Abstract

WINOCUR, Diego A.; BENITEZ, Anahí  and  BARBERO, Iván. Neotectonic evidence in the inner section of the Malargüe Fold-and-Thrust Belt, Grande river valley, Mendoza, Argentina. Bol. Soc. Geol. Mex [online]. 2021, vol.73, n.2, 00010.  Epub Jan 31, 2022. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2021v73n2a201220.

This work exposes some features of the landscape that enable us to determine neotectonic activity in the internal sector of the cordillera (35°30'S - 70°15'W). Through field observations, there were recognized lacustrine deposits characterized by laminated sands, silts, and clays, which records the sedimentation in a paleolake during a stage of the Last Glacial Maximum. The age of the deposits is inferred from their position in relation to a frontal moraine attributed to the last glaciation. Based on a sedimentary profile in the lacustrine deposits, there are described soft-sediment deformation structures and tectonic faults, one of them named El Seguro fault, presents 4 m of displacement measured along the fault plane, and an inverse movement. Morphologicalfeatures indicate a seismic trigger, proposing the activity of the fault as a possible source. The frequency and distribution of >0.1 km2 mass movement deposits and their location close to the active structures allow us to identify an accumulation of landslides around them. Although many factors have favored these movements as lithology, steep slopes and pos-glacial relief, their position in the landscape suggest that seismic activity accelerated the develoopment of large mass movements. Finally, it is proposed that tectonic activity has taken place during the Pleistocene-Holocene inclusive, with earthquakes of magnitude Ms ≥ 6, so that El Seguro fault could be an active fault at present.

Keywords : liquefaction; earthquakes; neotectonics; megaland-slides; last glacial maximum; Malargüe.

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