Hardråde Formation (Hardrådeformasjonen)

(From NPD Bulletin no. 5)

updated to follow: Stratigraphic Guide to the Cromer Knoll, Shetland and Chalk Groups of the North Sea and Norwegian Sea. Felix M. Gradstein & Colin C. Waters (editors), Mike Charnock, Dirk Munsterman,  Michelle Hollerbach, Harald Brunstad, Øyvind Hammer & Luis Vergara (contributors). Newsletter on Stratigraphy, vol 49/1 pp71-280, 2016

Shetland Group

Name

Named after Harald "Hardråde" Sigurdsson, a Norwegian King (A.D. 1046-1066).

Lithology

The formation consists generally of interbedded limestones and mudstones, except in the Troll area where it is thin and consists of a single limestone bed. The limestones are white or pale, moderately hard to very hard. The mudstones are medium to light grey, often silty and calcareous.

Thickness

The formation is 291 m thick in the type well (30/11-3) and 10 m in well 31/6-2. It is absent on tilted fault blocks in the Troll area (e.g. well 31/2-9).

Geographical Distribution

The formation is present on the Horda Platform (Figure 32b in Isaksen & Tonstad (1989)).

Type Well

Norwegian well 30/11-3 from 2892 to 2601 m, coordinates N 60°02'38.59", E 02°32'15.47" (Figure 36 in Isaksen & Tonstad (1989)). No cores.

Reference Well

Norwegian well 31/6-2 from 968 to 978 m, coordinates N 60°34'58.24", E 03°54'55.76" (Figure 37 in NPD Bulleton 5). Cored through the formation.

Upper and lower boundaries

Upper Boundary

The upper boundary is towards the Rogaland Group. When it is towards the Lista Formation it is characterised by an upward increase in gamma-ray intensity and a distinct drop in velocity due to a transition from limestones to mudstones (Figure 36 in Isaksen & Tonstad (1989)). An upper boundary towards the Våle Formation lacks the distinct drop in velocity. This is due to the presence of limestones and a more marly facies in the Våle Formation. An upper boundary towards the Ty Formation is shown by a change to sandstone.

Lower Boundary

The lower boundary is towards the Kyrre Formation or an unconformity above older rocks. The boundary towards the Kyrre Formation is identified by the absence of relatively thick limestone beds in this formation and a lower content of calcareous material in the mudstone. This results in a decrease in gamma-ray intensity and an increase in velocity from the Kyrre Formation into the Hardråde Formation (Figure 36 in Isaksen & Tonstad (1989)). The formation has an unconformable lower boundary in the Troll area.

Age

Late Campanian to Maastrichtian.

Correlation

The Hardråde Formation is time-equivalent with the Jorsalfare and Tor Formations of the Shetland Group (Figure 6 in Isaksen & Tonstad (1989)).

Depositional environment

Open marine.

 



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