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tide-dominated, heterolithic deposits. These depos-
its are commonly punctuated by metre-scale fining-
upward, medium-grained, cross-bedded sandstones,
interpreted as terminal distributary channels.
Bioturbation within the mouth bars is moderate and
wave-generated structures are locally present. They
also record seasonal cyclicity in river discharge (cf.
Ichaso & Dalrymple, 2009) in the form of regular
variations in grain size, bioturbation and mud-layer
thickness, as was also present in the middle Tilje (T2
to T3.1). The mouth bars display lateral facies transi-
tions from sand-dominated in the NW-central areas,
to mixed sandstone-mudstone deposits toward the
SW (Fig. 22A). This variation, coupled with the
overall south-westerly decrease of the sand grain
size and the increase of the mudstone ratios
and bioturbation diversity, suggest an overall N to
SW proximal-to-distal transition. The distributary
mouth bars commonly alternate or change laterally
into thick, medium-grained to fine-grained, stacked,
tidal-fluvial channel deposits (FA8), which show
similar characteristics to the T3.2 and T4 channel
fills. Channel lags are locally present in the central
part of the field (Fig. 22A).
These deposits pass upward into the T5.2 reser-
voir zone, which is composed of tidal-fluvial chan-
nels (FA8), heterolithic distributary-mouth bars
(FA3) and storm-influenced delta-front (FA6) suc-
cessions. This upward shift to somewhat more dis-
tal deposits indicates the presence of a high-order
flooding surface at the base of T5.2. The thickness
of this zone varies between 10 m in the central area
to 15 m towards the SW, E and NE (Fig. 19).
Vertically staked, fining-upward, tidal-fluvial
channels (FA8) showing large
Diplocraterion
and
Skolithos
burrows are less common than in the
lower stratigraphic intervals. However, they occur
locally towards the north and central parts of the
field (Fig. 22B), where conglomeratic channel lags
and thick fluid-mud layers are present. These
deposits change towards the SW into moderatly
bioturbated distributary-mouth bars (FA3) and
towards the NE and E into storm-influenced delta-
front (FA6) deposits (Fig. 22B) showing thick (up to
40 cm) sharp-based large-scale HCS beds.
Locally towards the E, a few coarse channel fills
are abruptly overlain by thick, laminated mud-
stones, bioturbated sandstones and HCS beds,
suggesting the abandonment of the channels and
filling by low-energy marine processes followed
by episodic storms. Distributary channels or inter-
bar tidal-fluvial channels appear to be absent in
the NE region. In general, this facies distribution
suggests that the western margin of the field
(Fig. 22B) was dominated by more proximal tidal-
fluvial environments, whereas the eastern margin
of the field was subjected to more open- to mar-
ginal-marine wave and tidal processes.
The uppermost T6 reservoir zone is character-
ised by the dominance of wave-dominated and
tide-dominated delta-front deposits (FA4 and FA7
respectively) and distributary-mouth bars (FA3)
showing channelisation. The thickness of this
unit varies between 10 m and 20 m, with the great-
est thicknesses (20 m) localised in the north-cen-
tral part of the field (Fig. 19, cross sections I and
III). Well and core-log correlation panels suggest
that the base of T6 truncates the top of T5.2 locally
(Fig. 19, cross section III) in the central and SW
parts of the field, implying the filling of subtle
incision into T5. A lag (FA2) was not recognised at
the base of this unit.
Distributary-mouth bar deposits of T6, showing
abundant tidal and combined-flow structures
and moderate to intense bioturbation of mixed
Cruziana-Skolithos
ichnofacies, are locally punc-
tuated by sharp and erosively based tidal-fluvial
terminal distributary-channel deposits (up to
1 m thick). More proximal, fine and medium-
grained, sand-dominated heterolithic mouth bars
and the abundance of channel-fill deposits seem
to be concentrated in the central part of the field
(Fig. 22C). Terminal distributary channels (up to
80 cm thick) are also present towards the SW,
where medial mouth bars become muddier and
more bioturbated. Tidally influenced mouth bars
change laterally towards the E and NE into more
distal, laminated and tide-wave influenced delta-
front (FA4 and FA7) deposits lacking channels
(Fig. 22C). This unit should be regarded as the
first indicator of a later flooding event, as it marks
transitional or precursor facies to the fully marine
facies of the Ror Formation.
Lower Ror Fm.
The top of the Tilje Fm. (top of reservoir zone T6) is
defined by the abrupt transition from tide and wave-
influenced, channelised mouth-bar (FA3) and
delta-front deposits (FA4 and FA7) into thinly lami-
nated and intensely bioturbated marine mudstones
and silty bioturbated sandstones of the Ror Fm
(Fig. 22D). The contact between the Tilje and Ror
formations is defined at the regionally extensive,
abrupt transition from low to high readings in the
GR/RES-log, coupled with the change in DEN/NEU
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