Computer Code: |
GORS |
Preferred Map Code: |
notEntered |
Status Code: |
Full |
Age range: |
Oxfordian Age (JO)
— Oxfordian Age (JO) |
Lithological Description: |
Brownish black, paralic mudstones with locally abundant coal fragments. |
Definition of Lower Boundary: |
The basal boundary of the Gorse Member (and Heather Formation) may be conformable or unconformable. It is defined by a down-section passage from mudstones to thinly bedded sandstones, mudstones and coals (Stroma Member, Pentland Formation). It is marked by a sharp down-section decrease in gamma-ray and velocity values. In some sections, the member is seen to rest unconformably on Triassic reddish and grey-brown mudstones (Smith Bank Formation). |
Definition of Upper Boundary: |
The top is defined by a down-section change from grey mudstone (Heather Formation) to brownish black mudstones; a down-section increase in resisitivity, a decrease in velocity and, often, a temporary increase in gamma. |
Thickness: |
Up to c. 60 m. |
Geographical Limits: |
Witch Ground Graben and South Halibut Basin (Outer Moray Firth) (Quadrants 14, 15 and 20). |
Parent Unit: |
Heather Formation (HTHE)
|
Previous Name(s): |
Skene Member
(-5143)
|
Alternative Name(s): |
none recorded or not applicable
|
Stratotypes: |
Type Section |
North Sea well 20/08- 1 between depths 2764 and 2783.5 m below KB (Richards et al., 1993). |
Reference Section |
North Sea well 15/21- 4 between depths 2556.5 and 2569.5 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. |
Harker, S D, Mantel, K A, Morton, D J and Riley, L A. 1993. The stratigraphy of Oxfordian-Kimmeridgian (Late Jurassic) reservoir sandstones in the Witch Ground Graben, UK North Sea. American Association of Petroleum Geologists Bulletin, 77, 1693-1709. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
none recorded or not applicable |