Sequence Stratigraphy - Trace Fossils as Indicators of Sedimentary Environments - page 167

intervals, contain abundant cemented (typically sideritic) horizons and nodules,
and commonly display cemented upper surfaces and erosion at the top,
attributed to development of the SU. The forced regressive shoreface consists
of well-developed, laminated to burrowed sandstones (BI

0-5) ( Fig. 4 A). The
laminated sandstones contain HCS and rare SCS consistent with storm deposi-
tion, with classical trace-fossil evidence of opportunistic recolonization and
their replacement by resident communities ( Pemberton and MacEachern,
1997 ). The forced regressive shoreface at Kaybob-Fox Creek reflects a moder-
ately storm-influenced shoreface succession ( MacEachern and Pemberton,
1992; Pemberton et al., 2012 ).
The Judy Creek Field, lying well to the northeast, contains the last (youn-
gest) forced regressive shoreface of the FSST, which is overlain by the lowstand
shoreface of the LST ( Figs. 5 and 6 ). The forced regressive shoreface is incised
into the marine mudstones of the underlying highstand parasequence, and like
the Kaybob-Fox Creek example, the RSME is demarcated by firmground omis-
sion suites attributable to the Glossifungites Ichnofacies (e.g., Spongeliomorpha
and firmground Thalassinoides ; Fig. 5 A and B). The incised shoreface is

¼

FIGURE 5 Incised shoreface deposits of the FSST. Core box photo (A) and close-up (B) from a
forced regressive incised shoreface in a seaward position. The forced regressive shoreface here rep-
resents the distal equivalent of the same falling stage systems tract (FSST) shown in Fig. 4 (see Fig. 3
for context). In this position, bioturbated silty mudstones interpreted as lower offshore deposits are
incised by the regressive surface of marine erosion (RSME), and overlain by moderately to intensely
bioturbated distal lower shoreface silty sandstones of the incised shoreface. The RSME is demar-
cated by firmground Spongeliomorpha ( S ) of the Glossifungites Ichnofacies. Core box photo (C) and
close-up (D) of the same lowstand shoreface, but lying in a more distal position. Here, the RSME has
passed into the basal surface of forced regression (BSFR), marked by upper offshore sandy mud-
stones of the regional parasequences sharply (but not erosionally) overlain by upper offshore
grit-bearing sandy mudstones of the forced regressive shoreface. Early Cretaceous Viking Forma-
tion, Judy Creek Field. See text for explanation. Scale bars ¼ 15 cm (A and C) and 3 cm (B).