Attempting discussion of the International Chronostratigraphic Chart after the Global Standard Boundary Stratotype Section and Point

Abstract

<p indent=0mm>To date, approximately two-thirds of the Phanerozoic chronostratigraphic boundaries have been defined in terms of the Global Standard Boundary Stratotype Section and Point (GSSP) concept in the International Chronostratigraphic Chart. However, in practice, almost all definitions and correlations of these boundaries are controversial, and some of the definitions are indeed questionable. Consequently, the definitions of some boundaries for the standard of correlation become almost meaningless, and it is therefore necessary to reexamine the guiding ideology and research methods for determining stratigraphic boundaries. In addition, the current International Chronostratigraphic Chart is no longer able to meet the need for accuracy of the temporal and spatial framework for Earth system science. Therefore, it is necessary to establish a new generation of the International Chronostratigraphic Chart after the GSSP. Given the problems encountered in the establishment and practice of the International Chronostratigraphic Chart, this paper proposes that the International Chronostratigraphic Chart after the GSSP should be developed to solve the following issues: (1) Improving the time resolution; (2) improving the identifiability of stratigraphic boundaries; (3) improving the isochronism of stratigraphic boundaries; (4) establishing a standard for chronostratigraphic boundaries that is suitable for accurate correlation of different sedimentary facies in different regions; (5) establishing objective, repeatable, and verifiable criteria for the definition and selection of GSSPs; and (6) ensuring that the chronostratigraphic boundaries reflect the historical stages of the evolution of Earth. The present paper attempts to combine biostratigraphy and event stratigraphy to define chronostratigraphic boundaries, and takes the geological event surface as an important criterion for defining, selecting, and identifying GSSPs. In the specific approach, the speciation event of the first widely distributed species above the top surface of the event stratigraphic unit, that is, the base of the first widely distributed biozone above the top surface of the event stratigraphical unit, should be selected as the biostratigraphic definition of a chronostratigraphic boundary (the first criterion). The section with the shortest distance between the first appearance datum (FAD) of the index fossil selected to define a chronostratigraphic boundary and the top surface of the event stratum should be chosen as the boundary stratotype section (the second criterion), and the FAD of the index fossil in the section is the GSSP. The top surface of the event stratum below the index fossil, as the biostratigraphic definition of a chronostratigraphic boundary, is an important reference criterion for identification and correlation of chronostratigraphic boundaries. Within the framework of biostratigraphy, the records of all types of geologic events and other strictly isochronous natural boundaries are used for further division and more accurate correlation of deposits in detail, which may improve the resolution of the stratigraphic division and the identifiability of stratigraphic boundaries. This would allow a new generation of the International Chronostratigraphic Chart to reach the same time scale as the Quaternary (tens to hundreds of thousands of years) and improve the identifiability of chronostratigraphic boundaries in the field to benefit geological mapping.