Revised astronomically calibrated 40Ar/39Ar ages for the Fish Canyon Tuff sanidine - Closing the interlaboratory gap

Abstract

The 40Ar/39Ar geochronology method is capable of high precision (<0.05%), but remains limited by relatively large uncertainties in 40K decay constants and the ages of natural reference mineral standards. The most widely used 40Ar/39Ar reference mineral is the well-known ca. 28 Ma Fish Canyon Tuff sanidine (FCTs). Several studies have attempted to calibrate FCTs against astronomically tuned tephra in Crete (Faneromeni A1 tephra) and Morocco (Messâdit Mes4 tuff) as well as deep-sea sedimentary sequences. Previously reported astronomically tuned ages range from 28.126 ± 0.019 to 28.21 ± 0.18 Ma (2σ), a range of ~0.3%, compared to precision levels of <0.05% achievable by new generation, multi-co..