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Uchman (2004)
noted that a few graphoglyptid ichnotaxa have rather narrow
stratigraphic ranges. Examples include
Glockerichnus alata
(
Fig. 6
C) (only
known from the Eocene) and
Rotundusichnium zumayense
(Maastrichtian-
Eocene). Nevertheless, most graphoglyptid ichnotaxa have longer stratigraphic
ranges, spanning the Cretaceous to the Neogene (
Uchman, 2003, 2004
).
6. CONCLUSIONS
The applications of trace fossils in biostratigraphy are more limited than in
fields such as facies analysis and sequence stratigraphy. However, in the right
circumstances, trace fossils can provide crucial biostratigraphic data. It is
worthwhile to consider that the most important boundary in the stratigraphic
record, the Proterozoic/Cambrian boundary, is recognized based on the first
appearance of
Treptichnus pedum
. Although ichnostratigraphy seldom can
compete with high-resolution biostratigraphy based on other fossil groups,
many complex trace fossils still do present a remarkable macroevolutionary
pattern in the stratigraphic record. Also, where body fossils are absent, scarce,
or unevenly distributed (e.g., Early Paleozoic shallow-marine sandstones,
Cambrian deep-marine deposits, continental red beds), ichnological data may
provide a crucial age constraint.
In short, the application of ichnology in biostratigraphy, the so-called ichno-
stratigraphy, remains a poorly explored field that deserves further analysis. At
the very least, documentation and discussion of stratigraphic ranges should be a
standard part of trace-fossil studies. Given the biostratigraphic insights that
have arisen from databases compiled for the Proterozoic/Cambrian boundary
(
Crimes, 1987, 1992; Jensen, 2003
) or for deep-marine ichnotaxa through time
(
Uchman, 2003, 2004
), there probably is much scope for compilations focused
on other aspects of the trace-fossil record. Such studies may provide a refresh-
ing, new understanding of the ichnological record.
ACKNOWLEDGMENTS
Jim Gehling provided the Fortune Head photograph and Ver´nica Krapovickas provided
some of the vertebrate footprint photographs. We thank S¨ren Jensen for his valuable review
and Dirk Knaust and Richard Bromley for inviting us to write this chapter and for editing the
chapter. Funding was provided by Natural Sciences and Engineering Research Council of
Canada (NSERC) grants to M. G. M. (Discovery Grant 311727-05 and -08) and L. A. B.
(Discovery Grant # 311726-05 and -08). Geological Survey of Canada internal review of
the chapter was provided by JamesWhite. This is Earth Sciences Sector contribution 20110303.
REFERENCES
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