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The more heterolithic examples of FA3 show
a  similar coarsening/sandier and thickening
upward organisation. Wavy-bedded mixed sand-
mud (F5.2.1 and F5.2.2) and mudstone-dominated
(F5.5) deposits showing current (bipolar) and
combined-flow ripples are commonly overlain by
thick fine-grained sand-dominated heterolithics
(F5.1). At the 10 cm to 30 cm scale, these hetero-
lithic deposits (F5.2.1 and F.2.2) contain a decimetre-
scale alternation between higher-energy deposits
(coarse-grained, abundant fluid-muds, bioturba-
tion uncommon, thicker bedded) and lower-energy
(fine-grained, more intensely bioturbated and
thinner bedded) that is interpreted as the result of
high-energy river floods that alternate with lower-
energy inter-flood sedimentation. These deposits
are commonly punctuated by upward-fining, cross-
bedded, medium-grained to fine-grained sandstones
(F2) that were deposited by relatively higher energy
unidirectional (river) currents.
The stacked coarsening/sandier upward sand and
mixed sand-mud dominated successions of FA3,
showing persistent current-generated structures con-
taining tidal indicators and mixed Cruziana-Skolithos
bioturbation assemblages, are interpreted to be depos-
ited in a tidally influenced outer distributary channel
to upper delta-front mouth-bar region. The local pres-
ence of oscillatory and combined-flow ripples and
HCS, suggest that mouth bars were also subjected to
episodic wave energy. The overall upward-fining
cross-bedded successions that punctuated the most
heterolithic mouth-bar deposits are interpreted as ter-
minal distributary channels (Olariu & Bhattacharya,
2006; Ichaso & Dalrymple, 2009), where cross bed-
ding was generated by the migration of dunes and
ripples. These deposits will be referred in the follow-
ing sections as sandy mouth-bars and channelised
mouth-bar successions, based on the absence or pres-
ence of terminal distributary channels, respectively.
100
To p
335
343
331
339
90
80
344
340
328
332
336
70
60
50
345
329
333
337
341
40
30
330
346
342
20
10
0
cm
Base
Fig. 10. Facies association FA1. Lower to middle shoreface
deposits are predominantly sandy and show intensely biotur-
bated sandstone overlain by low-angle laminated sandstone
interpreted as hummocky cross-stratification (HCS) forming
cleaning and sanding upward successions. Example taken
from reservoir zone Åre 3 (A3).
double mud drapes (F3). HCS beds (F4) are pre-
sent locally. The abundance of cross-bedding
indicates that currents dominated sedimentation.
The low degree and diversity of vertical trace fos-
sils, together with the preserved sedimentary
structures, suggest a relatively high-energy envi-
ronment with moderate to high sedimentation
rates, physical reworking and/or salinity
variations. The double mud drapes and bipolar
ripple cross-lamination indicate tidal influence
during deposition and the local presence of HCS
suggests sporadic storm/wave action. The clean-
ing, sandier-upward trends on the higher part of
the succession suggest that suspended-sediment
values were lower at higher levels in the water
column, whereas the stratigraphically lower
intervals show thicker mud (fluid muds) layers
suggesting deposition in lower levels within the
water column (cf. Dalrymple et al ., 2003).
Facies association 4 (FA4): Proximal to
medial tidally influenced delta front
FA4 (Fig.  13) is dominated by mixed sandstone-
mudstone heterolithics. These deposits are
comprised of stacked coarsening-upward and
thickening-upward successions (3 m to 5 m thick).
Commonly, sharp-based current-dominated het-
erolithics (F5.2.1) alternate with combined-flow
heterolithics (F5.2.2). Heterolithic units show
mixed Cruziana and Skolithos assemblages,
mostly showing deposit-feeder structures. These
deposits are generally overlain by  fine-grained
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