TWO REFERENCE MATERIALS, TRACHYTES MDO-G AND ISH-G, FOR ARGON DATING (K-AR AND 40AR/39AR) OF PLEISTOCENE AND HOLOCENE ROCKS

With the recent extension of K‐Ar dating methods within the Upper Pleistocene time, the use of new standards is recommended to allow calibration and inter‐laboratory comparisons. For this purpose, two pure microlitic groundmass reference materials were prepared from trachy‐basaltic lavas: Trachyte (MDO‐G) from Mont Dore, Puy de Sancy, Massif Central is around 250 000 years old; the second Trachyte (ISH‐G) from the Isle of Ischia, Gulf of Naples (Italy), is historical: Arso flow erupted on Christmas 1301 ‐ January 1302 AD.