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(A)
(B)
(F)
(G)
(C)
(D)
(E)
(H)
Fig. 4.
Conglomerate and sandstone facies in the
Smørbukk area. Dark scale bar adjacent to each
photo is 10 cm long. Facies 1: (A) Inversely graded
paraconglomerate; (B) Matrix supported conglomer-
ate, overlain by a structureless fluid-mud layer.
Facies 2: (C) Cross-bedded coarse-grained to
medium-grained sandstone showing 2 cm thick
organic-rich mud layers in the bottomsets that are
interpreted to be fluid-mud deposits; (D) Cross-
bedded medium-grained to fine-grained sandstone
showing basal flat to rounded rip-up mud clasts and
thin mud layers; (E) Cross-bedded medium-grained
to fine-grained sandstone showing thick basal fluid-
mud deposits and fluid-mud rip-up clasts. Facies 3:
(F) Ripple cross-laminated sandstone showing
bidirectional palaeocurrent indicators. Facies 4: (G)
Low-angle parallel-laminated fine-grained to very
fine-grained sandstone (HCS) capped by wave-
generated fluid-mud layer. (H) Thick-bedded, low-
angle, laminated, very fine grained sandstone (HCS)
showing internal truncations.
Rippled sandstone beds (up to 40 cm thick) show
a sparse, low-diversity, trace-fossil assemblage
mainly composed of small
Skolithos
and, rarely,
Planolites
, suggesting brackish-water conditions.
0.5 cm to 3 cm thick wave-generated fluid-mud
deposits (cf. Traykovski
et al
., 2000) are present
and commonly cap HCS beds. Fluid-mud layers
can be distinguished from those that accumulated
by slow settling over long periods of time by the
absence of distinct lamination and bioturbation,
except for post-depositional, top-down colonisa-
tion dominated by a low-diversity trace-fossil
assemblage composed of large-scale
Diplocraterion,
Skolithos
and rare
Planolites
(Ichaso & Dalrymple,
2009). Less commonly, vertical to sub-vertical
Glossifungites
are present at the top of the amalga-
mated HCS beds.
Facies 4: Hummocky cross-stratified
(HCS) sandstone
The amalgamated (up to 4 m thick) fine-grained
sandstone beds and bedsets of Facies 4 (Figs 4G &
4H) show pervasive hummocky cross stratification
(HCS) and are interpreted to be deposited under
high-energy oscillatory currents associated with
large storm waves (Hunter & Clifton, 1982; Klein &
Marsaglia, 1987; Duke
et al
., 1991; Yang
et al
.,
2006). Wave ripples occur immediately on top of
the HCS beds in many instances but the presence of
combined-flow ripples in some cases indicates that
there was a unidirectional component to the water
motion, due either to wind-driven residual motion
Facies 5: Heterolithics
Facies 5 (see also Table 2) consists of heterolithic
deposits composed of alternating sandstone and
mudstone with sand : mud ratios between 90 : 10
and 10 : 90. This heterogeneous facies displays
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