Trace fossils represent both sedimentologic and paleontologic entities and, as such, represent 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 types of discontinuities and to assist in their genetic interpretation. Ichnology may be employed to resolve surfaces of sequence stratigraphic significance in two main ways: (1) through the recognition of substrate-controlled ichnofacies, which mark time gaps between the original deposition of a unit (with or without softground burrowing) and later superimposition of a postdepositional trace-fossil assemblage, and (2) through careful analysis of vertical ichnological successions (analogous to facies successions). Integrating the data derived from substrate-controlled ichnofacies with data from vertical ichnological successions provides a powerful tool for the recognition and interpretation of important sequence stratigraphic surfaces.