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Tryggvason Formation (new) (Tryggvasonformasjonen)

(From NPD Bulletin no. 5)

Shetland Group


Named after Olav Trygvason, a Norwegian king (A.D 995-1000),

Well type section

Norwegian well 25/1-1 from 3790 to 3582 m, coordinates N 59°53'17.40", E 02°04'42.70" (Fig. 33). No cores.

Well reference sections

Norwegian well 35/3-2 from 3190 to 2864 m, coordinates N 61°5r05.98", E 03°46'28.22" (Fig. 34). No cores.
Norwegian well 24/9-1 from 3783 to 3638 m, coordinates N 59°16'09.48", E0P47'31.18" (Fig. 35). No cores.
Norwegian well 30/11-3 from 3207 to 3162 m, coordinates N 60°02'38.59", E 02°32'15.47" (Fig. 36). No cores.


In the Viking Graben, the formation is 208 m thick in the type well (25/5-1), 326 m in well 35/3-2 and 145 m in well 24/9-1. It is 45 m thick in well 30/11-3 on the western margin of the Horda Platform.


The Tryggvason Formation consists generally of mudstones with interbedded limestones. Interbedded sandstones are common in the Agat area. The content of limestones relative to mudstones is generally lower in the northern part of the Viking Graben (from blocks 30/2 and 30/3 northwards) than in the southern part. At the transition between the Viking Graben and the Horda Platform (e.g. block 30/11, Fig. 36) the formation consists of limestone. The mudstones are light to dark grey, often calcareous, occasionally micaceous, glauconitic and pyritic. The limestones are white to light grey or brownishgrey and argillaceous. The sand­stones are clear to light grey, very fine to fine grained and cemented by calcite.

Basal stratotype

The lower boundary is defined by a decrease in gamma-ray intensity and an increase in velocity from the Blodøks Formation into the Tryggvason Formation (Fig. 33 and 34). This is due to the difference in carbonate content.

Characteristics of the upper boundary

The upper boundary shows an increase in gamma-ray intensity and a decrease in velocity from the Tryggvason Formation upwards into the Kyrre Formation (Fig. 33). This log change is due to the lower carbonate content of the Kyrre Formation.


The formation is present in the Viking Graben and northern Tampen Spur area towards the Marulk Basin.

Occurrences of formation tops in wells


Early to Mid Turonian.

Depositional environment

Open marine.


The Tryggvason Formation is time-equivalent with the Herring Formation and the lower part of the Hod Formation in the central North Sea, and also with the informal "formation C" of Deegan & Scull (1977) (Fig. 6).

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