Hod Formation (Hodformasjonen)

(From NPD Bulletin no. 5)

Shetland Group


Named by Deegan & Scull (1977) from the Hod Field in Norwegian block 2/11. The name Hod derives from one of the twelve principal gods in Norse mythology. Hod was a son of Odin.

Well type section

Norwegian well 1/3-1 from 4343 to 3828 m, coordinates N 56°51'21.00", E 01°51'05.00" (Fig. 24). No cores.

Well reference sections

UK well 29/25-1 from 2225 to 2012 m, coordinates N 56°18'10.00", E 01°51'48.80" (Fig. 26). No cores.
Norwegian well 2/8-8 from 2601 to 2494 m, coordinates N 56°16'50.28", E 03°24'15.93" (Fig. 28). 36 m of cores discontinuously through the upper 78 m and lowermost 6 m of the formation.


The formation is 515 m thick in the type well, 213 m in UK well 29/25-1 and 107 m in Norwegian well 2/8-8. In the Norwegian sector, seismic interpretation indicates that the formation may reach a thickness of more than 700 m in the northwestern part of the Central Trough.


In the type well the formation consists of hard, white to light grey, crypto- to microcrystalline limestones which may become argillaceous or chalky in places. White, light grey to light brown, soft to hard chalk facies may dominate the formation or alternate with limestones. The limestones may be pink or pale orange. Thin, silty, white, light grey to green or brown, and soft, grey to black, calcareous clay/shale laminae are occasionally present. Pyrite and glauconite may occur throughout the formation and the latter may be common in the lower part.

Basal stratotype

The lower boundary is usually marked by a distinct log break to a lower gamma-ray response and higher velocity from the Blodøks Formation to the Hod Formation (Fig. 24). The boundary may be less distinct when the Blodøks Formation is more calcareous (Fig.31).

Characteristics of the upper boundary

The upper boundary towards the Tor Formation is generally marked by a change in gamma-ray readings to a more constant and slightly lower level, and also by higher velocity, (Figs. 24 and 31). The upper boundary may represent an unconformity in the Ekofisk area (e.g. Norwegian well 2/8-8, Fig. 28).


The formation is widely distributed in central and eastern parts of the central North Sea, passing laterally into sediments of the Herring and Flounder Formations to the west and the Tryggvason and Kyrre Formations to the northwest.


Turonian to Campanian.

Depositional environment

Open marine with deposition of cyclic pelagic carbonates (periodites) and distal turbidites (Skovbro 1983 and d'Heur 1986).


An informal, tripartite subdivision of the Hod Formation into lower, middle and upper members is often possible in the southern part of the Central Trough in the Norwegian sector. The subdivision is based on the frequent presence of a higher clay content in the middle of the Hod Formation (Figs. 24, 28 and 29).

Lower member of the Hod Formation: This unit constitutes the largest part of the Hod Formation and is a sequence of bioturbated laminated chalks with a low clay content. It occurs in Norwegian wells 1/3-1 from 4343 to 4066 m, 2/8-8 from 2601 to 2538 m and 1/9-1 from 3648 to 3353 m.

Middle member of the Hod Formation: This is a sequence consisting mainly of periodites, which generally have a greyish colour reflecting a marked increase in terrigenous clay. It is shown on well logs as an increase in gamma-ray readings. It occurs in Norwegian wells 1/3-1 from 4066 to 4009 m, 2/8-8 from 2538 to 2518 m and 1/9-1 from 3353 to 3344 m.

Upper member of the Hod Formation: This unit constitutes another sequence dominated by periodites with minor allochthonous intercalations, but with a return to a low clay content. It occurs in Norwegian wells 1/3-1 from 4009 to 3828 m, 2/8-8 from 2518 to 2494 m and 1/9-1 from 3344 to 3312 m.

The Herring Formation of Deegan & Scull (1977) includes a similar lithology and was deposited at the same time as the Hod Formation. It is regarded here as the lower part of the Hod Formation. The Hod Formation is also equivalent in age to the Tryggvason and Kyrre Formations (Fig. 6).

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