Fangst Group (Fangstgruppen)
(From NPD Bulletin no. 4)
Name
Norwegian name for catch. Previous informal name was the Tomma formation
(Hl-4).
Type area
The Halten Terrace. The group's development is illustrated by the type
section of its basal unit in well
6507/11-3
(Saga Petroleum), coordinates
65°01'59.8"N, 07°30'42.34"E, from 2536 m to 2412 m (Fig. 16). Reference
wells for the group are
6407/1-2
(Statoil), coordinates 64°47'50.61"N,
07°02'23.76"E, from 3907 m to 3658.5 m (Fig. 17), and
6507/12-1
(Saga Petroleum), coordinates 65°07'01.62"N, 07°42'42.61"E, from 2213 m to 2094
m (Fig. 18).
Lithology
The Fangst Group typically comprises three li-thological units: a lower
fine to medium-grained sandstone with numerous shaly interbeds, a middle
mudstone, and an upper relatively massive fine to coarse-grained
sandstone. Each of these units are defined as formations herein.
Basal Stratotype
The base of the group is defined by the base of
the Ile Formation as described below.
Lateral extent and variation
The Fangst Group is represented in most of the Trænabanken - Haltenbanken
area except on the highest parts of the Nordland Ridge where its
constituent units have been eroded. Time-equivalent sandstone-dominated
sequences subcrop on the sea-floor along the inner part of the Trøndelag
Platform (Bugge et al. 1984) and outliers of Middle Jurassic sediments are
present east of the Froan islands and beneath Beitstadfjorden in
Trøndelag. The latter probably represent a continental facies equivalent
to the dominantly marine Fangst Group.
Along the southern margin of the Nordland Ridge (e.g. the Heidrun Field)
the succession is much thinner than on Halten Terrace and the threefold
lithologic division is not so obvious. Further north the Trænabanken
wells show a lateral facies change to marine mud-stone of the
Viking Group
and only the lower unit of the Fangst Group (the
Ile Formation) is recognized.
Occurrences of group tops in wells
Isochore map BÅT-FANGST
Age
Late Toarcian to Bathonian.
Depositional environment
Shallow marine to coastal/deltaic facies dominate sequences on the Halten
Terrace. Increasing continental influence is inferred towards the
Trøndelag Platform to the east, especially in the lower part of the group.
Upper parts interfinger with marine shales to the northeast in the
Trænabanken area.
Correlation
The Fangst Group corresponds generally to the Brent Group in the North Sea
and to the Stø Formation on Tromsøflaket. However, the basal part of Stø
Formation is older and the base of the Brent Group is slightly younger
than the Fangst Group.
Subdivision
Although three formations are described herein it is clear that increasing
knowledge will lead to the establishment of a more varied framework to
reflect the lateral facies changes seen in the area.
Ile Formation
Not Formation
Garn Formation
