40Ar/39Ar ages of the older eruptive units of Somma-Vesuvius volcano, Italy
Abstract
40Ar/ 39Ar ages have been measured on the older major explosive eruptions of Somma-Vesuvius volcano in Italy. These eruptions all have pumice fall, and pyroclastic surge and flow deposits. The eruptive history of Somma-Vesuvius volcano has previously been based on uncalibrated 14C ages, mostly on carbon from paleosols, reported by Delibrias and others (1979) and Sigurdsson and others (1985). These assigned ages, plus measured 14C ages, calibrated 14C ages (denoted as 14C*) and 40Ar/ 39Ar ages (all in years) are:
Mercato Tuff ~8500 years 14C=8263±29, 14C*=9250±49, 40Ar/ 39Ar=9155±461, 9541±460 Verde Tuff ~15000 years 14C=14420±130, 14C*=17200±380, 40Ar/ 39Ar=18456±302 Pomici di Base ~17000 years 14C=17229±398, 14C*=20360±139, 40Ar/ 39Ar=21759±306, 21568±328 The assigned ages are from Delibrias (1979). The 14C ages (Aleisso and others, 1971, 1973, 1974, 1978) use 1σ counting errors reported by laboratories. The uncertainty in calibrated 14C ages (above) are these reported uncertainties plus 1σ uncertainties of the calibration curves in IntCal04 (Reimer and others, 2004). The uncertainties in 40Ar/ 39Ar ages are 1σ errors. Pomici di Base and Mercato samples were analyzed twice. The weighted mean of plateau ages for Pomici di Base fall unit is 21,670 ± 224 years, and the weighted mean of isochron ages is 21,313 ± 408 years. The weighted mean of plateau ages for Mercato Tuff is 9348 ± 326 years, and the weighted mean of isochron ages is 9577 ± 332 years. The period of time from 0-12.4 ka used in calibrating 14C ages is based on dendrochronologically-dated tree ring samples. The calibration older than 12.4 ka is based on marine samples, primarily corals, and the marine calibrations are in dispute. The calibrated 14C ages above are based on IntCal04. Chui and others (2007) have presented another calibration based on fossil corals. In the younger part of their record, less than 30,000 years, the age difference averages less than 100 years. Aleisso and others, 1971, 1973, 1974, and 1978, University of Rome Carbon-14 Dates IX: Radiocarbon, v. 13, 15, 16, and 20. Chiu, T.C., Fairbanks, R.G., Cal, L., and Mortlock, R.A., 2007, Analysis of the atmospheric 14C record spanning the past 50,000 years derived from high-precision 230Th/234U/238U, 231Pa/235U, and 14C dates on corals: Quaternary Science Reviews, 26:18-36. Delibrias, G., DiPaola, G.M., Rosi, M., and Santacroce, R., 1979, La Storia Eruttiva Del Complesso Volcanico Somma Vesuvio Ricostruita Dalle Successioni Piroclastiche Del Monte Somma; Rendiconti Societa Italiana di Mineralogia e Petrologia, 35:411-438. Reimer, P.J.and others, 2004, IntCal04 Terrestrial Radiocarbon Age Calibration, 0-26 Kyr BP: Radiocarbon, 46:1029-1058. Sigurdsson, H., Carey, S., Cornell, W., and Pesdatore, T., 1985, The Eruption of Vesuvius in A.D. 79, 1985: National Geographic Research, 1:332-387.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.V11B2026L
- Keywords:
-
- 8428 Explosive volcanism;
- 8455 Tephrochronology (1145);
- 8486 Field relationships (1090;
- 3690);
- 8488 Volcanic hazards and risks;
- 8494 Instruments and techniques