| Computer Code: |
MOUS |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Eocene Epoch (GE)
— Eocene Epoch (GE) |
| Lithological Description: |
The Mousa Formation consists predominantly of poorly consolidated, variably glauconitic, locally shelly, fine to coarse grained sandstone. In some sections, the sandstones are massively bedded (e.g. 15/21-1), whereas in others they are interbedded with thin mudstones (e.g. 9/16-1). Most sections include at least one relatively thick unit of glauconitic, grey to grey-brown or grey-green silty mudstone or siltstone. Individual sandstone units mostly show blocky gamma-ray and resistivity log signatures, indicating little vertical variation in grain size. However upward-coarsening trends are often displayed in the basal unit of each major sandstone package (e.g. 15/4-1), and small-scale, discrete upward-coarsening units are often present in the uppermost part of the formation. |
| Definition of Lower Boundary: |
In the Northern North Sea, the Mousa Formation overlies the Balder Formation, the boundary being defined by a gamma-ray peak and by a downward change to grey, tuffaceous mudstone. In the Outer Moray Firth, it overlies either the Dornoch Formation (e.g. 15/4-1) or the Balder Formation (e.g. 15/21-1). In both cases, the base of the Mousa Formation is marked by a unit of high-gamma glauconitic mudstone resting on sandstone, lignite, or grey, non-glauconitic mudstone. |
| Definition of Upper Boundary: |
The top of the Mousa Formation is marked by a downward change from highly glauconitic silty mudstone or siltstone to sandstone with a significantly lower glauconite content. A marked gamma-ray peak is commonly present at the base of the overlying Skade Formation (e.g.15/4-1). |
| Thickness: |
The Mousa Formation is commonly between 200 to 300 m thick. |
| Geographical Limits: |
The Mousa Formation is restricted to western parts of the North Sea Basin, but appears to have a northern limit within Quadrant 3 and a southern limit within Quadrant 27. |
| Parent Unit: |
Stronsay Group (STRY)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 15/04- 1: 504-942 m (1653-3090 ft) below KB (Knox and Holloway, 1992). |
| Reference Section |
North Sea well 9/07- 1: 880-1052 m (2887-3452 ft) (Knox and Holloway, 1992). |
| Reference Section |
North Sea well 9/16- 1: 474.5-1067.5 m (1557-3502 ft) (Knox and Holloway, 1992). |
| Reference Section |
North Sea well 15/21- 1: 629-1100 m (2064-3608 ft) (Knox and Holloway, 1992). |
| Reference(s): |
| 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.) |
| Knox, R W O'B and Holloway, S. 1992. 1. Paleogene 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
