Sequence Stratigraphy - Trace Fossils as Indicators of Sedimentary Environments - page 171

also be expected, as well as palimpsest softground suites. In the Joffre area, the
WRS/SU of the Viking Formation is most commonly demarcated by firm-
ground Thalassinoides , Spongeliomorpha , and Diplocraterion , or palimpsest
softground suites consisting of Skolithos and Diplocraterion , depending upon
the consistency of the exhumed substrate ( Fig. 7A and B ).
The facies that comprise the transgressively incised shoreface successions in
the Viking Formation at Joffre are similar to those of the forced regressive com-
plexes and lowstand shorefaces. They form coarsening-upward successions that
contain fully marine trace-fossil suites attributable to the Zoophycos , Cruziana,
and Skolithos ichnofacies. Facies record pervasively bioturbated (BI

4-5)
silty mudstones, sandy mudstones, muddy sandstones, silty sandstones of the
lower offshore, upper offshore, lower shoreface, and middle shoreface, respec-
tively ( Fig. 7 ). Tempestites are locally intercalated, but constitute a minor com-
ponent, indicating a weakly storm-affected shoreface setting ( MacEachern and
Pemberton, 1992; Pemberton et al., 2012 ). The transgressively incised shore-
faces most closely resemble the forced regressive shorefaces, particularly in dis-
playing incision into underlying units. In more landward positions, where the
overlying facies record deposition above fair-weather wave base, the WRS/
SU appears similar to the RSME. Both discontinuities possess omission suites
dominated by the Glossifungites Ichnofacies. Commonly, however, the basal
discontinuity of the transgressively incised shoreface is mantled with a granule
to fine pebble lag (e.g., Fig. 7A and B ), indicating that sediment eroded during
transgression by the WRS is typically coarser than the sediment eroded
during forced regression by the RSME.
In contrast to the coarsening-upward forced regressive shoreface deposits,
transgressive shorefaces display overall retrogradational (fining-upward) stack-
ing trends that are easier to observe at the systems-tract scale. At the facies
scale, however, differentiating incised shorefaces of the TST from those of
the FSST can be challenging. TST shoreface successions tend to be thicker than
those of the FSST, because they display aggradation reflecting increasing
accommodation space.
In the FSST shorefaces, the omission suites related to the RSME are always
overlain by facies that record deposition above fair-weather wave base (i.e.,
lower shoreface deposits or shallower). By contrast, in the transgressive sce-
nario, the erosional WRS/SU may be overlain by facies that were deposited
below fair-weather wave base, because the surface was colonized as RSL con-
tinued to rise. Offshore silty and sandy mudstone deposits commonly overlie
thin transgressive lags and firmground omission suites associated with the
WRS ( Fig. 7C and D ; MacEachern et al., 1999a ). Additionally, omission suites
in the TST can record colonization under much lower energy conditions (e.g.,
upper or lower offshore) than in the FSST. Omission suites in offshore positions
are marked by a predominance of firmground Thalassinoides , Rhizocorallium,
and Zoophycos (e.g., MacEachern and Burton, 2000; MacEachern et al., 1999a ).
Careful analysis of the sedimentological and ichnological expressions of the

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