GSA Today: Putting Time In Its Place
In the March issue of GSA Today, seven scientists from six countries, led by Jan Zalasiewicz of the University of Leicester, propose a realignment of the terms “geochronology” and “chronostratigraphy” in an attempt to resolve the debate of whether units of the Geological Time Scale should have a single (time) or dual (time and time-rock) hierarchy.
In their system, which retains both parallel sets of units, with an option to adopt one or other when appropriate, geochronology refers to all methods of numerical dating and is used to express the timing or age of events in Earth’s history and to qualify rock bodies with respect to time intervals. Chronostratigraphy, on the other hand, includes all methods used to establish the relative time relationships of stratigraphic successions and to formally name stratified rock bodies.
In this way, both hierarchies would remain available for use – geochronologic units continuing as the time units (eons/eras/periods/epochs/ages), while chronostratigraphic units continue as the time-rock units (eonothems/erathems/systems/series/stages).
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