Not Formation (Notformasjonen)
(From NPD Bulletin no. 4)
Fangst Group
Name
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.
Thickness
14.5 m in the type well and 37 m in the reference well.
Lithology
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.
Age
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.
Correlation
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.
