Abstract
Tsunamis are unpredictable, catastrophic events, and so present enormous difficulties for direct studies in the field or laboratory. However, their sedimentary deposits yield evidence of a wide variety of hydrodynamic conditions caused by flow transformations on a spatial and temporal scale. Tsunami deposits ranging from the Miocene to modern times identified at different localities along the Chilean coast are described to provide a database of their characteristics. Among the typical features associated with tsunami deposits are well-rounded megaclasts eroded from coastal alluvial fans or beaches by very dense, competent flows. Sand injections from the base of these flows into the substrate indicate very high dynamic pressures, whereas basal shear carpets suggest hyperconcentrated, highly sheared flows. Turbulence develops in front of advancing debris flows, as indicated by megaflutes at the base of scoured channels.
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Acknowledgements
This investigation was funded by Projects FONDECYT 1010691, PCCI CONICYT-IRD (Estudio Sísmico de Alta Resolución del Relleno Sedimentario Holoceno de la Bahía de Mejillones del Sur: Implicancias Neotectónicas y Océano-climáticas), PRODAC (Universidad de Chile), Programa de Cooperación Científica Internacional (Conicyt), and IRD (Paleótropique), which are gratefully acknowledged.
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Le Roux, J.P., Vargas, G. Hydraulic behavior of tsunami backflows: insights from their modern and ancient deposits. Environ Geol 49, 65–75 (2005). https://doi.org/10.1007/s00254-005-0059-2
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DOI: https://doi.org/10.1007/s00254-005-0059-2