The stratigraphy, age and correlation of post-18 cal. ka eruptive products from Chaitén Volcano within the super-humid (western) to semi-arid (eastern) Andean environments straddling southern Chile & Argentina

BRENT ALLOWAY; GUSTAVO VILLAROSA; PATRICIO I. MORENO; DE POL-HOLZ; NICK PIERCE; VALERIA OUTES

Congreso; CITIES ON VOLCANOES 9; 2016

The2008 eruption of Chaitén Volcano in southern Chile was the first explosiverhyolitic eruption to have occurred in the last century and provided anunprecedented scientific opportunity to examine all facets of the eruptionranging from magma rheology/ascendency rates to ash-fall effects on biota andinfrastructure. Despite the flurry of research activity in the aftermath of the2008 eruption very little was then known about its eruptive history. Up to veryrecently it was thought that the last eruption prior to the 2008 event occurredc. 9600 14C years ago. Since that initial survey, a number of subsequentresearchers have recognised additional eruptive products but theirstratigraphy, age, correlation and geochemical attributes have not beensystematically described and/or recorded. In this study, we provide a very detailed examination of the andiccover-beds adjacent to Chaitén Volcano, record a series of hitherto unknown rhyoliticeruptive products and place all previous observations firmly within a coherentstratigraphic framework and eruptive inventory that will ultimately be usefulfor accurately determining long-term eruptive tempo as well as correspondingtemporal changes in magmatic evolution. Through major and trace element glassshard geochemistry we are able to confidently verify eruptive source andindicate that Chaitén Volcano has been continuously but intermittently activeas far back as c. 18 cal. ka BP.