BIOSTRATIGRAPHY: AN ART THAT NATURE MAKES

A deep understanding of how fossils are used to tell time is essential for editors, reviewers and researchers dealing with Phanerozoic strata. On the face of it, biostratigraphy seems simple, but a real feel for its strengths and limitations comes with the experience of developing a biozonation oneself. Relatively few paleontologists seem to have this practical background, but it is still important to teach the concepts within the framework of sampling, taxonomy, biogeography, paleoecology and taphonomy. Unfortunately, like other fundamental components of a classical geological education, the specifics of biostratigraphy have been diluted and deëmphasized. Textbooks commonly oversimplify the subject by giving examples no more advanced that William Smith's principle of faunal succesion. Biostratigraphy may be explained in association with evolutionary principles even though these are essentially unrelated. The biostratigraphy chapter may be orphaned without its tenets being shown in action in correlation, basin analysis and sequence stratigraphy. Paleontologists can shoulder some blame too, for having allowed a proliferation of terminology and tangential biozonal categories that have limited application or are even notionally flawed. These derivatives are portrayed in textbooks, guides and codes in place of realistic examples. Consequently, graphical illustrations may contain errors if the validity of every line that may have a temporal connotation is not policed. Submitted manuscripts may betray a misunderstanding of the temporal precision of an existing biozonal scheme and what can or cannot be safely interpreted. Correlations based on biostratigraphy may take on a certainty that is unfounded; or they may be considered flimsy and trumped by other methods, like isotope excursions or magnetic reversals. Practitioners may misunderstand the meaning of biozones as the primary rock observations get massaged first into grids and thence into chronostratigraphic subdivisions. These pitfalls are serious because almost any scientific activity on Phanerozoic strata or sediments relies on relative time as told by fossils.