Classification of Trace Fossils
Published:January 01, 1984
Classification is simply the orderly arrangement of voluminous amounts of information to aid in interpreting various kinds of relationships between items and also in communicating ideas about these items with other workers. Five different aspects of trace fossils have provided a basis for their classification, i.e., based on preservation (toponomy), taxononomy (systematics of presumed trace-makers), ichnotaxonomy (systematics of trace fossils), ethology (behavior) and paleoenvironment (bathymetry, etc.). The preservational and taxonomie classification schemes are primarily descriptive (i.e., objective); the behavioral and paleoenvironmental approaches to classification, on the other hand, are largely interpretive (i.e., subjective).
Ichnology, sometimes divided into neoichnology and paleoichnology (palichnology), depending on whether you are dealing with modern or ancient settings, is centered on the study of biogenic (i.e., biologically produced) structures. These are categorized as follows (Table II-1).
A number of specialized terms, most of which are listed in the Glossary at the end of this book, apply to various kinds of biogenic structures. For example, a “shaft” is a dominantly vertical burrow; a “tunnel” is a dominantly horizontal burrow (Fig. 2-l); a “U-shaped burrow” or “U-tube” is one comprising two shafts that join at depth in the sediment. If shafts and/or tunnels form a complex unit of highly branched burrows, the entire structure is a “burrow system”. A system of interconnected burrows is a “maze” or “gallery”, if dominantly horizontal, or “boxwork”, if both horizontal and vertical components are included (Fig. 2-2).
Some burrows possess a “lining”, which is a distinct, thickened, burrow wall reinforced by mucus-like
Figures & Tables
Ichnology: The Use of Trace Fossils in Sedimentology and Stratigraphy
Ichnology is a fascinating field of endeavor. As with science in general, it is a process of solving mysteries–in this case, mysteries of fossil behavior. In a very real sense the ichnologist is Sam Spade or Sherlock Holmes–following footprints, searching for traces of dastardly deeds, studying artifacts, attempting to reconstruct a sequence of events from subtle clues, pursuing the identity of someone (or something) long dead. Who was the culprit? What was he/she doing? Where was he/she living, working or going? Not only intellectually intriguing, ichnology also has practical application and economic importance. In today’s frenzied quest for energy and mineral resources, exploration geologists value every tool that aids their search. Ichnologic observations and analyses can help the sedimentologist reconstruct ancient depositional environments, help the stratigrapher correlate sedimentary strata, help the paleontologist determine the nature of fossil communities, and help the geochemist determine the effect of organisms on sediment composition. This publication was written to serve as a comprehensive and intelligible introduction to ichnology for anyone with even rudimentary geologic training, whether or not that person enrolls in a formal course on the subject. The book emphasizes sedimentologic, stratigraphic and paleoecologic al aspects of ichnology.