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Stratigraphy and sedimentary facies of lahar deposits at Chaitén volcano, Chile

Kyoko S. Kataoka 1, Aldo M. Umazano2,3, Kae Tsunematsu4, Rina Noguchi5, Pablo M. Villegas2,3

  • Affiliations: 1 Research Institute for Natural Hazards and Disaster Recovery, Niigata University, Japan; 2 INCITAP (CONICET-UNLPam), Argentina; 3Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Argentina; 4 Faculty of Science, Yamagata University, Japan; 5 Faculty of Science, Niigata University, Japan

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 157

  • Programme No: 3.5.16

  • Theme 3 > Session 5

Abstract

Chaitén volcano in southern Chile generated an explosive rhyolitic eruption in 2008--2009. Lahars with a complex combination of triggering factors and subsequent fluvial deposition of volcaniclastic sediments along the Blanco (Chaitén) River were associated with the eruption (Pierson et al., 2013; Umazano et al., 2014). The town of Chaitén is on the floodplain to delta plain approximately 10 km downstream from the volcano where the Blanco River flows into the Gulf of Corcovado, was impacted by the hazardous lahars and fluvial volcaniclastic sedimentation. Lahar deposits and fluvial volcaniclastic sediments during the past 800 years have been reported along the Blanco River (Lara et al., 2013; Umazano and Melchor, 2020). In this study, we investigated the lahar deposits and fluvial volcaniclastic deposits in the upstream of the Blanco River basin, part of which have not been described in previous studies. At least four depositional sequences are recognised,intercalated with paleosol layers; these consist of different types of flow deposits including hyperconcentrated flow deposits (sequence 4 lower), deposits with scour-and-fill structures (sequence 4 upper), muddy debris flow deposits (sequence 3), aggradational deposits with low-angle cross-stratification (sequence 2), and 2008--2009 pyroclastic density currents and lahar deposits (sequence 1). The present study reports newly obtained 14C ages in the sedimentary succession including lahar deposits in the delta plain area. We further discuss the stratigraphy and correlation of these deposits and their relationship to the previous eruptions and repetitive lahar generation.