The Cretaio Tephra of Ischia (Italy)
Journal of Volcanology and Geothermal Research, 53 (1992) 329-354 329 Elsevier Science Publishers B.V., Amsterdam A comprehensive study of pumice formation and dispersal: the Cretaio Tephra of Ischia (Italy) G. Orsi a, G. Galloa, G. Heikenb, K. Wohletzb, E. Yub and G. Bonani¢ aDipartimento di Geofisica e Vulcanologia, University of Naples, Naples, Italy bLos Alamos National Laboratory, Los Alamos, NM, USA ¢Institut fur Mittelenergiephysik, ETH, Zurich, Switzerland (Received August 14, 1991; revised and accepted March 4, 1992 ) ABSTRACT Orsi, G., Gallo, G., Heiken, G., Wohletz, K., Yu, E. and Bonani, G., 1992. A comprehensive study of pumice formation and dispersal: the Cretaio Tephra of Ischia (Italy). J. Volcanol. Geotherm. Res., 53: 329-354. The Cretaio Tephra is a small-volume ( <0.02 km 3 ) pumice deposit on the island of Ischia in Italy. It was erupted during historical time and is associated with a tuff ring-dome complex extruded along a N-S-trending normal fault system bordering the east side of the Mt. Epomeo resurgent block. ~4C ages of the deposit average 1860 a B.P., which is in agree- ment with the potsherds found in paleosols underlying and overlying the deposit. The eruption sequence consists of 7 members; most of these members are pumice fall deposits, one is an ash and pumice fallout and another is a surge bed. The tephra have a trachytic-phonolitic composition. All chemical characteristics, includingmajor and trace elements, and Sr-isotope composition are homogeneous throughout the sequence. The vesicularity of pumice clasts does not show any systematic change; the erupted magma had the same amount of volatiles, the same flux and vesicle growth behavior throughout the eruption sequence.
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