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• Pre-rift stage characterised by tabular/evenly
thick stratal units within each fault-block. The
thicknesses of these units may vary from block
to block due to differential subsidence.
• Proto-rift stage characterised by near-tabular
stratal units due to minor fault movements of
pre-existing faults.
• Early rift stage showing the following
char acteristics:
⚬
Early-stage scattered local depocentres;
⚬
Asymmetrical stratal units, typically shaped
as wedges (downflank) as a response to the
fault-block rotation;
⚬
Potential erosion, starvation or low deposi-
tion-rates at footwall crests, due to fault-block
rotation and isostasy-driven footwall uplift;
⚬
At the coast, the hangingwall areas show a
high palaeo-shoreline trajectory with an
aggradational style, whereas the footwall
areas have a low palaeo-shoreline trajectory
that reaches farther basinward;
⚬
Facies and lithological segregation within
rotating fault-blocks. The hangingwall area is
prone to show transgressive strata, whereas
footwall areas are dominated by progradational
events;
⚬
Occurrence of isolated fluvial channels in the
hangingwall area due to axial drainage being
steered into the subsiding areas;
⚬
Development of irregular coastline morphol-
ogy in terms of spit and embayments, due to
contrasting/asymmetric subsidence rates
along strike as the shoreline of the footwall
areas extends further into the basin compared
to the shoreline at the hangingwall areas;
• Main rift stage:
⚬
Enhanced stratal thickness development in
hangingwall and stratal wedge-shaped units
toward the footwall crest;
⚬
Development of footwall islands with erosion
of elevated areas;
⚬
Flooding of fault-blocks and landward retreat
of shoreline;
• Late rift (or transition to post-rift) stage:
⚬
Passive infill with parallel build-up and onlap
strata;
within the Brent Group with regard to the generic
pre-rift to syn-rift structural and infill models, as
listed above. This has been achieved by examina-
tion of four east-west profiles (Fig. 1), using a
combination of seismic, biostratigraphic and well
data. We discuss how the early stage of rifting can
be interpreted from the sedimentological response
to fault population and their influence on coastal
morphology.
GEOLOGICAL SETTING AND BASIN
HISTORY
Following the Permo-Triassic rift phase, the
Early Jurassic northern North Sea experienced
thermal subsidence along the inherited rift
topography (Gabrielsen
et al
., 1990; Odinsen
et al
., 2000a, b). This subsidence led to the
transgression (north-directed) of the fluvial-
dominated Statfjord Formation and a north-
south seaway was established through the
Viking Graben at approximately Sinemurian
time (Steel, 1993). The lower part of the Dunlin
Group (Sinemurian-Pliensbachian) encom-
passes the Amundsen and Burton formations,
which consist of shales and siltstones (Vollset &
Doré, 1984) deposited in a shelfal setting
(Husmo
et al
., 2003). The shallow marine Cook
Formation built out into this seaway from the
Norwegian mainland during Pliensbachian
time, in response to basin margin uplift and
erosion (Charnock
et al
., 2001; Folkestad
et al
.,
2012). Subsidence continued in the northern
North Sea, as the Cook Formation was draped
by offshore mudstones of the Drake Formation.
The overall thickness distribution of the Lower
Jurassic Statfjord Formation and the Dunlin
Group suggests that the future Viking Graben
was built on a broader, possibly asymmetric
basin (Færseth & Ravnås, 1998); a basin config-
uration inherited from the Permo-Triassic
stretching phase (Færseth, 1996).
The Oseberg and Broom formations have tradi-
tionally been included in the Brent Group but
they are not genetically linked to the other for-
mations of the group (Steel, 1993). The Broom
and the time-equivalent Oseberg formations
(Aalenian) represent coarse-grained fan deltas
that prograded into the basin from the uplifted
margins of the Viking Graben and are restricted to
the western (Broom Formation) and eastern
The aim of the study
The purpose of this paper is to describe and inter-
pret the stratal architecture of the Jurassic pack-
ages and depositional environment variability
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