Reconstruction of the Holocene seismotectonic activity of the Southern Andes from seismites recorded in Lago Icalma, Chile, 39°S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Sébastien Bertrand a, 1, * , François Charlet b , Emmanuel Chapron b, c , Nathalie Fagel a and Marc De Batist b a Clays and Paleoclimate Research Unit, Department of Geology, University of Liège, Allée du 6 août, B18, 4000 Liège, Belgium b Renard Centre of Marine Geology (RCMG), University of Ghent, 9000 Ghent, Belgium c Geological Institute, ETH Zentrum, Zürich, Switzerland 1 Present address: Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS#25, MA 02543, Woods Hole, USA * Corresponding author, e-mail: sbertrand@whoi.edu, tel: +1-508.289.3410, fax: +1-508.457.2193 Abstract South-central Chile is one of the most geodynamically active areas in the world, characterised by frequent volcanic eruptions and numerous earthquakes, which are both recorded in lake sediments. In Lago Icalma (39°S), long piston and short gravity coring, as well as 3.5 kHz high-resolution seismic profiling, has been carried out in order to study the Holocene sedimentary infill of the lake, with a special focus on earthquake-triggered deposits. Macroscopic description of sediment cores and detailed grain-size analyses allow us to identify four types of seismically-induced deposits, or “seismites”: slump deposits, chaotic deposits, turbidites s.s. and homogenites. Homogenites are characterized by the occurrence of three distinct units on grain-size profiles (coarse base, thick homogenous unit topped by a thin layer of very fine sediment) and by the typical distribution of the grain-size parameters in a skewness-sorting diagram, while turbidites s.s. are characterized by a continuous fining upward trend.