Improving the facies model for syn-eruptive fluvial successions: lessons from the Chaitén volcano and Blanco river, Chile

UMAZANO, ALDO MARTÍN; BEDATOU, EMILIO; KRAUSE, JAVIER MARCELO; BELLOSI, EDUARDO S.; VILLEGAS, PABLO MARTÍN

Latin American Journal of Sedimentology and Basin Analysis

Asociación Argentina de Sedimentología

Lugar: La Plata; Año: 2022 vol. 29 p. 61 - 65

1669-7316

Typically, the stratigraphic record of syn-eruptive fluvial successions is apyroclastic-rich one. It includes an alternation of braided channel deposits andsheet-like floodplain strata, in which the occurrence of paleosols with in situ treesand primary pyroclastic deposits is common. The participation of facies formedfrom sediment-laden flows is also a conspicuous feature in these successions.Nevertheless, the disturbances occurred in the chilean Blanco River in 2008,as a consequence of the large tephra influx from the Chaitén Volcano eruption,result in discrepancies with the mentioned conceptual background includingthe plan-view form and filling of channels, and lateral compositional changesalong the river. These discrepancies would response to local conditions such asprecipitation, vegetation, topography, and type and amount of available sediment.Furthermore, the connection between the Blanco River and the Pacific Ocean,adds an additional feature to syn-eruptive fluvial successions, represented byassociated delta plain deposits composed of volcaniclastic sands.