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You are here: Home / Library / RBINS Staff Publications / The sedimentary record of the tsunami caused by the 1960 Great Chilean Earthquake in two coastal lakes on Chiloé Island, Chile

Philipp Kempf, Jasper Moernaut, Maarten Van Daele, Flor Vermassen, Willem Vandoorne, Mario Pino, Roberto Urrutia and Marc De Batist (2015)

The sedimentary record of the tsunami caused by the 1960 Great Chilean Earthquake in two coastal lakes on Chiloé Island, Chile

Sedimentology, 328:73-86.

This study describes sediments deposited by the tsunami following the 1960 Great Chilean Earthquake (MW 9.5) in two coastal lakes, Lakes Cucao and Huelde, on the west coast of Isla de Chiloé, south central Chile (42.6°S). Sub- bottom profiles and side scan sonar mosaics illustrate the sedimentary context of transects of gravity cores. The stratigraphy of both lakes features gyttja sedimentation, interrupted by the abrupt emplacement of a sandy layer with mud rip-up clasts and a mud cap. This sandy layer reflects a sudden change in sedimentary environment, most probably caused by a high-energy inundation. Radionuclide analyses (137Cs and 210Pb) date the inundation deposit to shortly before the mid 1960s. The only known event that matches the sedimentological and chrono- logical criteria is the AD 1960 tsunami. Using grain size analysis and comparisons with samples from modern en- vironments, we demonstrate that the proximal (seaward) part of the deposit consists of a mixture of sand derived from subaerial sources and reworked gyttja lake sediment. In the distal (landward) part of Lake Cucao, the sand component is lost and the deposit consists entirely of remobilised lake sediments. The repetition of tsu- nami deposit sequences in Lake Huelde suggests a minimum of three inundating waves. Sub-bottom profiles and side scan sonar mosaics reveal tsunami inundation over the barrier and more prominently through the outlet river channel. The dominant role of the river channel as a pathway for sediment transport is also described in core samples by tsunami deposits that fine away from the channel mouth. The identification and description of the deposit left by a known tsunami provide important insights into tsunami sedimentation in coastal lakes and have the potential to help in the search for paleotsunami evidence.
1960 Great Chilean Earthquake, 1960 great chilean earthquake, Sub-bottom profiles, Tsunami deposits, Coastal lakes, Grain size analysis, Side scan sonar

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