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 distinctivefeatures that are useful paleoclimate proxies for the distribution of past ice sheetsand glacier extent. The Copahue volcano located in the Andean Southern VolcanicZone, Argentina-Chile, is an active composite volcano known to haveglaciovolcanic features such as lava bodies with glassy margins and anomalouscooling fractures. However, the emplacement conditions of these products andthe influence of Pleistocene glaciations on theevolution of the Copahue volcano remains poorly understood. In thiscontribution, we propose a model for glaciovolcanic evolution of the Copahuevolcano based on the analysis, interpretation, and mapping of its products. Tenlithofacies are described on the eastern flank of Copahue volcano exhibiting several examples ofglaciovolcanism. The evolution of the Copahue volcano can be divided into twomain sequences: the Ancient Sequence (S1) and the Young Sequence (S2),separated by a major erosive phase. The S1 (early-middle Pleistocene-latePleistocene) consists of an initial subaerial effusive stage followed by amajor glaciovolcanic stage, during which a thick ice cap existed and the edifice grew beneath an englacial lake withthe eventual formation of a lava-fed delta. The S2 (late Pleistocene-Present)is defined by mainly effusive activity duringperiods of glacial advance and retreat recorded by an alternation of unconfined subaerial lavas and ice-confined lavas. The evolution of the Copahuevolcano therefore indicates two glaciations in the Copahue-Caviahue area duringthe late Pleistocene, in contrast to a single glaciation. Based on the glacialhistory in the areawe associate the first glaciation with the end of Marine Isotope Stage 3(57?29 ka) and/or the Last Glacial Maximumperiod (26.5?19.0 ka), and the second less-extensiveglacial period with the Antarctic Cold Reversal (14.5?12.9 ka).