Ile Formation (Ileformasjonen)

(From NPD Bulletin no. 4)

Fangst Group


From the Norwegian word for a stone sinker or a drag. The unit corresponds to the lower part of the informal Tomma formation (Hl-4) or "Tomma III".

Well type section

Well 6507/11-3 (Saga Petroleum), coordinates 65°01'59.8"N, 07°30'42.34"E, from 2536 m to 2471.5 m (Fig. 16). The entire formation is cored except for the basal 2 m.

Well reference section

Well 6407/1-3 (Statoil), coordinates 64°52'25.48"N, 07°02'53.47"E, from 3813 m to 3741 m (Fig. 19). One core (10 m recovery), from the upper part of the unit.


64.5 m in the type well and 72 m in the reference well.


Fine to medium and occasionally coarsegrained sandstones with varying sorting are interbedded with thinly laminated siltstones and shales. Mica-rich intervals are common. Thin carbonate-cemented stringers occur, particularly in the lower parts of the unit.

Basal Stratotype

The lower boundary is defined at the base of a generally upwards coarsening sequence visible on the gamma ray log. In wells where this coarsening trend is not evident on logs, the base of the formation may be picked where the overall lithology changes from siltstone to sandstone. Often this transition is associated of one or more carbonate-rich beds.


Late Toarcian to Aalenian.

Depositional environment

The formation represents various tidal-influenced delta or coastline settings.

Lateral extent and variation

The Ile Formation generally varies from 50 m to 100 m over most of Haltenbanken, with a general thickening to the west and a marked thinning to the northeast. It is also encountered in wells on Trænabanken. Sandstone-dominated successions of similar age have been located by sea bottom sampling and shallow drilling on the eastern part of the Trøndelag Platform. (Bugge et al. 1984).


No distinct comparable time equivalent formations are known from the North Sea area. In the Hammerfest Basin the middle part of the Stø Formation may be correlated to the Ile Formation.

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