Effectiveness of combined unspiked K–Ar and 40Ar/39Ar dating methods in the 14C age range

In this study, the effectiveness of combined unspiked K–Ar and 40Ar/39Ar dating methods as currently applied now at LSCE in the 14C age range was evaluated by studying two 30,000 years old phonolites from Tenerife (Canary Islands). New 40Ar/39Ar ages obtained in this work are comparable with the K–Ar ages, and of similar precision. This remarkable agreement obtained between the two dating methods in this young age range, validates the new LSCE 40Ar/39Ar facility and provides a very promising approach to calibrate the Quaternary timescale and to date key events such as geomagnetic field instabilities and climatic changes.The approach combining the 40Ar/39Ar and the unspiked K–Ar methods has the advantage that all the basic assumptions, which rule the K–Ar clock, are checked via the isochron approach. In the event of positive check, the 40Ar/39Ar and unspiked K–Ar ages can be pooled to produce very precise ages.

► Unspiked K–Ar and 40Ar/39Ar methods are applied on 30 ka old phonolites. ► Unspiked K–Ar and 40Ar/39Ar agree within errors and are of similar precision. ► Pooled ages are very precise. ► They can be used to discuss the accuracy of 14C ages in a volcanic environment.