Deciphering lake and maar geometries from seismic refraction and reflection surveys in Laguna Potrok Aike (southern Patagonia, Argentina)
Gebhardt, A. C.; De Batist, M.; Niessen, F.; Anselmetti, F. S.; Ariztegui, D.; Haberzettl, T.; Kopsch, C.; Ohlendorf, C.; Zolitschka, B. (2011). Deciphering lake and maar geometries from seismic refraction and reflection surveys in Laguna Potrok Aike (southern Patagonia, Argentina). J. Volcanol. Geotherm. Res. 201(1-4): 357-363. dx.doi.org/10.1016/j.jvolgeores.2010.12.019
In: Journal of volcanology and geothermal research. ELSEVIER SCIENCE BV: Amsterdam. ISSN 0377-0273; e-ISSN 1872-6097
Laguna Potrok Aike is a bowl-shaped maar lake in southern Patagonia, Argentina, with a present mean diameter of ~ 3.5 km and a maximum water depth of ~ 100 m. Seismic surveys were carried out between 2003 and 2005 in order to get a deeper knowledge on the lake sediments and the deeper basin geometries. A raytracing model of the Laguna Potrok Aike basin was calculated based on refraction data while sparker data were additionally used to identify the crater-wall discordance and thus the upper outer shape of the maar structure. The combined data sets show a rather steep funnel-shaped structure embedded in the surrounding Santa Cruz Formation that resembles other well-known maar structures. The infill consists of up to 370 m lacustrine sediments underlain by probably volcanoclastic sediments of unknown thickness. The lacustrine sediments show a subdivision into two sub-units: (a) the upper with seismic velocities between 1500 and 1800 m s- 1, interpreted as unconsolidated muds, and (b) the lower with higher seismic velocities of up to 2350 m s- 1, interpreted as lacustrine sediments intercalated with mass transport deposits of different lithology and/or coarser-grained sediments. The postulated volcanoclastic layer has acoustic velocities of > 2400 m s- 1. The lake sediments were recently drilled within the PASADO project in the framework of the International Continental Scientific Drilling Program (ICDP). Cores penetrated through lacustrine unconsolidated sediments down to a depth of ~ 100 m below lake floor. This minimal thickness for the unconsolidated and low-velocity lithologies is in good agreement with our raytracing model.
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