Not Formation (Notformasjonen)

(From NPD Bulletin no. 4)

Fangst Group


From the Norwegian word for a sweep net. The unit corresponds to the middle part of the informal Tomma formation (Hl-4), or "Tomma II".

Well type section

Well 6507/11-3 (Saga Petroleum), coordinates 65°01'59.8"N, 07°30'42.34"E, from 2471.5 m to 2457 m (Fig. 16). The entire unit is cored, including the base.

Well reference section

Well 6407/1-3 (Statoil), coordinates 64°52'25.48"N, 07°02'53.47"E, from 3741 m to 3704 m (Fig. 20). One core, 10 m recovery, including the top.


14.5 m in the type well and 37 m in the reference well.


Claystones with micronodular pyrite coarsen upwards into bioturbated fine-grained sandstones which are locally micra-rich and carbonate cemented.

Basal Stratotype

The lower boundary is defined by an abrupt increase to a steady high gamma ray response. In the type well this occurs immediately above a thin matrix-supported conglomerate.


Aalenian to Bajocian.

Depositional environment

The basal part of the formation reflects a semi-regional transgression which led to the development of lagoons or sheltered bays. The upper part of the unit consists of prograding deltaic or coastal front sediments.

Lateral extent and variation

The formation is recognized over the entire Haltenbanken area, if not eroded. The thickest development (<50 m) is seen on the southwestern part of the Halten Terrace and the unit generally thins eastwards on the Trøndelag Platform. On Trænabanken a time equivalent succession dominated by mudstone is assigned to the Viking Group.


In the Hammerfest Basin the middle part of the Stø Formation is thought to correlate with the Not Formation. No similar unit is recognized in the North Sea.

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