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Trace fossils represent both sedimentological and palaeontological entities, providing a unique blending of potential environmental indicators in the rock record. Trace fossils and trace fossil suites can be employed effectively to aid in the recognition of various discontinuity types and to assist in their genetic interpretation. Ichnology may be employed to resolve surfaces of stratigraphic significance in two main ways: (1) through the identification of discontinuities using substrate-controlled ichnofacies (the firmground Glossifungites ichnofacies, the hardground Trypanites ichnofacies and the woodground Teredolites ichnofacies); and (2) through careful analysis of trace fossils in vertical (soft-ground) successions (analogous to facies successions). Integrating the data derived from substrate-controlled ichnofacies (so-called omission suites) with palaeoecological data from vertically and laterally juxtaposed softground ichnological successions greatly enhances the recognition and interpretation of a wide variety of stratigraphically significant surfaces. When this is coupled with conventional sedimentary facies analysis and sequence stratigraphy, a powerful approach to the interpretation of the rock record is generated.

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Magnetic resonance images are paired with petrographic data to evaluate the textural characteristics of rocks dominated by Macaronichnus segregatis, a trace fossil that is commonly associated with rocks deposited in shallow, marginal marine sedimentary environments. MRI techniques used revealed the three-dimensional geometry of the trace fossil. Burrows are typically horizontal and in plan view range between straight, sinuous, meandering, and spiral geometries. Changes in burrow morphology may be related to population density and patchy resource distribution. The pairing of MRI and petrographic data helped map the distribution of porosity in the burrowed rock. Because MRI images represent complex composites of nuclear spin density and MR relaxation times, each of which is related to pore size, stronger MR signals must be calibrated to known porous zones by integrating petrographic data with MR data. The complex distribution of porosity and its relationship to the matrix show that this fabric represents a dual porosity-permeability system and may affect the resource (reservoir or aquifer) quality of similarly burrowed sedimentary rocks. Future research should elaborate upon the porosity-permeability model for this and similar fabrics.

Indentation tests are used to detail firmness profiles from intertidal creek deposits and wave-exhumed substrates at Willapa Bay. Both of these sedimentological settings are characterized by occurrences of modern Glossifungites assemblages. Firm substrates associated with the intertidal-creek deposits are derived from dewatered modern sediments, whereas firmgrounds associated with wave erosion consist of dewatered and compacted Pleistocene strata. The Pleistocene firmgrounds are notably firmer than those derived from modern deposits. A strong correlation between sediment firmness and burrowing behavior is evident in these deposits.In tidal-creek systems, the comparatively firm cutbank is characterized by unlined, large-diameter, open burrows that form a Glossifungites assemblage. Intertidal point-bar deposits contain a softground suite consisting of mucous-lined, small-diameter, dominantly vertical traces. Finally, a softground suite of robust, mucous-or mud-lined, vertical and horizontal traces are observed in intertidal-flat deposits. In contrast, Pleistocene firmgrounds generally contain large-and small-diameter traces, with dominantly vertical architectures (Thalassinoides-, Gastrochaenolites-, Diplocraterion-, or Arenicolites-like burrows), depending upon the firmness of the substrate.Glossifungites occurrences on modern firmgrounds are temporally insignificant, whereas similar occurrences in Pleistocene substrates are temporally significant. Contrasting these two databases suggests that the stratigraphic significance of a Glossifungites-demarcated discontinuity can be assessed in the rock record. Several criteria that are useful for identifying temporally significant surfaces are suggested, including: absence of compaction of the Glossifungites assemblage; presence of well-preserved burrow sculptings; and planar to gently undulatory erosional surfaces as opposed to surfaces with notable topographic relief. Conceptual models demonstrate that muddy substrates potentially require several millennia to compact and dewater. Sandy deposits, on the other hand, have indeterminate significance.