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bioturbation, coupled with the ichnogenera pre-
sent, suggest an alternation between mainly sus-
pended-sediment settling and shifting-substrate
conditions under higher energy.
Facies association 1 (FA1): Lower
to middle shoreface
FA1 (Fig. 10) is predominantly sandy. Commonly,
this association shows an upward-sanding and
locally upward-coarsening, trend up to 5 m thick.
At the base, FA1 consists of intensely biotur-
bated (mixed
Cruziana
and
Skolithos
Ichnofacies)
to homogenised silty and very fine-grained sand-
stones (F6.4) that indicate lengthy periods (many
months) of low energy. The bioturbated sand-
stones are overlain locally by mixed sandstone/
mudstone wavy bedded combined-flow hetero-
lithics (F5.2.2). These basal deposits are sharply
overlain by low-angle laminated (HCS) very
fine-grained to fine-grained amalgamated (up to
3 m thick) sandstones (F4). Erosion surfaces are
common within the amalgamated sandy beds.
Thick amalgamated HCS beds in FA1 are inter-
preted as proximal storm beds. Sustained wave
motion during storms eroded any fair-weather
mud, with the exception of locally preserved
residual mud lenses and clasts. Local, weakly
laminated to homogeneous mudstones on top of
HCS-bearing event beds suggest resuspension of
the mud and the generation of high suspended-
sediment concentrations forming fluid muds.
Alternation of HCS beds and bioturbated sand-
stones indicates interruption of fair-weather
conditions by storms. The nature of the facies
(dominance of wave-generated structures) and
their sanding-up vertical arrangement, coupled
with the mixed trace-fossil assemblage showing
a proximal expression of the
Cruziana
Ichnofacies, suggest that deposition of FA1
occurred in a storm-influenced lower to middle
shoreface setting (cf. Walker & Plint, 1992;
Bhattacharya & Giosan, 2003). The local pres-
ence of combined-flow heterolithic deposits
might imply a nearby source of mud (i.e. transi-
tion into a delta-front setting).
Subfacies 6.5: Rooted sandstones
Bedding and internal lamination of the very fine-
grained to silty sandstone in this subfacies (up to
40 cm thick) are barely visible. The abundant to
complete bioturbation by vertical root structures
and small
Skolithos
and
Ophiomorpha
(Figs 8I & 8J),
together with the local presence of small organic-
matter lenses, suggest that Subfacies 6.5 represents
an immature palaeo-soil, developed in a relatively
low-energy setting with some salt-water influence.
Facies 7: Pinstriped-laminated mudstones
The pinstriped-laminated mudstone (Fig. 7F)
of Facies 7 represents the mud-dominated end
member (sandstone : mudstone ratios between
10 : 90 and 0 : 100) of the spectrum of heterolithic
deposits (Fig. 5). Facies 7 is interpreted to have
been deposited under relatively low-energy con-
ditions. Sand lenses (0.5 cm to 1.5 cm thick)
showing small-scale bi-directional ripple cross-
lamination indicate the presence of tidal cur-
rents. The predominance of pinstripe bedding
presumably results from the dominance of mud
over sand, indicating relatively low tidal veloci-
ties or a scarcity of sand. Bioturbation tends
to be sparse to uncommon and consists of
Chondrites
and rare
Planolites
, suggesting depo-
sition within highly stressed environments as a
result of either a high sedimentation rate or
reduced salinity.
FACIES ASSOCIATIONS AND
ENVIRONMENTAL INTERPRETATIONS
The common co-occurrence of certain facies
groupings, together with vertical changes in the
assemblage of deposit characteristics, allowed
the combination of closely and genetically
related facies into ten facies associations (Table 3)
that vary in their abundance through the Upper
Åre and Tilje formations. Using these facies asso-
ciations (FA), it was possible to deduce the com-
bination of processes that occurred and, hence,
the different sedimentary environments that
existed (Fig. 9).
Facies association (FA2): Transgressive
shelf lags
FA2 is overall sand-dominated and consists of tabu-
lar-stratified beds that are typically < 0.5 m thick, but
locally reach more than 1 m in thickness. This FA is
erosively based and consists of moderately to poorly
sorted fine-grained to medium-grained reddish
sandstone (F6.1) that displays a homogeneous
aspect due to the complete bioturbation. Vertical
burrows are large and diverse, displaying a proximal
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