| Computer Code: |
JUSA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Anisian Age (TA)
— Anisian Age (TA) |
| Lithological Description: |
The Judy Sandstone Member consists of beds of massive fluvial sandstone, usually less than 20 m thick, interbedded with silty mudstone. The sandstones are olive-grey, pinkish grey, brown or yellow, and are mainly very fine or fine grained. They are feldspathic and argillaceous, and notably micaceous. The mudstones are grey, greenish grey, olive, reddish brown or brownish grey, and locally contain stringers of dolomite and traces of anhydrite. The unit typically displays erratic log profiles, and average gamma-ray values higher than those of the overlying Julius Mudstone Member (e.g. 30/12b-3). |
| Definition of Lower Boundary: |
The base of the Judy Sandstone Member is defined by a downward change from sandstones to uniform silty mudstones of the Smith Bank Formation. It is marked by a sharp downward increase in the density/neutron separation, and by a downward change to relatively uniform gamma-ray and velocity log signatures. |
| Definition of Upper Boundary: |
The top of the Judy Sandstone Member is defined by a downward change from mudstone (Julius Mudstone Member) to sandstone and mudstone, marked by a downward decrease in velocity and density (e.g. 30/7a-7). |
| Thickness: |
The Judy Sandstone Member varies between 60 and 400 m in thickness. |
| Geographical Limits: |
The Judy Sandstone Member occurs over much of Quadrant 30, possible equivalents being present at the base of the Skagerrak Formation in Quadrant 29. These consist of relatively low-gamma sandstones with few interbedded mudstones, overlain by relatively high gamma mudstones, which may correlate with the Julius Mudstone Member. |
| Parent Unit: |
Skagerrak Formation (SKAG)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 30/12b- 3: 4457-4551 m (14622-14932 ft) below KB (Cameron, 1993). |
| Reference Section |
North Sea well 30/07a- 7: 3445-3821 m (11302-125 36 ft) (Cameron, 1993). |
| Reference(s): |
| Cameron, T D J. 1993. 4. Triassic, Permian and pre-Permian 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. |
| Goldsmith, P J, Rich, B, and Standring, J. 1995. Triassic correlation and stratigraphy in the South Central Graben, United Kingdom North Sea. In: Boldy, S A R (ed.) Permian and Triassic rifting in NW Europe. Geological Society, London, Special Publication. |
| Hodgson, N A, Farnsworth, J, and Fraser, A J. 1992. Salt-related tectonics, sedimentation and hydrocarbon plays in the Central Graben, North Sea, UKCS. In: Hardman, R F P (ed.) Exploration Britain: Geological insights for the next decade. Geological Society, London, Special Publication No.67, 31-63. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
