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Well 7226/11-1 (Norsel High)
with fine-grained units and thin coal beds.
Sandstone units are typically sharply based
(Fig. 11A) and are associated with eroded organic
debris, mudstone clasts and siderite nodules.
These lags are usually succeeded by cross-stratified
sandstones. As shown in Fig. 11B, weakly tangen-
tial set bases and micaceous/organic drapes on
fore-set lamina can be seen in some individual
sets, but these are not pervasive through the facies
units. Finer grained sandstone capping the fining
upwards units (Fig. 11C) show predominant sub-
horizontal lamination with current ripples and are
occasionally bioturbated, although not very inten-
sively. The associated fine-grained strata are invar-
iably grey and comprise laminated mudrocks,
thin-bedded sandstone and thin coal beds with
preserved carbonaceous rootlets (Fig. 11D).
In well 7121/4-F-2H the upper part (app. 35 m)
of the Tubåen Formation (above ~2720 m in Fig. 10)
shows a distinct coarsening upwards (CU) grain
size motif. The lower part of this CU-unit is in par-
ticular characterised by very fine-grained to fine-
grained micaceous sandstones with abundant cm
to dm scale wave-ripple lamination (e.g. Fig. 11E)
and discrete event beds with internal low-angle
cross-stratification (Fig.  11F). These strata pass
vertically into coarser grained sandstones and
eventually to a sharply based fining upwards unit
dominated by dm-scale cross-stratification (Fig. 10).
As annotated in Fig. 10, the cored section can be
related to deposition in a variety of terrestrial to
marginal marine environments, however with
increasing marine impact towards the top. Similar
to other interpreted sections (Figs  8 and 9),
the  major fining upwards sandstone bodies are
related to deposition within fluvial channels,
however with the observed bioturbation and cross-
stratification (tangential set bases and possible
drapes) indicating some more marine impact to
the west, with possible tidal modulation of bed-
forms within the channels. The interbedded fine-
grained material and thin coal beds are related to
deposition and peat accretion (coal) in lakes and
swamps of the surrounding delta plain. A minor
sandy fining upwards unit is also related to depo-
sition in a possible crevasse channel (Fig.  10).
Channel sandstone deposits in the lower to mid-
dle part of the Tubåen Formation account for
approximately 78% of the terrestrial interval in
well 7121/4-F-2H. The relatively high channelised
deposits content is generally indicative of good
lateral connectivity between sandstone bodies
(cf. Bridge & Mackey, 1993).
The Tubåen Formation is 34 m thick in well
7226/11-1 (Fig.  9, cored section above app.
1233 m) and is more or less completely sandstone-
dominated, akin to the section in well 7124/3-1.
As illustrated (Fig. 9), the formation can be divided
into a series of sharply based fining upwards
units, ranging in thickness from approximately
3 m and up to 10 m. The coarsest material consists
of rounded quartzite clasts with long axes up to
10 cm and the sandstones also contain abundant
eroded coal fragments and muddy intra-clasts.
Furthermore, the primary structures include strat-
ified, gravelly, sandstone and dm-scale cross-
stratified sandstone, with current ripples and
horizontal laminations in the upper parts of each
unit. Finer-grained intervals occur in the upper
part of the cored section, comprising laminated
very fine-grained sandstones and siltstones, occa-
sionally with preserved carbonaceous roots.
A high-energy fluvial setting is inferred for the
Tubåen Formation in well 7226/11-1. Particularly,
the coarse-grained nature of the sandstones and
the dominance of traction-generated sedimentary
features, such as cross-stratification and horizon-
tal lamination, may indicate a braided fluvial style
(as in well 7124/3-1). The preserved finer material
is related to events of channel abandonment and/
or the establishment of plant cover (palaeosol in
Fig. 9) in poorly preserved, associated floodplain
deposits.
Well 7121/4-F-2H (Hammerfest Basin)
Fig. 10 summarises the stratigraphy and sedimen-
tology of the Tubåen and lowermost Nordmela for-
mations in the central part of the Hammerfest
Basin. Here, the Tubåen Formation shows a thick-
ness of 121.5 m, of which approximately 110 m are
covered by the core. As in other wells, the basal
contact with the Fruholmen Formation is marked
by an abrupt increase in sandstone content,
although a stratigraphically more complete transi-
tion is observed from biostratigraphy (e.g. com-
pared to well 7226/11-1; Fig. 9), with inclusion of
Rhaetian strata in the lowermost part of the forma-
tion. The upper contact with the Nordmela
Formation is marked by a rapid transition into
finer-grained sandstones and siltstones.
Below approximately 2720 m (Fig. 10), stacked
sandstone units with predominant fining upwards
grain size motifs dominate, and are associated
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