The glaciovolcanic evolution of the Copahue volcano, Andean Southern Volcanic Zone, Argentina-Chile

BÁEZ, ALEJANDRO D.; BÁEZ, WALTER; CASELLI, ALBERTO T.; MARTINI, MATEO A.; SOMMER, CARLOS A.

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

ELSEVIER SCIENCE BV

Año: 2020 vol. 396

0377-0273

Glaciovolcanismproduces distinctive features that are useful paleoclimate proxies for the distribution of past icesheets and glacier extent. The Copahue volcano located in the Andean Southern Volcanic Zone, Argentina-Chile, isan active composite volcano known to have glaciovolcanic features such as lava bodies with glassy margins andanomalous cooling fractures. However, the emplacement conditions of these products and the influence of Pleistoceneglaciations on the evolution of the Copahue volcano remains poorly understood. In this contribution, wepropose a model for glaciovolcanic evolution of the Copahue volcano based on the analysis, interpretation, andmapping of its products. Ten lithofacies are described on the eastern flank of Copahue volcano exhibiting severalexamples of glaciovolcanism. The evolution of the Copahue volcano can be divided into two main sequences: theAncient Sequence (S1) and the Young Sequence (S2), separated by a major erosive phase. The S1 (early-middlePleistocene-late Pleistocene) consists of an initial subaerial effusive stage followed by a major glaciovolcanicstage, during which a thick ice cap existed and the edifice grew beneath an englacial lake with the eventual formationof a lava-fed delta. The S2 (late Pleistocene-Present) is defined by mainly effusive activity during periodsof glacial advance and retreat recorded by an alternation of unconfined subaerial lavas and ice-confined lavas. Theevolution of the Copahue volcano therefore indicates two glaciations in the Copahue-Caviahue area during thelate Pleistocene, in contrast to a single glaciation. Based on the glacial history in the areawe associate the first glaciationwith the end of Marine Isotope Stage 3 (57?29 ka) and/or the Last Glacial Maximum period(26.5?19.0 ka), and the second less-extensive glacial period with the Antarctic Cold Reversal (14.5?12.9 ka).