| Computer Code: |
COMM |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Albian Age (KA)
— Cenomanian Age (KE) |
| Lithological Description: |
The Commodore Formation consists of white to light grey, calcareous, fine- to medium-grained sandstones, interbedded with thin grey mudstones and white to pale grey limestones. The sandstones are locally coarse and may contain intraformational pebbles, glauconite and comminuted shell fragments (Meadows et al. 1987). |
| Definition of Lower Boundary: |
The base of the Commodore Formation is normally marked by a sharp downward change from sandstones into grey mudstones of the Cruiser Formation. This is marked by an abrupt rise in gamma-ray values and a drop in sonic velocity. |
| Definition of Upper Boundary: |
The top of the Commodore Formation is usually marked by a downward change from the interbedded limestones, mudstones and thin sandstones of the Svarte Formation into more uniform sandstones. It is marked on wireline logs by a drop to lower gamma-ray values, and a small increase in sonic velocity. |
| Thickness: |
In the type well it is 312.5 m thick, reducing to less than 40 m in 205/10-2B, 206/5-1 and 208/26-1. Its westerly limit is unknown, although it proved to be absent in 214/29-1Z. The thickest section (947 m) is recorded in 206/11-1. Further south the unit thins rapidly. |
| Geographical Limits: |
The Commodore Formation is restricted to the Faeroe-Shetland Basin. |
| Parent Unit: |
Cromer Knoll Group (CRKN)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 206/03- 1: 3458-3770.5 m (11345-12370 ft) (Ritchie et al., 1996). |
| Reference Section |
North Sea well 205/10- 2B: 4894-4927.5 m (16056-16166 ft) (Ritchie et al., 1996). |
| 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.) |
| Meadows, N S, Macchi, L, Cubitt, J M, and Johnson, B. 1987. Sedimentology and reservoir potential in the West of Shetland area, UK exploration area. In: Brooks, J, and Glennie, K W (eds.) Petroleum Geology of North-West Europe. (London: Graham and Trotman), 723-736. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
