Chronostratigraphy and geochronology: A proposed realignment

[摘要] We propose a realignment of the terms geochronology and chronostratigraphy that brings them broadly into line with current use, while simultaneouslyresolving the debate over whether the Geological Time Scale should have a“single” or “dual” hierarchy of units: Both parallel sets of units areretained, although there remains the option to adopt either a single (i.e.,geochronological) or a dual hierarchy in particular studies, as consideredappropri-ate. Thus, geochronology expresses the timing or age of events(depositional, diagenetic, biotic, climatic, tectonic, magmatic) in Earth’shistory (e.g., Hirnantian glaciation, Famennian-Frasnian mass extinction).Geochronology can also qualify rock bodies, stratified or unstratified, withrespect to the time interval(s) in which they formed (e.g., Early OrdovicianIbex Group). In addition, geochronology refers to all methods of numericaldating. Chronostratigraphy would include all methods (e.g., biostrati-graphy,magnetostratigraphy, chemostratigraphy, cyclostrati-graphy, sequencestratigraphy) for (1) establishing the relative time relationships ofstratigraphic successions regionally and worldwide; and (2) formally namingbodies of stratified rock that were deposited contemporaneously with unitsformally defined at their base, ideally by a GSSP (Global Boundary StratotypeSection and Point = “golden spike”) that represents a specific point in time.Geochronologic units may be defined and applied generally by either GSSPs or—ascurrently in most of the Precambrian—by Global Standard Stratigraphic Ages(GSSAs). Geochronologic units would continue as the time unitseons/eras/periods/epochs/ages, and chronostratigraphic units as the time-rock units eonothems/erathems/systems/series/stages. Both hierarchies would remainavailable for use, as recommended by a formal vote of the InternationalCommission on Stratigraphy in 2010. Geological context helps determine theappropriate usage of the component units.

[学科分类] 地质学

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