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megasequences). This is attributed to the gross dep-
ositional setting (Fig. 4); initial uplift or broadening
of the intra-basinal highs during peak progradation
resulted in narrowing of the tectonically silled sub-
basins, then connected by a network of narrow and
shallow straits. This repeated basinal topography
rejuvenation caused changes into semi-protected
bays and tectonic estuaries where wave energy was
dampened and current activity enhanced (see
review in Reynaud & Dalrymple (2012) and refer-
ences therein).
more structured basin subject to spatial variations
in tectonically induced subsidence and uplift rates.
Variations in subsidence rates and sediment
supply/calibre has resulted in clear differences
between the megasequences; the aggradational
segment of the Tilje and Tofte-ile megasequences
is comprised by a distinct and layered aggrada-
tional stack of mixed-lithology (heterolithic)
fluviodeltaics and estuarine facies tracts. The
aggradational segment of the Garn megasequence,
in contrast, forms a sand-rich unit of amalgamated
sandy fluviodeltaic and estuarine facies tracts.
However, also in this megasequence, the strati-
graphic facies partitioning allows distinction
of superposed or stacked higher-order sandy
fluviodeltaic-to-estuarine units.
Sedimentary architecture of the aggradational
segment
The aggradational segment forms a relatively
thick stack of mixed wave- and tide-influenced
fluviodeltaic-estuarine lithosomes. These
formed during repeated advances of the basin-
marginal deltas and shorelines supplemented by
a steadily increasing supply from intrabasinal
sourced depositional systems (Fig. 12C) and
resulted in infilling of the broader, tidally modi-
fied embayments. During higher-order delta
retreats or avulsions, the former site of deltaic
deposition changed into estuaries, either as a
change from a distributary channel to a 'mini-
estuary' on a larger delta top or a change of the
structurally defined sub-basins into a 'tectonic
estuary' or bay. in either case, the prevalent wave
influence suggests a predominance of wave-
dominated rather than proper tide-dominated
estuaries.
The aggradational stacking is attributed to
increased rates of basinal subsidence rates. in par-
allel there was a renewed or increased sediment
supply from local intrabasinal sources such as
uplifted structural highs, i.e. horst and footwalls
along basin-bounding and sub-basin-bounding
masterfaults, to form locally developed prograding
depositional systems (Figs 12C & 14). These formed
a series of lateral (transverse), point-sourced sys-
tems which in some megasequences (Tilje and
Garn) linked with the larger axial or longitudinal
systems, whereas in others (Tofte-ile) joined later-
ally to form an elongate coastal/delta plain sur-
rounding the emerging highs. Entry points into
basinal areas were at cross-cutting faults and down-
dip of relay zones (e.g. Quin
et al
., 2010).
Unconformities are present across the most promi-
nent structural highs, where they form isolate
unconformity strands or merge to form a composite
unconformity. in consort, this suggests a return to a
Sedimentary architecture of the transgressive
segment
The transgressive segment commonly shows larger
infill variability, both between the various megas-
equences, as well as laterally and stratigraphically
within a single megasequence (Figs 12C and 14).
Basin-marginal depositional systems form an over-
all retrogradational or offset backstepping stacking
pattern, again composed of stacked, mixed tide-
and wave-structured fluviodeltaic lithosomes but
now with a clearer tidal signature (compared to
the underlying aggradational part). These represent
bay-fills with bay-head deltas and infills of wave-
dominated to tide-dominated tectonic estuaries
defined by individual sub-basins or half-grabens
(Tilje and Garn Formations) or a large (basin-wide),
partly segmented estuary or embayment (ile
Formation) (Fig. 14).
Sediment supply from local intrabasinal
sources, i.e. structural highs along basin-bounding
and sub-basin-bounding masterfaults, continued
but now as more locally developed depositional
systems (Fig. 12C). Braidplains formed along
larger and higher-relief intrabasinal highs and
sourced smaller and isolate deltas downdip on the
structures, whereas short-lived local shorelines
formed along smaller and lower relief emergent
islands, before these were drowned to form sub-
merged highs. Along the more prominent intra-
basinal highs there is often spatial variability in
delta types dependent on 1) sediment calibre,
resulting in the formation of normal river to braid-
plain deltas to fan deltas and 2) the local basinal
energy regime, with the resultant delta types
varying from river to wave to tidally influenced or
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