Heather Formation

(From NPD Bulletin no. 3)

Viking Group

Members of Formation

Fenris Member | Fraoch Member |


Named by Deegan and Scull (1977).

Well type section

UK well 211/21-1A (Shell), from 2810 m to 2840 m, coord N 61°11'9.6", E 01°06'5.7", (Fig. 18, NPD Bulletin no. 3).

Well reference sections

Norwegian wells 33/9-1 (Mobil), from 2450 m to 2464m, coord N61°15°07.5" E01°50'25.8" (Fig. 11), 31/2-1 (Shell) from 1531.5 m to 1594.5 m, coord N 60°46'19.16'°, E 03°33' 15.87" (Fig. 21), and 15/3-1 (Elf) from 4754 m to 4986 m, coord N 58°50'57.0", E01°43' 13.25", (Fig. 19).


30 m in the type well, but attains thicknesses in the order of a thousand metres in graben areas. In the reference wells the thicknesses are 14 m (33/9-1), 63 m (31/2-1) and 232 m (15/3-1).


The formation consists of mainly of grey silty claystone with thin streaks of limestone. A further subdivision of the formation is possible (Fig. 18), although no formal status is proposed for this subdivision. Two divisions are commonly recognized. The lower division is light to dark grey, hard, silty claystone, often micaceous and calcareous. The upper division is separated into two further units by an unconformity detected by dipmeter data or biostratigra-phical gaps, but no distinct lithological difference is noted. The lithology is dark grey silty claystone, carbonaceous in part with limestone streaks. (For further discussion see Deegan and Scull (1977) p. 18). On the Horda Platform where the Heather Formation interdigitates with sandstones of the Krossfjord, Fensfjord and Sognefjord Formations, it becomes in places highly micaceous and may grade into a sandy siltstone.


The lower boundary is the contact with the arenaceous Brent Group. The upper boundary is the contact with the Draupne Formation, which has an anomalously high gamma ray response and low velocity. Both boundaries are therefore marked by log breaks.


The formation can be recognized over most of the northern North Sea north of 58°N and east of the East Shetland Platform boundary faults.


Bathonian to Kimmeridgian

Depositional environment

The silty claystones of the Heather Formation were deposited in an open marine environment, brought about by the marine transgression which initially deposited the youngest formation of the Brent group.


Use of the Heather Formation is here restricted to the part of the North Sea north of approximately 58°N. Deegan and Scull (1977) indicated the presence of the formation in the Central Graben, but did not describe the area in any detail. Recent work (e.g. Ofstad 1983, and this report) suggests a subdivision of the Middle Jurassic-earliest Cretaceous claystones of this region into three new formations. None of these can alone be referred to the northern Heather Formation, and the name has therefore not been used in the southern area.