A Conceptual Framework for the Application of Trace Fossils

Trace fossils or ichnofossils are the fossilized tracks, excavations, and domiciles of animals. In general, these are taken to represent the vestiges of animal behavior. As such, trace fossils can be related to animal coping strategies in sedimentary environments. Those strategies can be associated with sedimentary / environmental conditions.

Burrows are classified according to their overall morphologies. The morphology of trace fossils is evaluated using the following nomenclature: shafts, tunnels, tubes, lining, infill, meniscae, spreite, and trample. The shape and form of trace fossils is also considered. Behavioral classifications are inferred, and provide a higher level of organization for ichnofossils. Behavioral inferences form the basis for the definition of ichnofacies.

Preservation of trace fossils depends on sedimentological and diagenetic factors. The fundamental physical parameters regarding ichnofossil preservation are the net sedimentation rate, the biogenic mixing rate, and the magnitude of physical reworking. Physical parameters relate to the presence or absence of textural contrast. Ichnofossil diagenesis comprises: (1) cementation of a finer-grained burrow wall [preferred tube cementation]; (2) cement precipitation or cement dissolution within a coarser-grained burrow fill [preferred burrow cementation]; (3) cement precipitation or dissolution adjacent to an ichnofossil [fabric-mimicking hypoburrow cementation]; and (4) concretion formation [nodular hypoburrow cementation].

This paper also documents the various animal responses to physical processes, referred to herein as “process ichnology”. Considered are ichnofossils associated with high or sporadically high sedimentation rates, the use of ichnofossils for their potential in revealing the cohesiveness of a substrate at the time of burrowing, trace fossils and burrow linings as sediment traps, and finally, trace fossils as penecontemporaneous strain indicators.

Other general applications of ichnology, including ichnofacies, stratigraphic utility, and reservoir analysis, are considered. These reside in a well-established framework and thus serve as a brief summary of previously conducted research.