Unraveling the timing of the Caviahue depression, Andean Southern Volcanic Zone: insights from the sedimentary infill

DEL PAPA, C.E; GUZMÁN, S.; HERNANDO, I. R.; EISERMANN, O.; BALBIS, C.; BUCHER, J.; GÖLLNER, P; PETRINOVIC, I.A.

INTERNATIONAL JOURNAL OF EARTH SCIENCES

SPRINGER

Lugar: Berlin; Año: 2020

1437-3254

TheCaviahue ? Copahue volcanic complex in the Southern Volcanic Zoneof the Andes is composed of the Pliocene ? Pleistocene Caviahuedepression and the active Copahue volcano. This volcanic complex islocated in a zone of profuse volcanic and tectonic activity, and thusthe origin of the depression includes both tectonic and volcanichypothesis (e.g. formation of a collapse caldera and a pull-apartbasin). According to current knowledge, the oldest rocks filling thedepression are lavas and ignimbrites of the Pleistocene Las MellizasFormation. However, clastic sedimentary deposits underlying this unithave been recognized. Here we document the characteristics of thesedeposits at the south shore of the Caviahue lake using field data anddigital outcrop models (DOM). We have concluded that the deposits aredeltaic and alluvial in origin and made up by a prodelta/distaldeltaic front, delta front deposits, delta plain sediments andalluvial deposits. An unconformity separates the deltaic depositsfrom overlying alluvial deposits, indicating the decrease in thestratigraphic base level probably associated to a suddencoarse-grained clastic input and a drop in the lake level. Our studyhas implications on the timing and evolution of the Caviahuedepression and indicates that the depression precedes the LasMellizas Formation. Thus, Las Mellizas ignimbrite should not beinterpreted as the main unit related to the Caviahue caldera as ithas been proposed by some authors. If the depression had indeed beenformed by a collapse caldera, this event would be previous to thedescribed sediments.p { margin-bottom: 0.25cm; line-height: 115% }