Sequence Stratigraphy - Trace Fossils as Indicators of Sedimentary Environments - page 169

characterized by a coarsening-upward succession of bioturbated muddy to silty
sandstones with rare tempestites. Sediment grain sizes are significantly larger
than in the underlying highstand succession. Further seaward, the RSME passes
into the conformable BSFR, identified as the CC by MacEachern et al. (1999a)
following the three-systems tract model of Posamentier et al. (1988) . Figure 5 C
and D shows the BSFR at Judy Creek, where underlying upper offshore mud-
stones of the HST are overlain by similar upper offshore mudstones of the
FSST, with the exception that the upper mudstones contain coarser-grained
sand and dispersed granules of chert supplied during forced regression. Ichno-
logically, the two mudstones are identical, showing BI

5 and fully marine
suites attributable to a proximal expression of the Cruziana Ichnofacies. The
BSFR is preferentially preserved in this location, as it resides beyond the sea-
ward termination of the RSME.
The LST shoreface rests on the CC and progrades over the forced regressive
deposits ( Figs. 3 and 6 ). The lowstand shoreface corresponds to the seaward
limit of shoreface progradation in the area. It lies along the depositional strike
of the Viking Joarcam sand body, which has also been interpreted as a lowstand
shoreface ( Posamentier and Chamberlain, 1993 ). The CC at the base of the LST
has a subtle physical expression, marked by a decrease in the caliber of river-
borne sediment delivered to the sea following the onset of RSL rise. At Judy
Creek, it is expressed sedimentologically as the boundary separating a
coarsening-upward lowstand shoreface succession that is finer-grained than
the underlying forced regressive shoreface ( Fig. 6 A). In landward positions, flu-
vial topset deposits cap the lowstand shoreface succession ( Fig. 6 A). The upper
surface of the LST shoreface represents the MRS and is recognized by the tran-
sition from a coarsening-upward succession recording progradation and aggra-
dation of the shoreline to fining-upward successions recording transgression
( Fig. 6 ). When preserved from erosion by wave ravinement, the MRS is typi-
cally a conformable surface or a surface of non-deposition, depending on the
sediment supply conditions during the overlying TST ( Fig. 6 C and D). In land-
ward positions, the MRS may be reworked during transgressive wave ravine-
ment to form a composite surface designated as WRS/MRS ( Fig. 6 A and B).
Omission suites may be present at either expression of the MRS, but are
generally palimpsest softground suites. Where wave ravinement is pronounced
and where it cuts across compacted facies, firmground omission suites attributed
to the Glossifungites Ichnofacies may occur. Potentially, suites of the Teredolites
Ichnofacies may also occur where coastal swamp deposits were exhumed. Hard-
ground suites of the Trypanites Ichnofacies are not common in this scenario.

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3.1.2 Incised Shorefaces of the TST
The Viking Formation of Alberta contains a number of incised shoreface depo-
sits that directly overlie WRSs (e.g., MacEachern et al., 1999a,b; Pemberton
et al., 2004; Walker and Wiseman, 1995 ). An excellent example of this occurs