The Ichnofacies Paradigm: A Fifty-Year Retrospective

The ichnofacies paradigm endures as the elegant, unifying framework within which accurate ichnological observations and reliable environmental interpretations can be derived from the rock record. These temporally and geographically recurring, strongly facies-controlled groupings of trace fossils reflect specific combinations of organism behavior (ethology), and constitute the benchmark animal-sediment responses to optimum environmental conditions. Seilacherian ichnofacies are distinctive, archetypal associations of traces. Ichnofacies are part of the total aspect of the rock, and consist of primary biogenic structures imparted by organisms responding in predictable ways to variations in energy conditions, deposition rates, food resource types, substrate consistency, water salinity, oxygenation, subaerial exposure, substrate moisture, and temperature, among others. Like lithofacies, ichnofacies are subject to Walther's Law, have lateral continuity, display predictable vertical successions, and lead to mappable constructs. Like all facies analyses, interpretations of ichnofaunas are improved substantially when evaluated in the context of the host rocks and their sedimentologic and stratigraphic implications.