Etive Formation (elevated)
(From NPD Bulletin no. 3)
Brent Group
Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type formation
UK well 211/29-3 (Shell), from 2772 m to 2783 m, coord N 61°08'06", E 01°43'36.5" (Fig. 10).
Well reference sections
Norwegian wells 33/9-1 (Mobil), from 2575 m to 2602 m, coord N 61° 15'07.5"
E 01 "50'25.8" (Fig. 11), 30/6-7 (Norsk Hydro), from 2727 m to 2786 m, coord N 60°38' 39.49'' E 02°45'21.74" (Fig. 16), and 31/4-4 (Norsk Hydro) from 2721 m to 2758 m, coord N60°40'01.12", E03°06'54.12", (Fig. 17).
Thickness
11 m in the type well, 27 m in 33/9-1, 59 m in 30/6-7 and 37 m in 31/4-4.
Lithology
The formation consists of massive grey-brown to clear, fine to coarse, occasionally pebbly and cross-bedded sandstones. The mica-content is generally low. Calcite cemented stringers are also present, especially on the Horda Platform.
Boundaries
The formation is characterised by low gamma ray readings. This characteristic and the low mica content distinguish it from the underlying Rannoch Formation. The lower boundary may, however, be transitional in places. The formation is often found to cut into and occasionally through the underlying formations, thus giving a «blocky» gamma ray log character either above a truncated Rannoch Formation, or directly above marine shales of the Dunlin Group (ref. well 31/4-4). The upper boundary is taken at the first significant shale or coal in the overlying Ness Formation.
Distribution
The distribution of the Etive Formation is essentially the same as that of the Brent Group.
Occurrences of formation tops in wells
Age
Bajocian
Depositional environment
The formation has been interpretated as upper shoreface, barrier bar, mouth bar and distributary channel deposits.
