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syn-rift packages, with some indications that initial
rifting occurred concomitant with lowstand depo-
sition (12B to C) suggest a linkage with hinterland
uplift to the immediately succeeding rifting. it is
therefore speculated that the uplift of rift-margins
should be linked to, and is a manifestation of, basin-
scale structuring preceding and heralding the sub-
sequent mild rifting. However, the structuring of
the area was gentle and it is uncertain whether the
deeper seated faulting actually resulted in a faulted
topography at surface or if drape folding of the
supra-salt sediment pile was the dominant struc-
tural style during the Early and Middle Jurassic.
Proper wedge shaped packages are only locally
developed in the hanging-wall of some major basin-
bounding faults and only within certain strati-
graphic intervals, such as at the Åre to Tilje and
Tilje to Ror-Tofte transitions. in such settings a
faulted topography probably existed. More com-
monly, a gradual thinning into the faults is observed,
favouring a  more 'rounded' topography related to
drape folding (e.g. see Sharp et al ., 2000; see also
Withjack et al ., 1989; Corfield & Sharp, 2000
Corfield et al ., 2001; Marsh et al ., 2010). Moreover,
the megaseqeunces and their component segments
have an overall tabular appearance within a single
sub-basin, with thickness differences observed
only across major faults. in turn this suggests pre-
dominantly fault-related differential subsidence of
individual sub-basins. it is therefore problematic to
ascribe a proper syn-rift status to these Lower and
Middle Jurassic megasequences.
The regressive segment consists of a lower high-
stand normal regressive part, a forced regressive
part and a lowstand normal regressive part. The
lowstand normal regressive part often thickens
up  to form a thick forestepping aggradational
segment. Outbuilding was initially during an
interval of tectonic quiescence (the highstand nor-
mal regressive part) followed by an interval of
hinterland uplift and initial basinal rifting, which
resulted in the forced regressive and lowstand
normal regressive part.
The transgressive segments display greater varia-
bility in stratigraphic structure and internal sedi-
mentary architecture, formed in response to
increased rates of basinal subsidence and structur-
ing during relatively short-lived intervals with mild
rifting. The component higher-order sequences
nested within the transgressive segments, also
show large spatial variability in their (higher-order)
sequence development and structure, as well as in
stacking patterns.
Spatial and stratigraphic variability resulting
from the different combinations of subsidence/
uplift rates, sediment supply and calibre, basin
physiographies, component depositional systems
and their sediment dispersal are the rule, for
both a single as well as between the various mega-
sequences. This has resulted in relatively large
variability in sedimentary architecture of the
megasequences, despite their similar gross strati-
graphic structure. improved reservoir prediction
potential, both in terms of reservoir presence,
geometries, connectivities as well as reservoir
qualities, thus require a detailed knowledge of the
wide range of controlling factors responsible for
the resultant megasequence development.
Finally, the repeated occurrence and close
temporal linkage between hinterland uplift and
basinal rifting suggests a casual mechanism that
should be further investigated in refined struc-
tural models for rift-basin evolution.
CONCLUSIONS
On the Halten Terrace, the late Early to early
Middle Jurassic (late Sinemurian to Bajocian) was
a period of relative tectonic quiescence interrupted
by repeated intervals of mild rifting. Three second
order, regressive to transgressive, sequences, herein
referred to as megasequences, form the basin-fill
and display the following features: 1)  basal and
capping marine flooding intervals form the bound-
ing surfaces and 2) progradational  to retrograda-
tional stratigraphic architecture, normally with a
middle aggradational segment, representing the
outbuilding and retreat of predominantly basin-
marginal deltaic and estuarine systems.
Repeated outbuilding and retreat of basin-
marginal clastic wedges was primarily in response
to the interplay between sediment supply and the
background, tectonically induced, basin subsid-
ence and the linked hinterland-basin structuring.
ACKNOWLEDGEMENTS
This study reflects the work of a team of Shell
Exploration geologists and geophysicists working
over a period of several years on the Lower and
Middle Jurassic in Mid-Norway. The authors
thank colleagues and partners in joint ventures for
fruitful discussions over this period. We would
also like to thank R.J. Steel, H.D. Johnson and
A. Martinus for reviewing and suggesting improve-
ments to this paper.
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