An improved age framework for late Quaternary silicic eruptions in northern Central America |
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| Authors: | William I Rose F Michael Conway Carlos R Pullinger Alan Deino William C McIntosh |
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| Institution: | (1) Geological Engineering and Sciences, Michigan Technological University, Houghton, MI 49931 USA e-mail: raman@mtu.edu pulga@salnet.net, US;(2) Division of Science and Math, Arizona Western College, Box 929, Yuma, AZ 85366, USA, US;(3) Berkeley Geochronology Center, 2455 Ridge Rd., Berkeley, CA 94709, USA, US;(4) New Mexico Geochronology Research Laboratory, N.M. Bureau of Mines, New Mexico Tech, 801 Leroy Place, Socorro, New Mexico, 87801–4796, USA, MX |
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| Abstract: | Five new stepwise-heating 40Ar/39Ar ages and one new high-sensitivity 14C date of ash-fall and ash-flow deposits from late Quaternary silicic volcanoes in northern Central America document the eruption
rates and frequencies of five major rhyodacite and rhyolite calderas (Atitlán, Amatitlán, Ayarza, Coatepeque, and Ilopango)
located north of the basalt, andesite, and dacite stratovolcanoes of the Central American volcanic front. These deposits form
extensive time-stratigraphic horizons that intercalate regionally, and knowledge of dates and stratigraphy provides a valuable
framework for age determinations of more localized volcanic and nonvolcanic events. The new data, especially when integrated
with previous stratigraphic and dating work, show that all five calderas erupted several times in the past 200 ka and, despite
a lack of historic activity, should be considered as active centers that could produce highly explosive eruptions again. Because
of their locations near the highly vulnerable economic hearts of Guatemala and El Salvador, the risks of eruptions from these
calderas should be carefully considered along with risks of major earthquakes and volcanic front volcanoes, which are much
more frequent but inflict less severe and extensive damage. This investigation also includes some examples of dating efforts
that failed to produce reasonable results.
Received: 15 May 1998 / Accepted: 18 January 1999 |
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| Keywords: | Ages Calderas Late Quaternary Guatemala El Salvador |
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