Tidal Flats and Subtidal Sand Bodies - Trace Fossils as Indicators of Sedimentary Environments - page 514

2004b ). In the subtidal region, energy-related and other ecological parameters
can also vary across a single sand body, which leads to localized colonization
trends ( Desjardins et al., 2012a ).
The focus of this study is placed on macrotidal (tidal range

4m)
open-marine settings, in which tidal currents are the dominant sedimentary
processes. Excluded are the ichnofaunas of tidally influenced or tidally
dominated marginal-marine settings, such as estuaries, deltas, or interdistribu-
tary bays, which are typically of lower diversity in brackish-water environ-
ments (see Gingras et al., 2012 ), or contain freshwater trace fossils as in
the case of fluvio-estuarine transitions (see Buatois et al., 1997; M ´ ngano
and Buatois, 2004b ). In addition to the classic zonation for intertidal settings,
the environmental framework for tidal shelves adopted in this study is that of
Desjardins et al. (2010a) , where the position of the effective wave bases ( sensu
Flemming, 2005 ) serves to separate three main environmental zones: (1) the
outer shelf below the effective storm-wave base, (2) the inner shelf above the
effective storm-wave base and below the effective fair-weather wave base,
and (3) the shallow subtidal environment above the effective fair-weather
wave base and below the low-tide line, bathymetrically equivalent of the
shoreface as commonly defined for wave-dominated settings ( Plint, 2010 ).
The intertidal and supratidal environments lie landward of the shallow sub-
tidal environment ( Fig. 1 ).

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FIGURE 1 Sedimentary environments and sand-body distribution in tide-dominated shallow-
marine settings.