Shallow-Marine Carbonates - Trace Fossils as Indicators of Sedimentary Environments - page 687

et al., 1977; Lukasik and James, 2003; Wilson and Palmer, 1994 ). The tapho-
nomy of trace fossils is controlled by the chemical microenvironment around the
burrows and borings, which act as open conduits to the sediment/water interface
and facilitate diagenetic processes such as the precipitation of calcite, dolomite,
celestite, or pyrite ( Bertling, 1999; Gingras et al., 2004 ).
Furthermore, diagenesis is capable of total alteration of the deposits as well
as the development of secondary porosity. Because of common early-diagenetic
consolidation of carbonate sediment, burrow-related porosity is an even more
important aspect for the quality of hydrocarbon reservoirs and aquifers
than in siliciclastic deposits ( Cunningham et al., 2009, 2012; Knaust, 2009;
Pemberton and Gingras, 2005 ).
3. ICHNOFACIES
Following the gradient on a carbonate platform (or ramp) from a relative proxi-
mal (landward) to distal (seaward) position, there are three ichnofacies of
importance for the reconstruction of paleoenvironments ( Fig. 1 ): (1) Psilon-
ichnus Ichnofacies, (2) Skolithos Ichnofacies, and (3) Cruziana Ichnofacies.
During periods with strongly reduced or no deposition (condensation, omission)
and progressing lithification, each of the before-mentioned ichnofacies can
be overprinted by the substrate-controlled (4) Glossifungites Ichnofacies, or
the (5) Trypanites Ichnofacies.
FIGURE 1 Conceptual model of a carbonate ramp with characteristical depositional environments
and related ichnofacies (see text for explanations). Note the complexity and resulting variation in
ichnofacies occurrence.