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order) genetic sequences, composed in turn by a
lithosome stack of quite different architecture, i.e.
from normal through forced regressive through
aggradational to retrogradational. The lithosome
units nested within the various systems  tracts
define even higher order sequences, which  again
show variations in component facies tracts/deposi-
tional systems and strata architecture. Neglecting
that variability may arise when comparing
sequences at different hierarchical scales, from
contrasting basin settings or variable situations of
accommodation creation may have added to the of
the variety and misalignment of the alternative
approaches to sequence stratigraphy (see Catuneanu
et al ., 2009, 2010, 2011).
The aggradational segment, herein attributed to
the early transgressive systems tract, appears to be
a less common architectural element compared to
other systems tracts (Catuneanu et al ., 2009, 2011;
though see Van Wagoner et al ., 1990). This may
potentially reflect geologic setting; thick aggrada-
tional segments are often well-developed in sedi-
mentary cycles (megasequences) defining rift-basin
fills and especially those formed during late pre-
rift and inter-rift/early post-rift situations (Steel,
1993; Ravnås & Steel, 1998; Ravnås et al ., 2000).
During such conditions both subsidence and sedi-
ment supply rates are often high and potentially
near-balanced.
non-uniform relative sea-level fluctuations and
sedimentary response across the basin area.
The temporal and spatial changes in depositional
styles, sediment supply and accommodation crea-
tion reflect continuous minor and variable struc-
turing during the Early to Middle Jurassic. Repeated
rifting sustained the background subsidence and,
combined with eustatic sea-level changes, resulted
in a gradual drowning of the Norwegian-Greenland
Sea rift-system (Fig. 5), as well as repeated topogra-
phy rejuvenation and thereby changing basin
configurations and subsidence patterns of the
Halten Terrace area.
Repeated structuring of basin areas was argued
by Ravnås and co-workers (2000) as the main con-
trolling factor on the megasequence structure in
their study of time-equivalent marine rift-basin
infill of the northern North Sea. Steel (1993)
favoured hinterland uplift as the main controlling
factor on the formation of the sand-rich sandstones
forming the core of his 'post-rift megasequences'.
The same tectonostratigraphic controls are also
invoked for the Lower & Middle Jurassic infill of
the Mid-Norway 'inter-rift' or mild syn-rift condi-
tions. As such, these 'megasequences' mirror those
argued to be typical of combined 'inter-rift' to early
syn-rift origin in the northern North Sea (Steel,
1993; Ravnås et al ., 2000).
The falling-stage to lowstand system tract form-
ing the central sand-rich core of the megasequences
(Fig.  12A,B) reflects sea-level falls attributed to
repeated broad upwarping of the rift-margin and its
hinterland, similar to that proposed by Steel (1993)
for the northern North Sea equivalents. Thus hin-
terland structuring is favoured as the major control-
ling factor on the formation of the high-quality,
sheet-like or detached lowstand reservoir bodies,
whereas variations in the style and rate of basinal
structuring exerted the fundamental control on the
sedimentary architecture of the aggradational and
transgressive segments. The predictability of the
'transgressive' systems tract or segment develop-
ment and its stratigraphic architectures remain
challenging; also within the mild syn-rift infill
intervals (see also Ravnås & Steel, 1998; Gawthorpe
& Leeder, 2000; Ravnås et al ., 2000). However, some
general rules still apply, but careful calibration and
integration with the basin's structural history, basin
physiography and sediment yield potential of intra-
basinal highs is a pre-requisite in order to properly
assess and predict the reservoir architecture and
potential within these segments.
The stratigraphic occurrence of the lowstand
bodies immediately underneath the more typical
Major controls on gross sequence
architecture
The Lower to Middle Jurassic megasequences rep-
resent a series of depositional systems of varied
size, origin and provenance. Also, the basinal sub-
sidence and stretching (rifting) rates varied spa-
tially and temporarily during deposition of a
single megasequence and exerted an additional
fundamental control on the megasequence struc-
ture and sedimentary architecture (Fig. 12B to C),
as well as on basin physiography (see also discus-
sion in Yoshida et al ., 2007). in addition, the
larger-scale variations in background subsidence
and sediment supply (Fig.  3), with an overall
reduction throughout the Early and Middle
Jurassic, coupled with temporal changes in sedi-
ment calibre, had an additional impact on the
resultant 'syn-rift' infill. These longer and shorter
term temporal changes in basinal subsidence and
sediment supply rates resulted in the differences
in internal sedimentary architecture between the
Lower and Middle Jurassic megasequences.
Eustatic signals seem subordinate due to the
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