sciences, 77/25; NPD Bulletin No.1. | |||
| Taylor, J C M. 1990. Upper Permian-Zechstein. In: Glennie, K W (ed.) Introduction to the petroleum geology of the North Sea, 153-190. Blackwell Scientific Publications, Oxford. | |||
| Bifani, R. 1985. A Zechstein depositional model for the Argyll field. 11-118 in The role of evaporites in hydrocarbon exploration. Taylor, J C M et al. (editors). JAPEC Course Notes No. 39. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| none recorded or not applicable | |||