Concepts and Methods of High-Resolution Event Stratigraphy

Modern geological analyses involving sedimentary rocks require a high­ resolution system of dating, integrating, and correlating diverse strati­ graphic, geochemical, and paleontological data that also takes into account the possibility that short-term phenomena (100 kyr or less) exercise a strong control on sedimentation. Such phenomena may be extraterrestrial, tectonic, volcanic, oceanographic, climatic, sedimentologic, and/or bio­ logic in origin. Some reflect unpredictable perturbations of local to global scale. But most short-term phenomena are predictable and may be either autocyclic (locally regulated, with limited stratigraphic continuity) or allo­ cyclic in nature (regionally to globally regulated, with extensive strati­ graphic continuity) (Beerbower 1964). A stratigraphic system based on short-term phenomena would ideally be chronostratigraphic, involving the identification and regional tracing of time lines (isochronous surfaces or very thin event deposits), and easily integrated with refined, independently derived biostratigraphic and geochronologic systems. An intensive search for such a new and revolutionary system of stratig­ raphy has been prompted in many parts of the Phanerozoic by attain­ ment of plateaus in stratigraphic resolution utilizing the more standard tools of magnetostratigraphy, biostratigraphy, and geochronology: Most magnetic reversals have been identified; biostratigraphic systems can be no more refined than the maximum evolutionary rates of component taxa and their major structures (known for many favored groups); and geo­ chronology is regulated by the analytical confidence limits of radiometric