Unraveling the timing of the Caviahue depression, Andean Southern Volcanic Zone: insights from the sedimentary infill
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ORIGINAL PAPER
Unraveling the timing of the Caviahue depression, Andean Southern Volcanic Zone: insights from the sedimentary infill I. R. Hernando1 · J. Bucher1 · C. E. del Papa2 · J. O. Eisermann3 · P. L. Göllner3 · S. R. Guzmán4 · C. Balbis2 · I. A. Petrinovic2 Received: 10 April 2020 / Accepted: 11 September 2020 © Geologische Vereinigung e.V. (GV) 2020
Abstract The Caviahue–Copahue volcanic complex in the Southern Volcanic Zone of the Andes is composed of the Pliocene–Pleistocene Caviahue depression and the active Copahue volcano. This volcanic complex is located in a zone of profuse volcanic and tectonic activity, and thus, the origin of the depression includes both tectonic and volcanic hypothesis (e.g., formation of a collapse caldera and a pull-apart basin). According to current knowledge, the oldest rocks filling the depression are lavas and ignimbrites of the Pleistocene Las Mellizas Formation. However, clastic sedimentary deposits underlying this unit have been recognized. Here, we document the characteristics of these deposits at the south shore of the Caviahue lake using field data and digital outcrop models (DOM). We have concluded that the deposits are deltaic and alluvial in origin and made up by a prodelta/distal deltaic front, delta front deposits, delta plain sediments and alluvial deposits. An unconformity separates the deltaic deposits from overlying alluvial deposits, indicating the decrease in the stratigraphic base level probably associated with a sudden coarse-grained clastic input and a drop in the lake level. Our study has implications on the timing and evolution of the Caviahue depression and indicates that the depression precedes the Las Mellizas Formation. Thus, Las Mellizas ignimbrite should not be interpreted as the main unit related to the Caviahue caldera as it has been proposed by some authors. If the depression had indeed been formed by a collapse caldera, this event would be previous to the described sediments. Keywords Deltaic deposits · Alluvial deposits · Caviahue depression · Volcanic activity
Introduction The Pliocene–Quaternary Caviahue–Copahue volcanic complex is located in the Southern Volcanic Zone (SVZ) of the Andes (33°–46° S), ~ 30 km east of the Quaternary volcanic arc front (Fig. 1a; Muñoz and Stern 1988). Distinctive * I. R. Hernando [email protected] 1
Centro de Investigaciones Geológicas (CIG), CONICETUNLP, Diagonal 113 No. 275, B1904DPK La Plata, Argentina
2
Centro de Investigaciones en Ciencias de la Tierra (CICTERRA), UNC-CONICET, Av. Vélez Sarfield 1611, X5016GCA Córdoba, Argentina
3
Institut für Geologie, Universität Hamburg, Bundesstraße 55, 20146 Hamburg, Germany
4
Instituto de Bio y Geociencias del NOA (IBIGEO), UNSa-CONICET, 9 de Julio 14, 4405 Rosario de Lerma, Salta, Argentina
features of this volcanic complex are the 14 × 18 km rectangular Caviahue depression, with topographic walls with an average height of 600 m, also known as Agrio or Caviahue caldera (Pesce 1989; Linares et al. 1999; Mazzoni and Licitra 2000
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