Deciphering lake and maar geometries from seismic refraction and reflection surveys in Laguna Potrok Aike (southern Patagonia, Argentina)

• Published in: Journal of volcanology and geothermal research 2011-04, Vol.201 (1), p.357-363
• Main Authors: Gebhardt, A.C., De Batist, M., Niessen, F., Anselmetti, F.S., Ariztegui, D., Haberzettl, T., Kopsch, C., Ohlendorf, C., Zolitschka, B.
• Format: Article
• Language: English
• Subjects: explosive volcanism; Freshwater; maars; PASADO project; sedimentary basin processes; South America
• ISSN: 0377-0273; 1872-6097
• DOI: 10.1016/j.jvolgeores.2010.12.019

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. ► Seismic refraction and reflection data reveal shape of Laguna Potrok Aike maar. ► 370 m of lacustrine sediments underlain by volcanoclastic infill. ► Sparker data allow mapping of funnel-shaped crater wall discordance. ► Maar geometries and seismicall inferred lithologies are well comparable to other maars.