Environmental Engineering Reference
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FIGURE 5
Stratigraphic application of trace fossils in estuaries (left is oceanward and right is
landward). The uppermost panel shows a schematic interpretation of a transgressively filled estuary.
This differs from the models presented by
Dalrymple et al. (1992)
and
Martinius and Van den Berg
(2011)
in that it specifically recognizes bioturbated IHS belts and assigns them to the inner estuary.
The schematic model also attempts to encapsulate a backstepping stratigraphic framework. Genetic
stratigraphic units are bound by red lines (TS/SU) and six phases of transgression are shown (num-
bered 1 through 6 with blue markers on left of schematic). Unit 1 is fluvial. Units 2 and 3 are estu-
arine. Units 4-6 are shoreface through to offshore. The facies backstep and so the middle estuary
zone is labeled in phases 2 and 3 for reference. Images (A) through (M) are indicated in their sche-
matic position by their letter on the black circles. (A)
Gastrochaenolites
(
Ga
) at the base of a chan-
nelized Pleistocene TS/SU (Coos Bay, Oregon, USA). (B)
Thalassinoides
(
Th
) at the base of a tidal
channel (Pleistocene, Willapa Bay, Washington, USA). (C)
Thalassinoides
(
Th
) at the base of a
shoreface-associated marine flooding surface (WRS/SU) (Centenario Formation, Cretaceous,
Argentina). (D) Proximal offshore characterized by hummocky cross-stratification (HCS),
Astero-
soma
(
As
),
Diplocraterion
(
Di
),
Thalassinoides
(
Th
) and
Chondrites
(
Ch
) (Clearwater Formation,
Cretaceous, Alberta, Canada). (E) Offshore characterized by HCS,
Asterosoma
(
As
),
Planolites
(
Pl
), and
Chondrites
(
Ch
) (Jurassic, Germany). (F) Distal offshore characterized by
Nereites
(
Ne
) (Jurassic, Germany). (G)
Siphonichnus
(
Si
) with small-scale HCS, interpreted as shoreface
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