Abstract

PENNA, Ivanna M; HERM ANNS, Reginald L  and  GONZALEZ, María Paz. Natural dams in the headwater of the Lileo valley (Neuquén province, Argentina). Rev. Asoc. Geol. Argent. [online]. 2012, vol.69, n.3, pp.372-381. ISSN 0004-4822.

In this paper we analyze three natural dams that formed by deposits of mass movement that took place in the headwater of Lileo creek (Cordillera de los Andes, northern Neuquén, Argentina), two of them occurred in the last 50 years. The first one happened in the Holocene, by detachment of 0.14 km³ of volcanites in the western side of the valley, near the headwater of the La Tregua creek. This blockade originated a permanent water body of 0.44 km². The deposition in the 60's of a debris avalanche, originated in the slope of the valley opposite the scarp of the rock avalanche, occluded the breach carved by fluvial erosion in the rock avalanche deposit, generating a second water body of ephemeral type. The last dam, that took place between >1962- < 1985, was caused by a sudden progradation of a conoid developed in the mouth of La Tregua creek, due to an important contribution of material by a debris flow originated in the same zone of detachment as the aforementioned case. The continuous deposition of material in the conoid zone has buried the poles of the Loma de la Lata - Talcahuano gas pipeline, built in 1998. As the zone of detachment of the eastern side of La Tregua valley shows signs of instability, we consider it is possible that a new mass movement may cause another dam.

Keywords : Landslide dams; Mass movements; Neuquén.

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