Two examples are described here to illustrate its potential. Etna, the good correlation observed between (Ra-226)(0) activities at the time of eruption and Th contents in lava flows from the last two millennia [M. 132 (1995) 25-41] is used to infer the ages of several newly analysed lava flows. We also present a whole set of new U-series data on historical, recent, and older samples from Merapi (Indonesia), and show that the (Ra-226)/Ba ratio has probably maintained a quasisteady state value during at least the past four millennia, and can be used to infer the (Ra-226)(0)/Ba ratio of old volcanics at the time of eruption, and thus their ages. The promising results obtained in this work should encourage new systematic U-series studies to test the applicability of such methods to other permanently active volcanoes showing Ra-226 excesses.
Th disequilibria can be used to date Holocene volcanic rocks from some well selected volcanoes. 132 (1995) 25–41] is used to infer the ages of several newly analysed lava flows. Two examples are described here to illustrate its potential. Etna, the good correlation observed between ( activities at the time of eruption and Th contents in lava flows from the last two millennia [M. Etna: constraints from U–Th–Ra–Pb radioactive disequilibria and Sr isotopes in historical lavas, Earth Planet. The calculated ages are in good agreement with those deduced from the archaeomagnetic curve describing the variation of the geomagnetic field direction in southern Italy [J.
Patane, Archaeomagnetic dating of Mediterranean volcanics of the last 2 100 years: validity and limits. Comparison with C-14 ages available on three samples [R. Keller, Temporal variations in magma composition at Merapi volcano (Central Java, Indonesia): magmatic cycles during the past 2000 years of explosive activity, J.