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exceedingly rare in dune deposits as to be essentially non-existent. Thus without
trace fossils, the task of interpreting the paleoecology of eolian paleoenviron-
ments would be as hopeless as Odysseus' fleet being tossed about at the mercy
of the four winds.
The main take-home points of this chapter can be summarized briefly by the
following points:
1. Ancient dune deposits are generally devoid of body fossils, but trace
fossils—although sparse—do occur in sufficient quantity in some eolianites
to lend crucial help in interpreting the paleoecology of the paleoenviron-
ment. The Entradichnus Ichnofacies, including ichnogenera attributed to
both invertebrate and vertebrate animals, represents all the various recurrent
assemblages of trace fossils that characterize coastal and inland dune paleo-
environments.
2. Much of what is known about modern traces of dune dwellers comes from
observations made on the gently sloping, erosional, stoss side of the dune,
whereas the part of the dune that actually becomes preserved in the fossil
record is the steeply dipping, depositional, slip face of the dune. Thus, mis-
leading interpretations may result when seeking modern analogs for
ancient trace fossils. The stoss tends to exhibit more diverse, more delicate,
and less-deformed repichnial, pascichnial, and domichnial traces than does
the slip face, where most of the traces are repichnia that exhibit deformation
by sediment slippage and collapse.
3. There is trace-fossil evidence of occupation of the eolian environment by
some of the first land animals (arthropods) in the Early Paleozoic, perhaps
as early as the Late Cambrian. This suggests that at least some early life
forms on land were sufficiently hearty to withstand the harsh vicissitudes
of blowing winds and shifting sands.
4. Ichnological data in eolianites lend important information to paleoclimatic
studies because the trace-fossil occurrences provide evidence of the types of
organisms inhabiting the dunes and possibly also the seasonal nature of their
activity in monsoonal climates.
5. A unique ichnofabric in modern eolian deposits that has been unrecognized
in ancient eolianites heretofore is the distinctive pattern of disruption of
stratification resulting from sand-swimming behavior of infaunal verte-
brates moving around inside the dry sand of the dunes. Although a sand-
swimming ichnofabric has not been reported in the rock record, it must
be there, so ichnologists would be well advised to be on the lookout for such
an ichnofabric when examining ancient eolian sequences.
ACKNOWLEDGMENTS
This chapter benefited from constructive comments by Ken Glennie and Dirk Knaust.
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