Computer Code: |
NEPT |
Preferred Map Code: |
notEntered |
Status Code: |
Full |
Age range: |
Hauterivian Age (KH)
— Aptian Age (KP) |
Lithological Description: |
The Neptune Formation consists predominantly of fine- to medium-grained, clear and pale coloured sandstone interbedded with thin mudstones. The sandstones are locally calcareous and glauconitic. The thickest sandstone is 23 m, and like most of the sand units has a sharp top and base characterised by an abrupt rise in gamma-ray values and a drop in sonic velocity. The mudstones are medium to dark brown or grey. In the upper part of the unit, individual sandstones tend to be less than 5 m thick, separated by mudstones less than 2 m thick. Below 4244 m (13925 ft) the gamma-ray response from the sandstones is higher and more irregular than the cleaner sandstones in the upper part of the formation. |
Definition of Lower Boundary: |
In the type well, the Neptune Formation rests unconformably on the Triassic Foula Formation. This is characterised by a higher sonic velocity and a more uniform, but higher, gamma-ray value. |
Definition of Upper Boundary: |
The top of the Neptune Formation is defined by a downward change from the grey mudstones of the Cruiser Formation into interbedded sandstones and mudstones. This is accompanied by a downward decrease in gamma-ray values and an increase in sonic velocity. Occasional gamma-ray spikes in the mudstones are higher than values recorded in the overlying Cruiser Formation. |
Thickness: |
159 m thick. |
Geographical Limits: |
The sandstones of the Neptune Formation are only present in 204/19-1. The formation may be restricted to the southern part of the Faeroe-Shetland Basin, west of the Westray Ridge. |
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 204/19- 1: 4129-4288 m (13547-14069 ft) (Ritchie et al., 1996). |
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.) |
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. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
none recorded or not applicable |