Environmental Engineering Reference
In-Depth Information
4. SHALLOW-MARINE ENVIRONMENTS
The application of trace fossils to the dating of shallow-marine deposits has
focused mainly on Ediacaran and Paleozoic shallow-marine siliciclastic strata.
In such strata, ichnostratigraphy has been applied to three main problems: (1)
positioning of the Proterozoic/Cambrian boundary and dating of adjacent strata
based on the establishment of a number of trace-fossil zones (e.g.,
Buatois and
M´ngano, 2011; Jensen, 2003; MacNaughton and Narbonne, 1999
); (2) estab-
lishment of relative ages in Paleozoic siliciclastic successions based on ichno-
species of
Cruziana
and
Rusophycus
(e.g.,
Seilacher, 1970, 1992, 1994
); and
(3) establishment of relative ages in early Paleozoic siliciclastic units based
on ornamented burrows, such as
Arthrophycus
and related trace fossils (e.g.,
M
´
ngano et al., 2005; Seilacher, 2000
).
4.1 Proterozoic/Cambrian Boundary
The Proterozoic/Cambrian boundary Global Standard Stratotype-section and
Point (GSSP) is the only stratigraphic boundary established on ichnological
grounds. It was placed at the base of the
Treptichnus pedum
Zone at Fortune
Head, Newfoundland, Canada (
Fig. 3
;
Brasier et al., 1994; Landing, 1994;
Narbonne et al., 1987
), although more recent work has moved the base of
the zone slightly below the GSSP (
Gehling et al., 2001
).
FIGURE 3
The Proterozoic/Cambrian boundary Global Standard Stratotype-section and Point
(GSSP) at Fortune Head, Newfoundland, Canada. S¨ren Jensen's right hand is at the boundary. Sub-
sequent research demonstrated the presence of
Treptichnus pedum
some 4 m below the GSSP
(
Gehling et al., 2001
). Photograph courtesy of Jim Gehling.
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