Reconstruction of the Holocene seismotectonic activity of the Southern Andes from seismites recorded in Lago Icalma, Chile, 39°S
De Batist, Marc
MetadataShow full item record
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. Radiocarbon, 210Pb dating, and tephrochronology allow us to demonstrate that the regional seismotectonic activity was probably very high between 2200 and 3000 cal. yr. BP as well as between 7000 and 8000 cal. yr. BP and that none of the historically documented earthquakes have triggered any seismite in Lago Icalma. The most recent seismite recognized in the sediments of Lago Icalma is a slump deposit dated at 1100 ± 100 AD, i.e. older than the period covered by historical records. The remarkable record of seismites between 2200 and 3000 cal. yr. BP is probably influenced by a major eruption of Sollipulli volcano at 3000 cal. yr. BP, which has rejuvenated the stock of terrigenous particles available for erosion, by depositing a thick layer of pumices all over the watershed of Lago Icalma and by clearing the vegetation covering the volcanic ash soils. This paper demonstrates that the record of seismically-triggered deposits in lake sediments is not only controlled by the intensity of the triggering earthquake and the occurrence of unstable sediment along the lake slopes but also by the presence of particles available for erosion/remobilisation in the watershed.
Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 259 (2008): 301-322, doi:10.1016/j.palaeo.2007.10.013.
Showing items related by title, author, creator and subject.
Perceptual stability during dramatic changes in olfactory bulb activation maps and dramatic declines in activation amplitudes Homma, Ryota; Cohen, Lawrence B.; Kosmidis, E. K.; Youngentob, S. L. (2007-03-30)We measured the concentration dependence of the ability of rats to identify odorants and compared these results with the calcium signals in the nerve terminals of the olfactory receptor neurons. Odorant identification ...
Cruise Report C-131 : Scientific activities aboard the SSV Corwith Cramer, Miami, FL - Rum Cay - Port Antonio - Roatan - Key West, February 8 to March 19, 1994 Bohrer, Richard N. (SEA Education Association, 1994-03)This cruise report summarizes the scientific activities aboard SSV Corwith Cramer during the Sea Education Association SEA Semester cruise C-131. The scientific program was designed to provide practical experience for ...
Cruise Report W-45 : scientific activities undertaken aboard R/V Westward, Key West - Woods Hole, April 11 - May 23, 1979 Gaines, Arthur G. (SEA Education Association, 1979-05)This cruise report outlines the scientific activities for the Strombus Expedition, the forty-fifth cruise of the R/V Westward. These activities fall into two separate categories which, however, serve each other: a ...