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Jorsalfare Formation (new) (Jorsalfareformasjonen)

(From NPD Bulletin no. 5)

Shetland Group


Named after Sigurd "Jorsalfare" Magnusson, a Norwegian king (A.D. 1103-1130).

Well type section

Norwegian well 25/1-1 from 2997 to 2711 m, coordinates N 59°53'17.40", E 02°04'42.70" (Fig. 33). One core (17 m) in the middle of the formation and another (4 m) at the base.

Well reference sections

Norwegian well 35/3-2 from 1665 to 1520 m, coordinates N 61°51'05.98", E 03°AG2%.2T (Fig. 34). No cores.
Norwegian well 24/9-1 from 3117 to 2752 m, coordinates N 59°16'09.48", E 01°47'31.18" (Fig. 35). No cores.


The formation is 286 m thick in the type well (25/1-1), 145 m in well 35/3-2 and 365 m in well 24/9-1.


The formation generally consists of mudstones interbedded with thin limestone beds. The mudstones are light to medium grey, often calcareous. The limestones are white to light grey, fine grained, occasionally sandy and dolomitic.

Basal stratotype

The lower boundary is defined by a decrease in gamma-ray intensity and an increase in velocity, reflecting an increase in calcareous content from the Kyrre Formation into the Jorsalfare Formation (Figs. 33 and 34). In the Tampen Spur area, however, the boundary may be difficult to identify due to small differences in calcareous content. The lower boundary may be unconformable above the Jurassic sequences (e.g. in the Gullfaks area).

Characteristics of the upper boundary

The upper boundary may be towards the Våle, Lista or Ty Formations of the Rogaland Group. When the upper boundary is towards the shale of the Lista Formation it is usually characterised by an upward increase in gamma-ray intensity and a distinct drop in velocity (Fig. 34). When it is towards the Våle Formation it does not show the same distinct drop in velocity and increase in gamma-ray intensity, because the overlying lithology consists of limestones or calcareous mudstones (Fig. 35). Where the upper boundary is towards the Ty Formation it is identified as a change to sandstone (Fig. 33).


The formation is present in the Viking Graben and on the Tampen Spur. Its boundaries towards the Jorsalfare Formation in the Viking Graben, the Hardråde Formation on the Horda Platform and the Tor Formation on the Utsira High are illustrated in Fig. 32b.

The main characteristics that can be used to distinguish the three formations are:
a. The Jorsalfare Formation contains shales with thin limestone beds which are usually no thicker than 5 m.
b. The Tor Formation is dominated by limestones, and has a negligible shale content.
c. The Hardråde Formation contains thick limestone beds (10-60 m), as well as shales, except in the Troll area where it is thin and may consist of only a single bed of limestone or marly limestone. Separation of these three formations may be difficult in transitional areas.

Occurrences of formation tops in wells


Late Campanian to Maastrichtian.

Depositional environment

Open marine.


Hardråde and Tor Formations of the Shetland Group, and also with the informal "formation E" of Deegan & Scull (1977) (Fig. 6).

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