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Rødby Formation (Rødbyformasjonen)

(From NPD Bulletin no. 5)

Cromer Knoll Group


Named by Larsen (1966) after a town on the island of Lolland in southern Denmark.

Well type section

The Danish well Rødby-1 drilled on the island of Lolland (Larsen 1966).

Well reference sections

Norwegian well 2/11-1 from 2910 to 2887 m, coordinates N 56°14'16.98", E 03°27'07.05" (Fig. 12). No cores. Norwegian well 2/7-15 from 3419 to 3401 m, coordinates N 56°23'46.82", E 03°18'54.63" (Fig. 22). No cores.


In the well type section the thickness is 23 m. The thicknesses in the reference sections are 23 m in well 2/11-1 and 18 m in well 2/7-15. The formation generally ranges in thickness between 15 and 30 m. In the Viking Graben it may reach thicknesses of more than 200 m (Deegan & Scull 1977).


Mainly red-brown marlstones, but green and grey colours may occur. Glauconite and pyrite may be pre­sent. Sandstones and siltstones are known to be pre­sent locally.

Basal stratotype

The lower boundary is placed on the Sola and Åsgard Formations and the Ran sandstone units, and represents an upward decrease in gamma-ray response and usually an increase in velocity into the Rødby Formation (Figs. 12,22 and 23).

Characteristics of the upper boundary

The upper boundary can be seen as an upward decrease in gamma-ray response and a increase in velocity when going into the more calcareous sediments of the Svarte Formation (Figs. 33-36). On the Horda Platform the Rødby Formation is more calcareous and has a lower gamma-ray response and a higher velocity than the overlying unspecified unit of the Shetland Group (Fig. 37). Where the chalk facies of the Shetland Group is present, the upper boundary is characterised by a distinct upward drop in gamma-ray readings and a marked increase in velocity (Figs. 12, 15, 22-28)1


The formation is widespread in the North Sea, but are missing locally on the Utsira, Jæren and Mandal Highs, Tampen Spur and Horda Platform on the Norwegian sector.

Occurrences of formation tops in wells


The formation is of Albian age (locally Early Cenomanian in the Danish sector (Jensen et al. 1986)).

Depositional environment

The Rødby Formation was deposited as generally reddish sediments in an open marine, oxygenated environment with limited supply of clastics.

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