| Computer Code: |
SPEK |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Hettangian Age (JH)
— Toarcian Age (JT) |
| Lithological Description: |
Heterolithic, varicoloured, but usually green or grey, unit of sandstones, siltstones and mudstones. |
| Definition of Lower Boundary: |
The lower boundary is defined by the downward change from varicoloured, but usually green or grey, heterolithic sediments to red Triassic sediments (Cormorant Formation). A weak down-section increase in gamma values coincides with the boundary. |
| Definition of Upper Boundary: |
The top is marked by a sharp downward change from sandstone dominated, coal-bearing strata (Fladen Group) to argillaceous, coal-free deposits. The boundary coincides with a sharp down-section increase in gamma values. |
| Thickness: |
Up to c. 100 m. |
| Geographical Limits: |
Unst Basin, North Sea quadrants 1, 2, 209, 210. |
| Parent Unit: |
Dunlin Group (DUNL)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 1/04- 1 between 844 and 945 m below KB (Richards et al., 1993). |
| Reference Section |
North Sea well 1/04- 2 between 731.5 m and 821.5 m (Richards et al., 1993). |
| Reference(s): |
| Richards, P C, Lott, G K, Johnson, H, Knox, R W O'B. and Riding, J B. 1993. 3. Jurassic 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. |
| Johns, C R and Andrews, I J. 1985. The petroleum geology of the Unst Basin, North Sea. Marine and Petroleum Geology, 2, 361-372. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
