Environmental Engineering Reference
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reliefs, and bilobed burrows/trails) is useful for distinguishing emergent
channel-bar tops or the margins of floodbasin ponds. It is recommended that
tetrapod tracks are not considered as a key component of the Scoyenia Ichno-
facies; instead they are better compared with a tetrapod ichnofacies. The Mer-
mia Ichnofacies (simple horizontal trails, vertebrate swim traces), and probably
also the Characichnos Ichnofacies (tetrapod swim traces) are typical of flood-
basin ponds. Other analogous ichnocoenosis that also contain swim traces but
are restricted to subaqueous lotic settings (permanent channels) are the Chelo-
nipus and Hatcherichnus ichnocoenoses.
The identification of chambers and chambered trace fossils (commonly as
dominant components) is indicative of the presence of the Coprinisphaera ,
Celliforma , and Termitichnus ichnofacies, which were developed in soils sup-
porting different plant communities (herbaceous, scrubs and woodlands, and
closed forests, respectively). Several trace-fossil assemblages from paleosols
developed in fluvial deposits that lack insect trace fossils cannot be included
at present in existing ichnofacies. However, a group of these assemblages is
characterized by large burrows of vertebrate origin that occur in well-drained
calcareous paleosols, and another group of assemblages is typified by burrows
or chambers of possible crayfish origin in paleosols with fluctuating water table.
Furthermore, the potential rhizolith ichnofacies, dominated by root traces, is
recurrent enough and can yield significant paleoenvironmental inferences to
be considered as a tempting idea to explore.
The Skolithos Ichnofacies (simple vertical burrows and J, or U-shaped ver-
tical burrows) is related with the top of fluvial bars, although the subaerial or
subaqueous nature of the trace fossils must be confirmed in each case. If related
with subaerial exposure of fluvial bars, it may mark interruptions in fluvial
channel discharge or low flow-regime conditions. The Grallator (bird tracks,
bipedal tri- or tetradactyl tracks with thick digits) and Batrachichnus ichno-
facies (Q 4/5, Q 5/5 sl, Q 5/5 st, and chirotheriid tracks) appear on top of channel
bars, crevasse splays, and margins of floodbasin ponds.
A major challenge in continental ichnology is the agreement upon a unified
ichnofacies scheme that would be able to integrate invertebrate, vertebrate, and
plant trace fossils. Alternatively, it is possible that a consensus will never be
reached and tetrapod ichnofacies will consolidate as a separate and parallel
scheme to archetypal invertebrate ichnofacies.
One of the major contributions of the ichnofacies analysis to the paleoenvi-
ronmental interpretation of fluvial successions is the recognition of composite
or mixed assemblages that contain significant participation of two ichnofacies.
These composite ichnofacies (e.g., Mermia - Scoyenia , Scoyenia - Celliforma )
holds the potential of reflecting subtle environmental changes that commonly
cannot be inferred from physical sedimentary structures alone. Vertical replace-
ment of ichnofacies in a fluvial basin can be useful for distinguishing paleoen-
vironmental changes and can also help in the recognition of larger-scale
stacking patterns in sequence-stratigraphic analysis.
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