Incremental heating of Bishop Tuff sanidine reveals preeruptive radiogenic Ar and rapid remobilization from cold storage

Recent improvements in analytical and microsampling techniques for multiple geochronometers have resulted in datasets with unprecedented temporal and spatial resolution. These advances are accompanied by the discovery of crystal- and outcrop-scale complexities previously obscured by low analytical precision. Single-crystal incremental heating resolves subtle, intracrystal isotopic heterogeneity, allowing for more-accurate ⁴⁰Ar/³⁹Ar eruption ages. The eruption ages of widespread volcanic ash deposits are critical for calibrating the geologic timescale, and thus their accuracy has substantial implications for the geologic, biologic, and global climate records. Complex distribution of ⁴⁰Ar/³⁹Ar dates in the deposits of supervolcanic eruptions requires rethinking the magmatic processes and their effect on the ⁴⁰Ar/³⁹Ar system, specifically the extent of cooling and remobilization during the decades to centuries preceding these events.