| Computer Code: |
SLPE |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Cisuralian Epoch (PLC)
— Lopingian Epoch (PUL) |
| Lithological Description: |
The Silverpit Evaporite Member is characterized by reddish brown mudstones and siltstones with beds of halite. The halite beds are up to about 25 m thick and are typically massive and hard, brittle, coarsely crystalline and clear to translucent or white and reddish brown in colour. Locally, minor amounts of white to pink, amorphous anhydrite are associated with the halites (e.g. 3599.5-3609 m in 43/25-1). |
| Definition of Lower Boundary: |
The base of the Silverpit Evaporite Member is typically placed at the base of the lowest, massive halite bed in the Silverpit Formation. This is generally associated with a marked downward increase in gamma-ray values and a sharp decrease in resistivity. Locally, the Silverpit Evaporite Member lies unconformably on the Carboniferous Conybeare and Whitehurst groups (e.g. 44/22-1). |
| Definition of Upper Boundary: |
The top of the Silverpit Evaporite Member is typically placed at the top of the highest, massive halite bed in the Silverpit Formation. This does not necessarily coincide with the highest occurrence of halite, but typically corresponds to a marked downward decrease in gammaray values and a sharp increase in resistivity. Locally, thin, 'ratty halites' are present above the top of the Silverpit Evaporite Member (e.g. 3226.5-3257 m in 44/22-1). In the depocentre of the Silverpit Formation, the halite beds are generally thicker, more numerous, and apparently range to higher stratigraphic levels (e.g. 44/22-1). |
| Thickness: |
The Silverpit Evaporite Member reaches up to about 200 m thick. |
| Geographical Limits: |
The Silverpit Evaporite Member is present in the southern part of the Silver Pit Basin (i.e. the south of quadrants 43 and 44) and extends into the Dutch sector. It is absent near the northern, western and southern limits of the Silverpit Formation. However, an isolated patch of thick halites is recorded in the Silverpit Formation in well 48/7b-5, to the west of the main development of the Silverpit Evaporite Member. |
| Parent Unit: |
Silverpit Formation (SLVP)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 44/21- 1: 4063.5-4185 m (13331-13730 ft) below KB (Johnson et al., 1994). |
| Reference Section |
North Sea well 44/22- 1: 3262.5-3453.5 m (10703-11330ft) (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, 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.) |
| George, G T, and Berry, J K. 1993. A new lithostratigraphy and depositional model for the Upper Rotliegend of the UK Sector of the Southern North Sea. In: North, C P, and Prosser, D J (eds.) Characterization of fluvial and aeolian reservoirs. Geological Society, London, Special Publication No.73, 291-319. |
| Glennie, K W. 1972. Permian Rotliegendes of northwest Europe interpreted in light of modern desert sedimentation studies. AAPG Bulletin 56, 1048-1071. |
| Glennie, K W. 1990. Lower Permian - Rotliegend. In: Glennie, K W (ed.) Introduction to the Petroleum Geology of the North Sea, Blackwell Scientific Publications, p. 120 - 152. |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
