| Computer Code: |
MGSA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Kimmeridgian Age (JD)
— Tithonian Age (JI) |
| Lithological Description: |
Predominantly subarkosic to arkosic, fine- to coarse-grained, locally granulitic, generally poorly sorted sandstones. Sandstones are mostly structureless. Thin bedded sandstones also occur and exhibit ripple and parallel lamination. Heterogeneous muddy sandstone or sandy mudstones also present and contain sandstone and mudstone clasts, contorted sandstone pipes, contorted beds and balls of sandstone. See De'Ath and Schuyleman (1981) and Richards et al. (1981). |
| Definition of Lower Boundary: |
A down-section transition from sandstone or interbedded mudstone and sandstone to predominantly mudstone. The boundary is marked by a down-section increase in average gamma ray values and commonly by a decrease in velocity. |
| Definition of Upper Boundary: |
The top is defined by a down-section change from high gamma mudstones (Kimmeridge Clay) to sandstones accompanied by a down-section decrease in gamma ray values and increase in velocity. |
| Thickness: |
Highly variable up to c. 200 m. |
| Geographical Limits: |
Restricted to the area around the Magnus Field (East Shetland Basin), Blocks 211/7 and 8, plus Blocks 211/12 and 13. |
| Parent Unit: |
Kimmeridge Clay Formation (KC)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 211/12- 3A between the depths 3064 and 3121 m below KB (Richards et al., 1993). |
| Reference Section |
North Sea well 211/12a- 9 between the depths 3175 and 3377.5 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. |
| De'Ath, N G and Schuyleman, S F. 1981. The geology of the Magnus Oil Field. In: Illing, L V and Hobson, G D (eds.) Petroleum Geology of the continental shelf of North West Europe, 342-351. [Heyden & Son, London] |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
