HR: 1340h
AN: V13D-0576    [Abstracts]
TI: Volcanic Evolution and Geochronology of Nevados de Chillan Volcano, Chile.
AU: * Mee, K
EM: katymee@hotmail.co.uk
AF: Department of Environmental Science, Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: Gilbert, J S
EM: j.s.gilbert@lancaster.ac.uk
AF: Department of Environmental Science, Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: Pringle, M
EM: mpringle@mit.edu
AF: 54-1122, Department of Earth, Atmospheric and Planetary Sciences, 77 Massachusetts Avenue, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 United States
AB: Studies of volcanoes with variable snow and ice cover and a long history of volcanic activity enable reconstructions of past climates and eruptive environments. Nevados de Chillán volcano has been active since at least 640 ka BP through a number of glacial and interglacial periods and has produced a wide range of textures thought to be the result of lava-snow/ice interactions. Six new ⁴⁰Ar/³⁹Ar ages, along with eight existing ⁴⁰Ar/³⁹Ar ages have allowed more thorough analysis of the geochronology of Nevados de Chillán. These have been combined with paleoenvironment reconstructions and the marine oxygen isotope record to interpret the volcanic evolution of Nevados de Chillán volcano. With the exception of the 640 ka Los Pincheira lavas, the newly mapped volcanic facies have been erupted since 100 ka BP, although some undated facies may be older than this. From 100 ka BP, volcanism appears to have been concentrated along caldera wall sections before shifting towards the central regions of the volcano from 52 ka BP. This has resulted in the evolution of the two modern day volcanic centres, Cerro Blanco and Las Termas. In terms of the volcanic evolution of Cerro Blanco, three periods can be identified: (1) a constructive period, pre-caldera-collapse, whereby several, large volume lava flows were erupted (these units are assigned to an older volcanic complex); (2) a destructive period of syn-caldera-collapse activity, which produced several lava flows erupted along a section of caldera wall; and, (3) a constructive period of lava flow effusion and dome growth associated with the modern day volcanic complex. The volcanic evolution of Nevados de Chillán is similar to many Andean volcanoes where large-scale caldera-collapse is followed by stratocone growth.
DE: 8408 Volcano/climate interactions (1605, 3309)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005