Jan Zalasiewicz, Maria Bianca Cita, Frits Hilgen, Brian R.
Pratt, André Strasser, Jacques Thierry, Helmut Weissert
Abstract
We propose a realignment of the terms geochronology
and chronostratigraphy that brings them broadly into line with current
use, while simultaneously resolving the debate over whether the Geological Time
Scale should have a “single” or “dual” hierarchy of units: Both parallel sets
of units are retained, although there remains the option to adopt either a
single (i.e., geochronological) or a dual hierarchy in particular studies, as
considered appropri-ate.
Thus, geochronology expresses the timing or age of
events (depositional, diagenetic, biotic, climatic, tectonic, magmatic) in
Earth’s history (e.g., Hirnantian glaciation, Famennian-Frasnian mass
extinction). Geochronology can also qualify rock bodies, stratified or
unstratified, with respect to the time interval(s) in which they formed (e.g.,
Early Ordovician Ibex Group). In addition, geochronology refers to all methods
of numerical dating. Chronostratigraphy would include all methods (e.g.,
biostrati-graphy, magnetostratigraphy, chemostratigraphy, cyclostrati-graphy,
sequence stratigraphy) for (1) establishing the relative time relationships of
stratigraphic successions regionally and worldwide; and (2) formally naming
bodies of stratified rock that were deposited contemporaneously with units
formally defined at their base, ideally by a GSSP (Global Boundary Stratotype
Section and Point = “golden spike”) that represents a specific point in time.
Geochronologic units may be defined and applied generally by either GSSPs or—as
currently in most of the
