| Computer Code: |
SKSA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Aptian Age (KP)
— Aptian Age (KP) |
| Lithological Description: |
The Skiff Sandstone Member is a unit of mass flow sandstones and interbedded mudstones. Sandstones are very fine- to medium- grained and white to buff. They vary from friable to tightly cemented by calcite. The thin calcite-cemented layers are marked by high velocity peaks on the sonic log. Thick upward-fining sandstones are common and can be recognised on wireline logs by upward increasing gamma-ray motifs (e.g. wells 16/12A-8 and 16/17-15). Some sandstones do not fine upward and have a more blocky gamma-ray signature (e.g. Well 16/17-15). The interbedded mudstones are dark grey and mainly non-calcareous, with low velocity on wireline logs, and are typical of the Carrack Formation. Locally (e.g. 16/12a-8) thin beds of red-brown, calcareous mudstones occur. |
| Definition of Lower Boundary: |
The base of the member is taken at the sharp downward change from sandstones to dark grey, essentially non-calcareous, low velocity mudstones (Carrack Formation). On wireline logs the boundary is marked by a sharp downward increase in gamma-ray values and a downward decrease in velocity. |
| Definition of Upper Boundary: |
The top of the member is normally marked by a downward change from dark grey, essentially non-calcareous mudstones (Carrack Formation) to sandstones with minor mudstones. It does not necessarily coincide with the top of the first sandstone in the Carrack Formation, but is taken at the log breaks associated with the top of the sandstone-rich section. |
| Thickness: |
Up to 65 m thick. |
| Geographical Limits: |
South Viking Graben (North Sea Blocks 16/12 and 16/17). |
| Parent Unit: |
Carrack Formation (CRRC)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 16/12a- 8 at 3799-3861.5 m below KB (Johnson and Lott, 1993). |
| Reference Section |
North Sea well 16/12a- 4 at 4062.5-4080.5 m (Johnson and Lott, 1993). |
| Reference(s): |
| Johnson, H and Lott, G K. 1993. 2. Cretaceous 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 |
