Modern Paleontology: Using Biostratigraphy to the utmost

Abstract

Emphasized here is the presence of two "types" of biostratigraphy. The first, associated with Alcide d'Orbigny who was its discoverer, consists of the relatively small number of marked changes in the overall marine, benthic, chiefly level-bottom biota. These are the boundaries between d'Orbigny's étages and sous-étages, which I have recently termed Ecologic-Evolutionary Units and Subunits. The second, associated with Albert Oppel who was their discoverer, are the within étage or Ecologic-Evolutionary Unit changes of a more gradual type. The gradual changes consist of the within community, species-to-species, changes shown by each genus belonging to each community. By paying more attention to the character of the changes occurring within each community, genus-by-genus, and then overlapping the subsequent Oppelian zonation possible with that taken from adjacent, interfingering communities, we may achieve a higher level of reliable, more precise biostratigraphy than by merely using miscellaneous taxa from varied communities. This approach requires that an ecostratigraphic sampling program be employed, i.e., tracking specific communities, through evolutionary time (within each ecologic-evolutionary unit), from section to section (because few sections represent the same community, i.e., environment, for a geologically lengthy time interval). This approach maximizes the phyletic evolutionary content of the fossil record, the Oppelian, while also taking advantage of extinction, adaptive radiation and dispersal, the d'Orbignyan.